[LeArc] Forecast Discussion : MLI@ 10/15/02 2:46:26 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 151954
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
250 PM CDT TUE OCT 15 2002

FIRST CHALLENGE OF FORECAST IS HOW COLD TONIGHT AND NEED OF ANY
FREEZE/ FROST HEADLINES IN REMAINING COUNTIES THAT HAVEN'T DONE SO
YET(GENERALLY SOUTHEAST THIRD OF THE CWA). VIS LOOP INDICATING CI AND
SOME AC STREAKING SOUTHEAST TOWARD EAST IA OUT OF THE DAKOTAS AND
SOUTHWEST MN ON NOSE OF 90 KT LEAD JET MAX AND VORT FROM CANADIAN
ROCKIES. THUS SOME CLOUDS AND THE FACT THAT THE RIDGE CENTER WILL
LOOK TO SETTLE JUST TO THE WEST OF THE CWA ENOUGH TO ALLOW LINGERING
GRADIENT TO SQUEEZE AT LEAST A LIGHT NORTH BREEZE WELL INTO THE
OVERNIGHT PERIOD...SHOULD PREVENT A COMPLETE BOTTOM OUT OF TEMPS.
STILL EXPECT SOME DECOUPLING OVER THE FAR WESTERN CWA FOR LIGHT WIND
REGIME...AND TEMPS MAY DIP INTO THE UPPER 20S FROM IOW TO WEST OF
DBQ...BUT THESE AREAS ALREADY HAVE MET FROST/FREEZE CRITERIA. EXPECT
AREA OF HEADLINE CONCERN TO MAINLY RANGE IN LOW TO MID 30S...WITH
PATCHY/AREAS OF FROST STILL POSSIBLE AND WILL MENTION. MAV LOWS LOOK
GOOD AND WILL NOT DEVIATE MUCH FROM...EXCEPT ACRS THE NORTHWEST WHERE
UPPER 20S WILL BE ADVERTISED.

WEDNESDAY WILL BEGIN PERIOD WERE ADDITIONAL JET MAX ENERGY WILL
PLUNGE OUT OF THE NORTHWEST TERRITORY AND DEEPEN THE TROUGH OVER THE
CENTRAL CONUS...WITH CRESCENDO EFFECT OCCURRING AROUND 12Z THU.
ADDITIONAL VORT PIECES WILL SHUTTLE DOWN THROUGH THIS FLOW...WITH
MAIN PIECE STILL LOOKING TO DROP DOWN ACRS THE UPPER MIDWEST/IA ON
THU MORNING. AVN STILL THE MOST VIGOROUS IN VORT STRENGTH...WITH ETA
SOMEWHAT WEAKER. SHORT RANGE MODEL GENERAL ENSEMBLE STILL DEVELOPS
CLOSED LOW SFC REFLECTION...BUT APPEARS FARTHER NORTH THIS RUN WITH
FEATURE TAKING SHAPE AROUND 12Z THU IN VCNTY OF MN/IA/WI TRI-STATE
REGION. SFC LOW THEN GENERALLY PROGGED TO THEN TRACK EAST-SOUTHEAST
ALONG WI/IL BORDER THROUGH EARLY THU AFTERNOON. DEFINITELY A DYNAMIC
SYSTEM WITH LEFT EXIT DIFFLUENT EFFECT OFF 115-120 KT H3 JET MAX
ADDING TO THE UVV PUNCH EARLY THU MORNING OVER THE AREA...BUT BEST
LOWER LEVEL CONVERGENCE FOR MORE PRECIP GENERATION LOOKS NOW TO
APPEAR JUST TO THE NORTH ACRS SOUTHEAST MN/NORTHEAST IA AND SOUTHERN
WI. REST OF CWA NOT OUT OF THE WOODS THOUGH(ESPECIALLY NORTHERN
THIRD)...AND STILL WARRANT AT LEAST 50 CHANCE POPS...IF NOT LIKELYS.
DEEP MOISTURE WILL BE LACKING WITH THIS SYSTEM THOUGH...AND PRECIP
AMOUNTS SHOULD BE ON LIGHT END. SATURATION PROCESS WILL ALSO EAT INTO
PRECIP AMOUNT POTENTIAL. AS FOR THE HEADACHE OF PRECIP TYPE...LIGHT
PRECIP IN FORM OF RAIN MAY INITIALLY SPREAD EAST ACRS THE WESTERN CWA
LATE WED NIGHT...WITH EVAPORATIVE COOLING ALLOWING BOUNDARY LAYER TO
REACH THERMAL PARAMETERS LOW ENOUGH FOR RAIN SNOW MIX OR ALL SNOW BY
12Z THU...MAINLY NORTH OF THE I-80 CORRIDOR. ALL OTHER SNOW
PARAMETERS STILL SUPPORT ALL WET SNOW ACRS THE NORTHERN THIRD UNTIL
LATE MORNING...WHEN MIX BACK TO LIQUID PHASE CHANGE OCCURS BEFORE
PRECIP ENDS. LOOKING AT LLVL CONVERGENT AND FORCING...AS WELL AS
SOUTHERN EXTENT OF BETTER MID LEVEL POS OMEGAS...POTENTIAL OF AN INCH
OR TWO OF WET SNOW ON GRASSY AND ELEVATED SFCS ALONG AND NORTH OF A
CID...TO SQI LINE BY 18Z THU. SHOULD BE INTERESTING AND WILL TRY AND
ZERO IN ON LATER ZONE PACKAGES AND JUST ADVERTISE CHANCE IN ZONES FOR
NOW.

.LONGER RANGE(FRI-TUE)...WILL TAKE LATEST ECMWF/UKMET COMPROMISE...
WHICH ARE MORE SIMILAR IN WITH THEIR SOLUTIONS THROUGH THE EXTENDED
PERIOD. THESE MODELS ARE QUICKER WITH FROPA ASSOCIATED WITH NEXT
SIGNIFICANT VORT DROPPING THROUGH THE SOUTHERN RING OF HUDSON BAY
POLAR VORTEX FRI NIGHT INTO SAT MORNING. PRE-FRONTAL WAA SHOULD BUMP
TEMPS ABOVE LATEST GUIDANCE VALUES BY LATE FRI AFTERNOON...EVEN AFTER
COLD START TO DAY. WITH SFC RIDGE ACRS THE WEST GULF INHIBITING
MOISTURE RETURN...EXPECT FROPA TO BE DRY ACRS THE LOCAL AREA. AGAIN
LIKE UKMET AND EURO'S STRONGER AND FURTHER SOUTH SOLUTION OF INCOMING
SFC RIDGE SHUNTING BAROCLINIC RIBBON FURTHER SOUTH. COOLER FMR
HIGHS(LOW TO MID 50S) ACTUALLY LOOK IN LINE FOR SAT IN CAA REGIME BUT
WITH SOME INSOLATION. MRF SLOWER/WEAKER WITH INCOMING HIGH AND THUS
MUCH FURTHER NORTH WITH BAROCLINIC HIGHWAY...ALLOWING SOUTHERN STREAM
IMPULSE TO OVER-RIDE PRECIP OVER THE CWA BY SUNDAY. WILL AGAIN GO
WITH STRONGER AND FURTHER SOUTH HIGH SOLUTION FOR FAIR...DRY AND
SEASONABLY COOL END TO WEEKEND. EARLY NEXT WEEK UNCERTAIN WITH ALL
MODELS DIVERGING. CWA MAY BE DUE FOR SOME PRECIP...INDUCED BY IMPULSE
IN FIRMLY ENTRENCHED STEEP CYCLONIC FLOW...BY MONDAY BUT FEEL CHANCE
NOT ABOVE CLIMO AND WILL KEEP DRY FOR NOW.


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

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