[LeArc] Forecast Discussion : MLI@ 3/10/03 2:35:18 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 102044
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
240 PM CST MON MAR 10 2003

WEAK VORT SHEARING DOWN THROUGH NORTHWEST FLOW AND ACRS IA THIS
AFTERNOON AND EVENING...IS KICKING UP AREA OF LIGHT SNOW AND
FLURRIES JUST NORTHWEST OF DSM ATTM. SHORT RANGE MODELS BRING THIS
FEATURE THROUGH THE LOCAL CWA DRY THIS EVENING...BUT OBVIOUSLY
ENOUGH POS OMEGAS...CVA...ISENTROPIC LIFT AND OTHER FORCING AND
SATURATION TO PRODUCE PRECIP. QUESTION IS IF ENOUGH DRY AIR IN PLACE
OVER EASTERN IA THAT WILL ERODE PRECIP AND PREVENT MUCH OF ANY SFC
ARRIVAL. LOOKING AT 290 K ISENTROPIC ANALYSIS...ETA MOST BULLISH ON
EXTENT OF ISENTROPIC LIFT AND LOWERING OF CONDENSATION PRESSURE
DEFICITS...BUT STILL PAINTS DRY PICTURE WITH MODEL QPF. AVN-GFS
WEAKER AND PARALLEL TO SFCS WITH LIFT...ALTHOUGH SUGGESTING ENOUGH
SATURATION FOR SOME LIGHT PRECIP. FEEL ENOUGH FORCING AND SATURATION
FOR AT LEAST LIGHT SNOW/FLURRY CHANCE ACRS NORTHERN 2/3'S OF THE CWA
THIS EVENING...ESPECIALLY LOOKING AT UPSTREAM PRECIP TRENDS ON
REGIONAL 88D LOOPS.

HIGHS TODAY HAVING TROUBLE MAKING IT TO PROJECTED LOWS FOR TONIGHT...
AND WILL UNDERCUT GUIDANCE SOME WITH LOWS IN UPPER SINGLE DIGITS...
TO THE LOW TO MID TEENS. LOWS WILL OCCUR THIS EVENING THROUGH
MIDNIGHT...BEFORE SOUTHERLY SFC FLOW WRAPPING AROUND DEPARTING
ANTICYCLONE CAUSES STEADY OR SLOW RISE TEMP PHENOMENON. FAR EAST
CENTRAL CWA AND WEST CENTRAL IL WILL BE LAST TO EXPERIENCE THIS TEMP
REBOUND EFFECT(CLOSER TO RIDGE AXIS THE LONGEST). WITH EXTENT OF
WAA ALOFT IN LOW TO MID LAYERS...WILL KEEP MOSTLY CLOUDY SKIES OVER
MOST OF THE CWA OVERNIGHT.

COMBINATION OF CONTINUING RETURN FLOW BEHIND DEPARTING SFC RIDGE AND
UP INTO NORTHERN STREAM WAVE PUSHING ACRS THE LK SUPERIOR
REGION...TO STRENGTHEN SOUTH-SOUTHWEST WINDS OVER THE AREA ON
TUE. THIS OF COURSE TO BRING WELCOME WARMING...BUT FEEL LINGERING
SNOW PACK STILL ENOUGH TO TEMPER POTENTIAL. WOULDN'T BE SURPRISED
IF MUCH OF CWA HAD TROUBLE GETTING OUT OF THE 30S...EXCEPT THE FAR
SOUTHERN CWA AND WEST CENTRAL IL(MACOMB AREA) WHERE LESS SNOW COVER
EXISTS...AND INCOMING SOUTHERLY FETCH OFF SNOW-LESS TERRAIN OVER MO
WILL HELP BOOST TEMPS. COOLER FWC HIGHS ACTUALLY MAY BE IN THE BALL
PARK...BUT MAY EVEN HAVE TO TEMPER/UNDERCUT FWC HIGHS FOR THE MID
PORTIONS OF THE CWA. WILL LET TEMPS BEAT ME ON THE HIGH SIDE
TOMORROW...IF THEY CAN.

AS FRONT TRAILING FROM NORTHERN STREAM SYSTEM SAGS ACRS THE CWA BY
MID TUE NIGHT...MAY BE ENOUGH LLVL CONVERGENCE AND MOISTURE RETURN
TO GENERATE LIGHT RAIN OR DRIZZLE ACRS THE SOUTHERN THIRD OF THE CWA
TUE EVENING. FOG MAY ALSO BE A FACTOR OVER MUCH OF THE CWA....WITH
LIGHT CONVERGING WINDS AND SNOWMELT MOISTURE NEAR THE SURFACE.

BIG DIFFERENCES IN MODEL SOLUTIONS ON WED WITH DEVELOPING ORIENTATION
OF WEST-TO-EAST FRONT. GFS AND UKMET MUCH STRONGER WITH RETURN FLOW
AND PUSHING FRONT BACK NORTH TO NORTHERN FRINGES OF THE CWA...
ALLOWING FOR MUCH WARMER SFC TEMPS. ETA IS STRONGER AND FURTHER
SOUTH WITH SFC HIGH DROPPING ACRS WI AND THE WESTERN GRT LKS...
KEEPING SFC FRONT AT BAY ACRS THE SOUTHERN CWA. THIS WOULD BRING
COOLER EAST-NORTHEAST FLOW FETCH OFF LK MI...WITH HIGH TEMPS MUCH
COOLER THAN GUIDANCE. WITH THE WAY THINGS HAVE BEEN SETTING UP
SOUTH THIS WINTER...WILL LEAN TOWARD ETA SOLUTION. MAIN VORT/WAVE
OF THE WEEK STILL LOOKS TO ROLL DOWN ACRS THE UPPER MIDWEST AHEAD OF
INCOMING UPPER RIDGE FOR PRECIP THREAT WED NIGHT. MAY GO WITH ALL
RAIN WORDING FOR NOW...BUT CRITICAL THICKNESSES SUGGEST THERE COULD
BE SOME SNOW OR MIX ACRS THE NORTH.

.LONGER RANGE(THU-MON)...WAVE WILL DEPART ON THU...BUT WRAP AROUND
RAIN(POSSIBLE RAIN-SNOW NORTH) SHOULD STILL AFFECT THE CWA IN THE
MORNING. BACKDOOR TYPE SFC HIGH AND NORTHEAST FLOW OFF LK MI WILL
THEN LOOK TO SLIDE SOUTH-SOUTHWEST OVER THE AREA AND MAKE FOR A
COOLER THAN GUIDANCE DAY. THEN...BY NOW WELL ADVERTISED RETURN FLOW
AT SFC AND APPROACHING BROAD UPPER RIDGE TO BRING VIGOROUS WARM UP
INTO THE WEEKEND. SAT COULD BE WARMEST OF ALL WITH MID 60S.
APPROPRIATE MIXING WITH INSOLATION AND A 70 NOT OUT OF THE QUESTION.
PACIFIC ENERGY WILL PROPAGATE ACRS THE CONUS AND TRY AND BREAK
DOWN STAUNCH RIDGE IN PLACE ACRS THE PLAINS AND WESTERN GRT LKS....
AS WELL AS RIDGE-RIDERS FROM THE NORTH. MAY BE ENOUGH UPPER
SUPPORT FOR SHOWER THREAT ON SUNDAY. MRF SUGGESTS LARGE CANADIAN HIGH
TO BACKDOOR ITS WAY OVER THE WESTERN GRT LKS AND THE LOCAL AREA AGAIN
ON MONDAY FOR COOL DOWN(NORTHEAST FETCH OFF LK MI).


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

$$

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