Wednesday, April 29, 2009

Another Rainy Day

Another rainy day may be in store for the state as a cold front pushes over the state tomorrow. A few thunderstorms are possible across southern and eastern Iowa tomorrow, with the slight chance of a severe thunderstorm capable of large hail. Otherwise another soaking rain expected for the fields of Iowa, which appear highly un-planted at the moment.

Total precipitation amounts are expected to range from a tenth to a quarter of an inch across western Iowa through tomorrow afternoon. Eastern Iowa may see more, ranging from a few tenths to a half-inch of rain expected for those areas through tomorrow night.

Lows tonight in the 50s across the state, with highs tomorrow ranging from near 60 to near 70 from northwest to southeast. Thursday night lows behind the cold front should range from the upper 30s across northwest Iowa, to near 50 in the extreme southeast as the cold front is just passing through. Friday highs in the upper 50s and lower 60s across the entire state as mostly cloudy skies continue. Friday night lows in the mid 30s to mid 40s from northwest to southeast as skies begin to clear for the weekend. Temperatures will be on the rise through the weekend and into early next week before our next storm system moves in mid-week next week. It looks like we'll finally have a nice and dry weekend across the state!

Monday, April 27, 2009

Heavy Rain

The heavy rains that continued through much of the nighttime hours created quite the flooding conditions across the state. Currently it appears that 28 counties are under a flood warning for rivers/streams that are above or forecasted to be above flood stage in the coming hours. Most flooding is minor at this time, with only a few locations forecasted to see moderate flooding for a short time. A look at the observed precipitation for the 24 hours previous to 7 AM this morning across Iowa:

A mix of clouds and light showers expected today, with temperatures only expected in the 50s to lower 60s in a few locations. Look for more sunshine and warming temperatures through mid-week. More details on the weeks forecast in tonight's update!

Sunday, April 26, 2009

Severe Weather Recap: April 26

Although thunderstorms are continuing to move across central and eastern Iowa, it appears as if our severe weather threat has become minimal. A few of the thunderstorms entering southern Iowa may have the potential to produce some gusty winds as they continue northeast; otherwise the main threat will be the heavy rains causing flash flooding of low-lying areas.

Both a severe thunderstorm watch and tornado watch were issued for areas of the state today, both of which have now been canceled. Several clusters and line segments of thunderstorm moved across the state, with a majority of reports across central Iowa coming in the form of damaging winds. There was isolated development of a supercell in northeast Iowa ahead of the more linear natured thunderstorms in central Iowa. This supercell did produce several reports of large hail varying from quarter sized to golf ball in diameter. This supercell also produced the first tornado(s) of the year for the state of Iowa, with four reports total coming out of northern Linn county and extreme southern Delaware county. This storm also produced another brief tornado just across the border in Wisconsin. At this time there has not been any significant damage reports with these tornado reports...

Heavy rains are causing flash flooding and flooding of low-lying areas across central and eastern Iowa. This threat will continue through tonight and into tomorrow as the rains continue. Expect the clouds to slowly move out of the area, leaving us will dull skies on Monday; but the sun will return for Tuesday.

Severe Weather: April 26

A warm front is lifting its' way north this morning and will continue to do so until later this afternoon. Currently this warm front in association with strong southerly low level jet is creating an ample environment for thunderstorms even this morning into early afternoon across western Iowa. The Storm Prediction Center has issued a Severe Thunderstorm Watch for western Iowa until 4 PM for the risk of large hail and damaging winds...

Severe Thunderstorm Watch #189

For more information please listen to local media and NWS throughout the day...

Saturday, April 25, 2009

Weekend Severe Weather

The bulk of great severe weather chances are likely to be confined to the TX/OK/KS areas both today and tomorrow with a dryline and triple point intersection and ample moisture/instability present. Plenty of chasers are out as we are on a weekend and we are nearing the time frame of May, which is southern/central plains chase heaven. The state of Iowa will try to get its' fair share of severe weather this early in the season too...

A quick recap of yesterday's (April 23) severe weather across the state: Several storms were able to become severe warned yesterday, however, as expected the depth of the moisture was a problem and we ended up with the large hail for the most part, along with a few gusty winds. Large hail ranging from dime to nickel sized, even a few quarters and slightly larger, were reported throughout southwest, central, and northeast Iowa.

Today's (April 24) severe weather threat across the state will be very limited as the cold front has slid through all but extreme southeast portions of the state. This small corner of Iowa may see some thunderstorm development this afternoon with the chance of some large hail and/or damaging winds with these thunderstorms. Light rain and cloudy skies are expected across the remainder of the state, as highs only reach into the upper 40s to mid 50s compared to the 80s and 90s the past two days!

Sunday will have severe weather once again likely across the state as the current cold front begins to move back north as a warm front tonight and through tomorrow. An associated low pressure system should develop and move across western Iowa into southern Minnesota by Sunday evening. There is still big questions in the threat of severe weather given that extensive cloud cover and rain showers may be over the state throughout the day on Sunday. If this does occur, thunderstorms are still likely to develop, however, with a limited severe weather threat of marginally severe hail and gusty winds. If areas of the state ahead of the cold front coming eastward and south of the warm front are able to clear in the afternoon, at least moderate instability should be expected with much better potential for severe weather. An additional quick update tomorrow morning may be available for tomorrow's severe weather threat in Iowa...

Friday, April 24, 2009

April 24 Severe Weather Update #1

The cold front continues to slowly sag southeast, currently located from Minneapolis southwest to Storm Lake and then south of Sioux City, near Hastings, NE and then near Goodland, KS per latest surface analysis. The frontal located around 4 PM will be the key, as anytime from that point on we may see initiation of thunderstorms. As mentioned the front is moving slowly southeast, thus still expect all but northwest and southeast corners to see good thunderstorms this evening/overnight.

Temperatures well into the 70s already, with dew points approaching 60; yielding 1000-2000 J/kg of surface based CAPE already. The depth of moisture is somewhat in question, as this mornings 12z radiosondes indicated that the good moisture had only reached as far north as Topeka, KS. Omaha sounding was very dry above 850hPa and with the low level jet already subsiding it seems questionable as to whether or not a good depth of moisture will reach well into Iowa. Nonetheless, thunderstorms are still likely to develop along the front and may be able to remain discrete for an hour or two before sunset. These initial discrete storms will be capable of large hail and damaging winds, and a minimal tornado threat. The tornado threat also appears minimized right now with little to no shear present, it does appear that at least meager values will be present this afternoon to warrant at least the mention.

Thunderstorms expected to evolve into line segments as the evening progresses, likely into one or more squall lines given strong unidirectional shear and relatively dry levels between 850-600 hPa. This will likely continue the threat for large hail and especially damaging winds across the state of Iowa as storms move northeastward.

I will not be chasing this event, nor any events this weekend as I have prior commitments. But, will be watching things closely and hopefully providing a few updates for those that wish to keep up to speed on things.

Thursday, April 23, 2009

Severe Weather: April 24

Latest NAM forecast is on its' way online, and with that I will update the forecast for tomorrow's severe weather threat. Cold front will be draped across the plains from northwest Kansas to northern Wisconsin tomorrow evening. This will leave much,if not all, of the state of Iowa in the warm sector with temperatures well into the 80s and potentially 90s once again. Surface winds from the south will continue to bring in moisture, likely nearing 60 degree dew points along the front. This should yield CAPE values ~2000 J/kg, and with the rapid surface warming and mixing much like today we may near convective temperatures. It does appear that any capping should be overcome by 00z tomorrow across much of Iowa along the front. If storms are able to break any capping between 21z and 00z these will be more discrete, thus capable of significant hail; and a tornadic storm cannot be ruled out given some of the storm-relative shear values just ahead of the front. The more likely scenario will be several clusters of storms to develop along the cold front during the evening hours, likely congealing into one or more MCS's as the night progresses. The large hail and damaging wind threat is fairly good given the instability and eventual shear with the low-level jet during the nighttime hours. Much of the state will be at risk for severe weather, but areas of central and southwest appear more likely at this time.

Additional updates are likely tomorrow morning.

Beyond Friday's threat, both Saturday and Sunday do appear to have very good chances of thunderstorms across at least the southeast half of the state as the cold front stalls and lays across the state throughout the weekend. The threat for severe weather does also appear for both days, however, the risk does not appear significant at this time with mainly a large hail and damaging wind threat.

Record Highs on April 23

Although nothing will become official until we go past midnight tonight, it would appear very likely that at least three cities saw record high temperatures this afternoon in northwest Iowa. Much of southern Iowa saw cloud cover this afternoon due to an impressive MCV (mesoscale convective vortex) that was initiated across eastern Kansas during the early morning hours and continued across northern Missouri throughout the day. The clouds across much of the south kept temperatures much cooler than expected, with highs only in the mid 70s to lower 80s. This is still well above normal for this time of year, thus nobody should really be complaining!

With clear skies, strong southerly winds, and ample mixing, the temperatures across northwest Iowa soared this afternoon with many stations reaching the mid 80s early in the afternoon. The following are details on the records that are likely to become official at the end of the day:

Sioux City, IA peaked at 3:46 PM this afternoon with a high of 92 degrees. This breaks the old record of 87 degrees that occurred in 1939!

Just previous to Sioux City's high, Sioux Center reached their peak of 89 degrees at 3:38 PM. This ties the previous record that was set in 1990.

Spencer, IA also went above the previous record that was set in 1990. The high today was 86 degrees, which was 2 degrees above the previous record.

Look for temperatures to once again reach into the 80s tomorrow, potentially hovering near the record mark for April 24!

Severe Weather Threat: Apr 23

A strong shortwave and associated vorticity maxima is currently located over extreme northeast Kansas and northwest Missouri. This shortwave should continue to move east/northeast during the day, continuing the threat of showers and thunderstorms over northern Missouri and southern Iowa. At this time it does not appear that these thunderstorms will be capable of severe weather given limited instability over this area. Further west a warm front will continue to push eastward, giving clear skies and temperatures in the 80s. Moisture advection is continuing into the area, however dew points only in the 50s are expected. Despite yielding some instability over western Iowa and eastern Nebraska, the atmosphere should be well capped and thus it appears that no thunderstorms are likely at this time through the remainder of the day. Thus today's severe weather threat appears very low throughout the entire state of Iowa.

Additional updates on today's threat will only be posted if conditions warrant.

Wednesday, April 22, 2009

Severe Weather: April 23/24

I'm going to focus on the rest of the work week and its' potential for severe weather before I get into the weekend in a later post. Currently the surprise event may be coming into shape for tomorrow evening across parts of the plains. A majority of models had indicated a shortwave that would move across the plains states during the day tomorrow and be across Iowa by the evening hours. However, many of the models had not initiated precipitation due to the stout inhibition (capping) that is in place. Some of the more recent model runs had finally broken this capping inversion and initiated some fairly heavy precipitation across parts of southern Iowa. So a quick overview of tomorrow's potential setup:

A warm front will likely be pulled eastward through the state during the early afternoon hours Thursday, leaving warm southerly flow to enter much of the western half of the state. Temperatures likely into the 80s and dew points in the upper 50s are likely, leaving 1000-1500 J/kg of CAPE over much of western Iowa and surrounding areas. Given other lower level temperatures, a capping inversion should be present for much of the day. With strong heating and mixing likely to occur, there appears to be a small probability that this inversion would be wore away and surface based convection could occur. Convective development would likely be aided by the 500hPa shortwave and associated vorticity maxima. Given marginal wind shear, any discrete storms may be able to be supercellular in nature; while more of a multicellular large hail threat may be more likely. An interesting setup nonetheless that will be monitored closely as we enter the day tomorrow and continue through the afternoon. If I were willing/able to chase I think the target area to hang out would be the Shenandoah, IA area. Additional updates are likely if the severe weather threat continues to materialize.

As for Friday, a cold front will push into the state from the northwest; in which very warm (potentially record) temperatures and dew points near 60 are likely to be in place. This should once again give way to 1000-2000 J/kg of CAPE across parts of Iowa and adjoining areas. It does once again appear to be capped as well, at least for regions ahead of the cold front. The most likely solution would be for elevated thunderstorms to occur along or just behind the front, capable of large hail through the evening and early nighttime hours across the western and northern thirds of the state. If temperatures are able to warm enough to initiate surface convection, there is the potential for discrete storms just ahead of the front which could be supercellular. Hard to believe we are talking about two days straight with capping issues in late April in Iowa, but we'll take what we can get for severe weather chances this early in the season. More details on Friday's threat in later updates after Thursday's potential becomes more defined.

Either way, enjoy the well above average and near record temperatures across the state the next two days!!

Severe Weather Threat: April 24-26

The large scale pattern is going to evolve into one that is favorable for severe weather, potentially widespread, for the plains state including Iowa. The latest SPC forecasts do indicate the potential for severe weather beginning Friday across much of the state; and then also over the weekend. More details on the severe weather chances in tonight's update...

For now here's a look at the latest SPC forecasts:

Tuesday, April 21, 2009

Let the Warm-up Begin!

Highs today ranged from the upper 50s across northeast and east-central Iowa to the upper 60s across the western portions of the state along the Missouri River. These highs should be on the rise through Friday, as we then see our first frontal system move into the state since this past weekend. While this system coming up may hold some fun potential for the weather lovers on the plains, as with such a long time between systems and the southerly flow throughout the week we are looking at the potential for another couple days of storm chasing! More details on the potential for severe weather in tomorrow's update...

Back to the happenings of today, April 21, the average highs range from the lower to mid 60s from north to south across the state. The record highs for this time of year are already approaching the 90 degree mark throughout the state; with record lows in the teens to mid 20s. Luckily we won't be talking about getting within 10 degrees of the record lows, but 10 degrees within the record high is a definite possibility for Thursday and Friday this week. Forecasts are still calling for increasing temperatures into the mid 60s to mid 70s from northeast to southwest tomorrow (Wednesday). Thursday's highs in the mid 70s to mid 80s from east to west; and Friday's highs in the mid 70s to mid 80s as well! Friday may be a bit cooler in some portions, mainly northwest, parts of the state as the frontal system begins to move in and may leave some cloud cover over the state on Friday afternoon which will hinder the high temperatures. Nonetheless, expect a very nice latter half of the work week for the entire state!

As mentioned, tomorrow's update will hopefully feature some details into the potential for thunderstorms and whether or not Iowa will be able to see some severe weather.

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Monday, April 20, 2009

Cooler Monday

Cloud cover and isolated showers kept temperatures a bit cooler today across parts of the state. Highs in the upper 40s and 50s across much of the northern two-thirds of Iowa were likely an artifact of the clouds and rain. The southern portions of the state did however see the sun throughout the afternoon, and despite the northwesterly winds they managed to reach into the upper 50s and lower 60s for highs this afternoon. As I mentioned in the previous sentence, the entire state saw strong northwesterly winds. Gusts in the 30s were common, with even a few sites in south-central Iowa seeing 41 mph gusts!

Look forward to rising temperatures through Thursday this week, as highs increase into the 60s tomorrow; 60s and 70s on Wednesday; and well into the 70s on Thursday. It was also brought to my attention today that The Weather Channel has been displaying forecasted temperatures well into the 80s!! This afternoon they still had a high of 88 for Ames later this week... While highs in the 80s across the state are certainly possible, I don't think we'll be seeing nearly 90 anytime this week. Just another reason that I like to tell people that The Weather Channel is terrible at forecasting!!

Sunday, April 19, 2009

Weekend Rain

With the final showers moving out of extreme eastern Iowa this morning, I figured we could have an update on just how much rain fell over the past 36 hours across the state. Previous forecasts had mainly called for a moderate, but steady rain across the state, with a few isolated thunderstorms potentially mixing in during the afternoon on Saturday. This seems to have held true with a few areas seeing amounts heavier than a quarter of an inch; but a majority seeing less than a tenth through the weekend. Although not an entire event view, the automated gauges throughout the state captured this much rain through Midnight last night.

Look for cloudy skies with a few sprinkles through the afternoon hours today, temperatures in the 50s throughout the state. Tomorrow and the remainder of the week look great, with clear skies and warming temperatures. It appears as if the state may see its' warmest temperatures of the year by late this week if the forecasts stays on track! More details on the warming trend in the next update!

Thursday, April 16, 2009

Weekend Wetness

After two great days of weather for most of the state with high temperatures in the 60s and 70s and clear skies we are looking at only one more day remaining. Friday highs should range from the upper 60s to lower 70s throughout the state, much like today. With southerly winds continuing, moisture should also slowing make a return into the state through Saturday. Friday night lows in the mid 40s to lower 50s are expected, with clouds on the increase through the night.

Weekend temperatures in the upper 50s to upper 60s from west to east on Saturday, with overnight lows in the 40s. Sunday's highs will be hampered by cloud cover and light rain, only making it into the 50s throughout. Overnight lows ranging from the mid 30s in the northwest to the lower 40s in the southeast. As mentioned, precipitation in the form of light to moderate rain is expected to begin on Saturday and continue through Sunday night in the eastern third of the state. Total precipitation amounts should range from a half-inch to an one and a half inches across the western and northern thirds of the state. A half-inch to an inch of precipitation is possible across the remainder of the state. As usual, some areas may see slightly less or more dependent upon the location of heavier showers.

We'll get out of the rain for the beginning of the work-week, with temperatures moderating throughout the week according to the latest forecasts. Our next big chance of precipitation after this weekend looks to come into shape for the following weekend...

Tuesday, April 14, 2009

Wonderful Weather

Highs today ranged from the 50s in extreme eastern Iowa, to the mid to upper 60s across the remainder of the state. These temperatures and clear sky conditions should continue for the remainder of the week! Wednesday's highs should range from near 60 to the upper 60s from northeast to southwest. Thursday's highs should be in the mid 60s for nearly the entire state, with northwest Iowa having the potential to be a bit lower as cloud cover moves in during the afternoon. Highs on Friday will increase even more as stronger southerly winds continue to bring up warmth and moisture ahead of our upcoming storm system for the weekend; expect temperatures in the mid to upper 60s across the state. Lows through the week will increase from the upper 30s to lower 40s on Wednesday, to the 40s on Thursday, and the mid 40s to lower 50s along the Missouri River on Friday night.

As we move into the weekend we'll see a storm system finally move off of the Rockies and onto the plains states. With the low pressure system likely tracking over the central plains, it'll leave Iowa in the deformation zone. This means light and continuous rain for much of the day on Saturday for a majority of the state. Saturday highs should range from the mid 50s to the mid 60s from northwest to southeast; with lows from near 40 to near 50. This rain should slowly move out of the state on Sunday, leaving heavy cloud cover, and high temperatures only in the lower to mid 50s. Total precipitation should range from a few tenths across northern Iowa to nearly an inch across central and southern Iowa.

Looking well ahead into next week, temperatures in the 50s to near 60 appear likely during the first half of the week. We should be able to stay clear of the precipitation for Monday, however, a few weak disturbances may give the state a shot of precipitation on Tuesday or Wednesday. Low temperatures in the mid 30s to near 40 should be seen during the first half of the week as well. More details on next week in later updates! Enjoy the week of warm and sunny weather!

Tuesday, April 7, 2009

The Return of Spring

This past weekends' winter storm left snowfall across all but extreme southern Iowa, with the highest amounts occurring in three different locations (northwest Iowa, extreme west-central Iowa, and central Iowa). The highest snowfall report came from Eldora, IA where a measured 10 inch snowfall was reported, this high snowfall came with some thunder and a total of 1.03" of liquid. For a quick overview of where the snow fell, take a look at the storm total map below:

Temperatures have increased over the past two days, but have been hampered in the areas where significant snowfall was received. With today's warm temperatures, the snowfall across much of the state has disappeared which will allow temperatures to warm even more in the coming days. A quick look at our upcoming high temperatures shows upper 40s to upper 50s from north to south likely on Wednesday. Thursday high temperatures from near 50 to the upper 50s from northwest to southeast; and Friday's high temperatures in the lower to mid 50s throughout the state. Expect some showers to work into the state for Thursday night and continue into Friday which will moderate temperatures some. The weekend looks similar, with another storm system working into the state for the late weekend could bring even more precipitation and some cooler temperatures.

Thursday, April 2, 2009

Winter Storm: April 4-5

Another potent storm system is taking shape to impact the state tremendously beginning Saturday evening and continuing into Sunday. The low pressure system is expected to track through southeast Iowa on Sunday, which will likely leave parts of the northern half of the state under a potentially heavy snowband. Many of the models have come into a consensus on the potential of 6-12 inches of snow, with some amounts even over a foot possible within this heavy snowband.

Although models are currently struggling with the exact timing and speed of this low pressure system, which will have an effect on the storm total amounts. The HPC (Hydrometeorological Prediction Center) does seem to have fairly good confidence in this system, as they issued their day 3 outlook with a moderate chance (>40%) of over a foot of snow on a band from south of Sioux City to the northeast through Mason City, etc...

An ironic forecast as the 13th Annual Severe Storms & Doppler Radar Conference got underway this afternoon in West Des Moines. Another update will likely be published tomorrow, good night from West Des Moines!