[LeArc] Forecast Discussion : MLI@ 9/15/02 2:54:03 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 150800 CCA
AFDMLI

AREA FORECAST DISCUSSION...CORRECTED SENTENCE SPACING TYPO...
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
258 AM CDT SUN SEP 15 2002

POST FRONTAL CLEAR OUT TIMING AND EXTENT OF CAA AND ITS AFFECT ON
HIGH AND LOW TEMPS OVER NEXT 24-36 HRS MAIN CHALLENGE THIS MORNING.

MAIN NEAR TERM CHALLENGE IS CLEARING TREND OF POST-FRONTAL STRATUS
ACRS SOUTHEAST HALF OF THE CWA THIS MORNING. LOOKING AT IR LOOP AND
INCOMING SUBSIDENCE STREAK TRENDS ON WATER VAPOR IMAGERY...
EXTRAPOLATION WOULD CLEAR MOST OF EAST AND SOUTHEAST CWA BY MID
MORNING. BUT...LATEST SHORT RANGE MODELS ALL SIMILARLY PROG HIGHER
1000-H85 LMRH'S TO HANG UP FROM JUST SOUTHWEST OF KAHOKA MO...TO
STERLING THROUGH AT LEAST 18Z. THIS PROBABLY RESULT OF LINGERING
EFFECT OF SFC WAVE ON FRONT PUSHING UP OH RVR VALLEY THIS MORNING.
BUT...EXTENT OF INCOMING SUBSIDENCE AND DEEP LAYER DRYING MAY MAKE
ACTUAL CLEARING ACRS THE EAST AND SOUTH OCCUR BY LATE MORNING...THUS
THE "IN-BETWEEN CARD MAY BE THE WAY TO GO. DRY AIR MIXING FROM ALOFT
AFTER SUNRISE SHOULD ALSO HELP EAT AT BACK EDGE OF EXITING CLOUD
DECK. WILL WATCH TRENDS OF LIGHT RAIN SKIRTING NORTHEAST ACRS THE
MACOMB AREA TOWARD ISSUANCE TIME...BUT AS OF NOW FEEL THERE WILL BE
NO NEED TO MENTION OR WALK THIS ACTIVITY OUT WITH TODAY'S ZONES.
SHORT WAVE TROUGH AND VORT PASSAGE TO EAST OF CWA BY MID MORNING ALSO
TO LEAD TO CLEARING TREND ACRS EAST.

REST OF TODAY MAINLY TO BE MOSTLY SUNNY...AS EVEN WITH STEEP 1000-H85
LAPSE RATES...INCOMING DRY AIR AND LACK OF SFC MOISTURE WILL PROHIBIT
DEVELOPING CU FIELD TO BE ENOUGH FOR PARTLY CLOUDY WORDING. AS FOR
THE EXTENT OF NORTH-TO-NORTHEAST SFC WINDS TODAY...IN-BUILDING
PRESSURE GRADIENT ON LEE SIDE OF HIGH...CAA REGIME AND LINGERING
CYCLONIC FLOW ALOFT WOULD NORMALLY SUPPORT BREEZY CONDITIONS. BUT
MODELS STILL PROG LLVL WINDS THAT WOULD BE MIXED DOWN TO DECREASE TO
AROUND 10 KTS BY 18Z. PROFILERS AND 88D VAD SHOW 25 KT NORTHERLY FLOW
ATTM AT 3-4K FT...WHICH IF THIS WAS MID MORNING THERE WOULD BE BREEZY
CONDITIONS. BUT AGAIN THIS LLVL FLOW PROGGED TO SLACKEN BY LATE
MORNING/MIDDAY...BUT FEEL IT WILL DECREASE SLOWER THEN MODELS
SUGGEST. WOULD EXPECT A MID MORNING SFC WIND SURGE UP TO 20 MPH WITH
FIRST MIX-OUT IN SUNNY AREAS ACRS THE NORTHWEST CWA...BUT THE WIND
SHOULD GRADUALLY DECREASE AS AFTERNOON PROGRESSES. AS FOR HIGHS
TODAY...AREAS THAT EXPERIENCE FULLER DAY OF INSOLATION AND MIXING
(GENERALLY ACRS THE WEST) COULD REACH THE MID 70S...WHILE THE FAR
EAST MAY HAVE TROUBLE REACHING 70.

AS SFC RIDGE CENTER SETTLES OVER THE CWA BY LATE TONIGHT...CLEAR SKY
AND CALM WIND TO ALLOW DRY AND COOLER AIRMASS TO HAVE FULL EFFECT ON
OVERNIGHT LOWS. GUIDANCE TEMPERATURES LOOK TOO WARM FOR MONDAY
MORNING AND WILL SIDE WITH ONGOING PACKAGE LOWS WHICH LOOK TO
CORRECTLY UNDERCUT THESE VALUES. BACKING LLVL FLOW TO ALLOW SOME
THERMAL RECOVERY ON MONDAY...AND WITH FULL SUNSHINE EXPECT HIGHS TO
CLIMB INTO THE MID TO UPPER 70S AS SFC RIDGE CENTER MOVES TO SOUTHERN
TIP OF LK MI.


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

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