[LeArc] Forecast Discussion : MLI@ 4/17/2003 3:30:34 PM

[learc@mailman.qth.net]

The following weather message is provided by McDonough County E.S.D.A.


FXUS63 KDVN 172012
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
305 PM CDT THU APR 17 2003

UPPER TROUGH TO SLOWLY PULL EAST UP THE OH RVR VALLEY TONIGHT...WITH
BRIEF BOUT OF SFC RIDGING TO FOLLOW OVER THE AREA FOR A COOL
1ST PERIOD WITH LIGHT NORTH-NORTHEAST WIND. CLOUD COVER WILL LINGER
INTO AT LEAST FRI MORNING...AND WILL PRECLUDE ANY FOG DEVELOPMENT
WORTH MENTIONING. TEMPS WOULD BOTTOM OUT IN MID 30S IF IT WEREN'T FOR
THE CLOUD COVER...BUT WILL STILL SIDE WITH COOLER MAV FOR MOST OF THE
CWA(UPPER 30S-AROUND 40). SOME OF THE LOWER CLOUDS MAY CLEAR OUT
FOR FRI(BUT H8-H75 INVERSION MAY HAVE TRAPPING EFFECT TOO)...BUT
FEEL ENOUGH OF A MID AND HIGH DECK TO WARRANT MOSTLY CLOUDY WORDING.
EAST TO SOUTHEAST SFC FLOW WILL INCREASE AS DAY PROGRESSES NORTH OF
DEVELOPING WARM FRONT OVER MO. THIS FLOW NOT TO TAP INTO THE
MILDEST OF AIR-MASSES...BUT FEEL TEMPS SHOULD RECOVER INTO THE 60S
OVER MOST OF THE CWA...EXCEPT THE FAR EAST AND NORTHEAST WHICH MAY
STAY IN THE 50S.

LOOKS LIKE A DYNAMIC WEEKEND IN STORE FOR THE LOCAL AREA. SHORT
RANGE MODEL ENSEMBLE SUGGESTS A LARGE PIECE OF WAVE ENERGY TO ROLL
OUT OF SOUTHWEST CONUS L/W TROUGH AND BECOME NEG TILTED. IMPRESSIVE/
STRONGLY DIFFLUENT SOUTHWEST MID AND UPPER LEVEL FLOW TO FAN OUT OVER
THE AREA AHEAD OF THIS FEATURE BY FRIDAY EVENING...SETTING THE STAGE
FOR A TWO DAY PERIOD OF OCCASIONAL ROUNDS OF STRONG LIFT THROUGH THE
COLUMN...AS VORTS AND JET MAXES PROPAGATE UP THROUGH THIS FLOW.
PREFER GFS-AVN HANDLING OF BIT FURTHER SOUTH PLACEMENT OF DEVELOPING
SFC WARM FRONT AND LOW FRI NIGHT...AND WILL GENERALLY FOLLOW THROUGH
THE SHORTER RANGE. STRONGLY CONVERGENT LLVL THTA-E ADVECTION AND
CONVERGENCE...ALONG FORCING FROM WITH INITIAL VORT PIECE WILL LOOK
TO COME TOGETHER AND IGNITE ELEVATED CONVECTION OVER EASTERN NE
AND FAR SOUTHWEST IA FRI EVENING...WITH ACTIVITY THEN PROPAGATING
EAST AND NORTHEAST ACRS IA ON VEERING LLVL JET AND THTA-E FEED. AS
THIS ACTIVITY RUNS AWAY FROM BETTER UPPER FORCING AND MORE STABLE MID
LEVELS...EXPECT A SOMEWHAT DECAYING COMPLEX OF ELEVATED RAIN AND
EMBEDDED THUNDERSTORMS TO PUSH ACRS MAINLY NORTHERN 2/3'S OF THE
CWA FROM LATE EVENING ON.

MAIN SHOW OF STRONG CONVECTION NOW APPEARS TO BE SAT AFTERNOON AND
NIGHT. VIGOROUS VORT(ALTHOUGH NOT AS VIGOROUS AS FEEDBACK REVVED UP
MODELS SUGGEST) WILL PULL UP IN SOUTHERLY FLOW RIGHT OVER THE AREA...
FOR A STRONG BOUT OF CVA COMBINED WITH UPPER JET DYNAMICS. FEEL
INCREASING SOUTHERLY FLOW AT SFC SHOULD HELP PUSH DPTS CLOSE TO 60
BY LATE SAT AFTERNOON...WITH CAPES PROBABLY EXCEEDING 1K J/KG ACRS
THE SOUTHERN HALF OF THE CWA. THUS WITH DYNAMIC MID AND UPPER SYSTEM
COMBINED WITH SOME LLVL INSTABILITY AND JUICE...STAGE WILL BE SET FOR
POSSIBLE SVR THUNDERSTORM EVENT...AGAIN SAT AFTERNOON AND EVENING.
FCST SOUNDINGS SUGGEST GOOD CHANCE OF DAMAGING WINDS SAT EVENING...
BUT LARGE HAIL ALSO A GOOD BET. HWO ALREADY UPDATED AND SENT
COVERING THIS POSSIBILITY. SECOND ROUND OF STORMS POSSIBLE LATER SAT
NIGHT AND TOWARD SUNDAY MORNING WITH YET ANOTHER WAVE PUSHING UP OVER
THE AREA COMBINED WITH UPPER JET MAX DYNAMICS. WILL LEAN TOWARD
WARMER FWC HIGHS ON SAT WITH EXPECTED WARM-SECTORIZATION OF THE CWA.

.LONGER RANGE(SUN-THU)...LATEST UKMET AND ECMWF SUGGEST UPPER LOW TO
CUT OFF SUNDAY OVER SOUTHERN MN...WHILE MRF/EX GFS MAINTAINS OPEN
WAVE OVER WRAPPED UP SFC SYSTEM. WILL SIDE WITH UKMET AND EURO BLEND
WHICH ROTATES MID LEVEL COLD POOL AND VORT SPOKE AROUND UPPER FEATURE
OVER THE AREA FOR SHOWER/STORM CHANCE SUNDAY ESPECIALLY EARLY...
ALTHOUGH DRY SLOT TO EVENTUALLY BE A PLAYER FOR A DRY PERIOD AS WELL.
MORE OF A WRAP AROUND COOL RAIN PROCESS FOR MONDAY FOR CONTINUED
PRECIP THREAT. HIGHS MONDAY MAY BE LIMITED TO THE LOWER 50S. THEN
BLOCKING UPPER RIDGE PATTERN TO THEN BUILD OVER THE CENTRAL CONUS FOR
THE MIDDLE PART OF NEXT WEEK...BUT ANOTHER STRONG SFC HIGH DROPPING
OVER THE NORTHERN GRT LKS AND RESULTANT NORTHEAST FETCH ACRS THE
LOCAL CWA...WILL TEMPER ANY POTENTIAL TEMPERATURE MODERATION FOR TUE
AND WED. MAY STILL GO WITH MEX VALUES UPPER 50S-AROUND 60 FOR MUCH OF
CWA TUE AND WED WITH INSOLATION...BUT WILL GO COOLER ACRS THE
NORTHEAST. DEPENDING ON STRENGTH OF BLOCKING UPPER RIDGE OVER THE
UPPER MIDWEST...BUT NEXT PRECIP THREAT MAY BE DUE BY LATE THU.


.DVN...
IA...NONE.
IL...NONE.
MO...NONE.

$$

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