Tuesday, October 16, 2007

Severe weather possible Thursday


A trough is forecast to move across the middle part of the US and become more negatively-tilted with time. If this occurs it will enhance the possibility of wind shear. Preceding the trough will be increasingly warm and moist air flowing northward from the Gulf of Mexico. This will contribute to increased instability in the South by Thursday. The Storm Prediction Center currently places most of the Midwest and South under a slight risk for severe weather on Thursday. Much of Illinois and Indiana have already been placed under a moderate risk. Forecaster Goss at the SPC said in this morning's "Day 3 Convective Outlook" that the moderate risk area might "be expanded to include areas as far south as the Gulf Coast states in later forecasts."

I will be posting much more later as the situation unfolds.

AFD From the NWS Huntsville this morning:
.LONGER TERM (WEDNESDAY NIGHT THROUGH MONDAY)...
FOCUS WILL BE ON THE POTENTIALLY ACTIVE CONVECTIVE
EVENT WED NIGHTINTO THURSDAY EVENING. THE SPC DAY
3 CONVECTIVE OUTLOOK INCLUDES A SLIGHT RISK OF SEVERE
STORMS...AND WE CANNOT DISAGREE AT THIS POINT.
WE HAVE
NOW SEEN FAIRLY GOOD RUN TO RUN CONSISTENCY
INPROGGING A SIGNIFICANT TROF AND COLD FRONT INTO A
FAIRLY MOIST...UNSTABLE AND HIGH SHEAR ENVIRONMENT

THURSDAY.WED NIGHT INTO THURSDAY WILL BE
CHARACTERIZED BY A STRONG LLJ (UPWARDS OF 40-50KT)
PROVIDING HIGH MAGNITUDE MOISTURE TRANSPORT INTO
THE REGION. THIS IS IN ADVANCE OF A STRONG UPPER JET
ROUNDING THE BASE OF AN UPPER TROF THAT GENERATES
A STRONG SFC CYCLONE OVER THE UPPER MS VALLEY. A
TRAILING COLD FRONT WILL SLICE INTO TROPICAL AND
UNSTABLE ENVIRONMENT THURSDAY EVENING.
DEEP
LAYER AND LOW LEVEL SHEAR PROFILES APPEAR QUITE
FAVORABLE TO SUSTAIN SUPERCELLS
. AREA WILL BE
BENEATH RRQ OF 100-120KT UPPER JET MAX. EXTENSIVE
SHRA AND ELEVATED TSRA SHOULD BE ONGOING
THURSDAY MORNING AS THE WARM FRONT LIFTS NE.
THE GFS DEVELOPS ANOTHER GULF WAVE WHICH MOVES
RAPIDLY NE THRU AL INTO GA THURSDAY MORNING...
WHICH COULD FURTHER ENHANCE PRECIPITATION...BUT
STILL UNSURE IF THIS WILL MANIFEST. THE SEVERE
THREAT SHOULD BE FAIRLY LOW EARLY THURSDAY GIVEN
MOIST LAPSE RATES. THE AIRMASS WILL BE TROPICAL
EXHIBITING A HIGH SHEAR/LOW CAPE ENVIRONMENT. AS
THE WARM SECTOR SPREADS N...FORECAST SOUNDINGS
REFLECT LOW LEVEL LAPSE RATES STEEPENING DURING
THE AFTERNOON HOURS. USING THE SOUNDING TOOLKIT
FOR KMSL(MUSCLE SHOALS)...
GFS OUTPUT REFLECTS WARM
SECTOR SB-CAPES NEAR 1400J/KG....0-1KM SRH NEAR 100
M2/S2 BY LATE AFTERNOON
. THIS PER FORECAST TEMP IN
THE L80S AND DEW POINTS IN THE U60S...BUT WILL HINGE
GREATLY ON THE EXTENSIVE CLOUDINESS THAT MAY EXIST.
15/21ZSREF PROBABILITIES OF 1000+ CAPE EXCEED 60 PCNT
BY 21Z IN THE WARM SECTOR.
THE NAM IS SHOWING "GRID
SCALE" CELLS/ STORMS ALONG THE COLD FRONT ALONG
THE MS RIVER THURSDAY AFTERNOON WHICH SHOULD
ADVANCE RAPIDLY NE INTO THE LOCAL AREA BETWEEN 03-
06Z
. THIS WITHIN AN AREA OF SIGSVR NUMBERS PROGGED
AT 30000-40000 M3/S3. THIS AREA SHIFTS E THROUGH THE
TN VALLEY THURSDAY EVENING...WITH VALUES DROPPING
TO THE 20000-30000 RANGE.
SUPERCELLS CERTAINLY LOOK
TO BE A THREAT.TORNADO THREAT INCREASES AS WELL
GIVEN THE COMBO OF A HIGH LOW LEVELSHEAR AND
MODERATE LOW LEVEL CAPE ENVIRONMENTS
. HOWEVER
TIME OF DAY MAY LIMIT THIS DURING THE EVENING HOURS.
BY 00Z AT KMSL...THE GFS SOUNDING SHOWS A 0-1KM SRH OF
~180 M2/S2. HIGHEST POPS...IN THE LIKELY CATEGORY...WILL
BE PLACED THURSDAY EVENING AHEAD OF THE COLD FRONT.
AREA RESIDENTS...MEDIA...EMERGENCY MANAGEMENT AND
SKYWARN NETWORKS SHOULD PAY CLOSE ATTENTION TO
THIS WEATHER SITUATION THE NEXT COUPLE OF DAYS. ON
THAT NOTE...WEDNESDAY IS FALL SEVERE WEATHER
AWARENESS DAY IN ALABAMA AND TENNESSEE...SERVING
AS A GOOD REMINDER TO BEPREPARED.

4 comments:

Rick said...

You guys are in a better set up than us. But like you said the SPC may move that moderate rating further toward us. I look at this huge slight risk area and have seen this in the past. It is like trying to pin something down on a local level but with a broad stroke to cover half the country.
Well, if there is severe weather they wont have missed it.

Mike said...

I think it might be narrowed down some by Thursday. It is projected to be a broad trough though.

Dewdrop said...

It's show time!!! Get that camera ready, Mike!!!!

Mike said...

I've got to get everything ready. Plus I have to hope and pray I get out of court on time. It's a case I am covering for a vacationing worker and I hate to pass it off to anyone else. Plus I will have my boys that evening. Maybe we'll see something interesting!