5/8/08 FCST: MO/AR/IL/KY/TN/MS

[beaudodson]

The GFS is showing a deep low pressure area pulling out of the central Plains. As of 12z Saturday Morning the GFS and EC both show a similar set-up. The EC indicates a 980-990 low tracking through the Oklahoma Panhandle and Southern Kansas and then moving eastward into Missouri. The GFS (see images below) shows a deep low moving across Kansas and into Missouri and Illinois. A strong dry line sweeps through Oklahoma and Texas on Wednesday night and then pushes into the Missouri Valley on Thursday.

CAPE indexes appear to be sufficient on Thursday for severe thunderstorms to break out along and ahead of the front. The 500mb wind map shows a negative tilt - not the strongest wind fields though on the 500mb map. We will have to watch and see what the trend is on those fields.

A squall line with perhaps supercells ahead of it seems fairly likely on Thursday. PWV's are around 1.50" over St Louis. There is some question as to just how much return flow there will be. Both CAPE and the dew point fields are a bit skinny, however, not too far different from Friday's event (May 2nd). GFS is showing low to mid 60 dew points from the gulf coast into central Illinois.

One item to note is that the GFS would stall the front west of Missouri for about 36-48 hours. This will give a bit more time for moisture to return north. Same for other areas further east.

I believe, that if the GFS and EC are correct, that we see a decent event shaping up over areas that were just hit hard by storms on Friday.

GFS Pressure combined with dew points (maps below show you the forecast track for the area of low pressure along with the dry line/frontal system)...

Thursday Morning 6z
Thursday Morning 12z
Thursday Afternoon 18z

850 mb wind fields indicate a broad area of 35-55 mph across OK/MO/AR/IL on Thursday Morning (early). The negative on the GFS is that the wind fields decrease through the day on Wednesday. The 500mb maps indicate the storm may not intensity much during the day as it pulls northeastward (unsure on where this storm would occlude).

The GFS does show an enhanced area of 850 mb winds across East Arkansas, West Kentucky, West Tennessee, and Southern Illinois, at 18z Thursday.

GFS would indicate morning convection across East Missouri moving into Illinois. Then a chance for regeneration during the afternoon. This is getting into the finer details - which is a bit early to be forecasting. Exact storm track will likely change in the coming days - still a bit of time to fine tune the forecast.

 

[beaudodson]

Monday's forecast models show a trend to shove the low pressure area a bit further south. Both the NAM and the GFS take the primary low across Southern Missouri and Northern Arkansas. Alabama may need to be added to the thread.

It appears that the greatest instability on the models is going to be placed over Mississippi and Alabama. Thursday afternoon could be rough in both areas. Further north is problematic with the track of the low and instability.

CAPE values are sufficient for severe weather across the gulf coast states.

 

[tom hanlon]

We seem to need to modify the subject of this forecast to include North Carolina and Alabama. I am trying to figure out if the narrow zone of chaseable terrain is worth it in both areas.

Shear is available, if clearing occurs we could have enough CAPE also.

I will monitor the North Carolina region and perhaps pick a target this evening. As for Alabama, is it chaseable ?

From the Raleigh NC HWO.

[FONT=lucida sans typewriter, lucida console, courier]A FEW STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED LATE THURSDAY
AND THURSDAY NIGHT. THE MAIN SEVERE WEATHER THREAT WILL BE
DAMAGING WINDS AND LARGE HAIL. AN ISOLATED TORNADO MAY ALSO OCCUR.[/FONT]
--
Tom Hanlon