Thursday, October 4, 2007

Svr Wx & Chase (10/5 - 10/8) -- Update #1

Thursday Oct. 3 Update, 10:00 AM: Didn't get a chance to view last nights' model runs so I'm taking the time to do that this morning before all of the 12z runs of the GFS/NAM are in. Tonight and Tomorrow are both under risks for severe weather over the northern plains, mainly northwest Iowa and then points northward as a fairly strong warm front begins to take shape wit the aid of strong low level winds from the south. Those winds will pick up tonight and likely develop elevated storms along it, possibilities of large hail are the main threat with those storms. Areas of northern Iowa and southern MN as well as extreme areas of eastern SD seem to be in the best location for those. The storms will likely continue into the day on Friday as the warm front lifts further to the north, potentially hampering some of the potential for severe weather on Friday evening. However the strengthening low in SD and warm front over northern SD and into MN will be the focus for potentially significant severe weather nonetheless. The areas of SD and west-central MN should be out of the clouds and allow significant warming, creating ample instability. Shear will also be there along the sharp warm front and low pressure system, the only negative will likely be the warm temperatures that create a cap over the area. If storms can push through that though, expect the potential for some large hail, damaging winds and tornadoes. The SPC has kept wording in their discussion on how some strong tornadoes may occur, so this deserves to be watched. I'm tied up for Friday night, so no chasing will take place despite the urge to take the chance...

Saturdays' threat is now being displayed fairly well by the models from last night, the NAM, GFS & ECMWF all have the trough position in a fairly consistent area. The strength is just slight stronger on the NAM than the others, but nothing tremendously different. The threat for Saturday though doesn't look tremendous, no surface low pressure system really has occurred along the trough that is beginning to push onto the plains. This is going to kind of spread the focus out to be along the stationary or quasi-stationary front over the Dakotas southward through Kansas. Looking like more of a hail/wind event with more broken line or lines of storms than individual cells. Things could change, but for now it looks like I'll enjoy the wonderful weekend weather here in Iowa.

Sunday however from last nights' runs looks like it could be quite the show if things fall together right. Both the GFS & ECMWF have similar upper level lows in terms of strength and position, GFS slightly south. The low pressure system begins to stack a bit, and is definitely cutoff even by Sunday evening over western/central NE. Plenty of shear to go along with that, however several negatives jump into my mind currently. The lack of a cap near the low which may lead to numerous clouds/showers before the evening and thus ruin some of the instability. If we can have a good warm sector though, the areas of eastern NE/eastern KS are definitely within an area that could have some very nice severe weather. This day is open to chasing with a couple others, so it'll be a day of interest as well.

The remainder of the week for this system is still somewhat up in the air, as the low becomes stacked and is likely to slowly meander across the rest of the plains state on Monday & Tuesday. There may be some severe threat still with the system, but it's hard to say how severe and what type of severe weather may occur. These days aren't likely to have me heading out anywhere unless it is right around Ames, thus not too concerned about the work week forecast.