[LeArc] Forecast Discussion : MLI@ 1/25/03 2:23:05 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 250835
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
230 AM CST SAT JAN 25 2003

NO SHORTAGE OF CONCERNS WITH CHANGEABLE PATTERN ENVELOPING REGION NEXT
SEVERAL DAYS. 

LATEST SURFACE ANALYSIS SHOWS MAIN FRONTAL ZONE EXTENDING FROM SOUTH 
CENTRAL MN INTO EXTREME NORTHERN NE. SECONDARY FRONT POSITIONED
ROUGHLY FROM LAKE SUPERIOR INTO THE ARROWHEAD OF MN. ARCTIC HIGH CENTERED 
OVER NORTHERN ALBERTA AND SASKATCHEWAN TO DIVE S/E THROUGH 
PLAINS NEXT 24 TO 36 HRS SENDING AREA TEMPORARILY BACK IN THE DEEP FREEZE. 
UA ANALYSIS SHOWS NORTHWEST FLOW IN MID LEVELS WITH VORT COMPLEX 
SHIFTING FROM NORTHERN ROCKIES INTO NORTHERN PLAINS COMBINING WITH
COLD ADVECTION TO WRING OUT -SN/--SN WITH VISIBILITIES MAINLY 2 TO 6 MILES.

CONCERNS NEAR TERM INCLUDE FRONTAL TIMING...ASSOCIATED SNOW CHCS AND
AMOUNT OF PRE-FRONTAL WARMUP...THEN EXTENT OF COOL DOWN TNGT
AND WINDS WITH BITTER COLD WIND CHILLS. BEYOND...CONCERNS ARE WITH EXTENT 
OF WARMUP MON-TUE AND PCPN CHCS.  

MODELS SHOWING SLIGHT TIMING DIFFS WITH FRONTAL PASSAGE...OVERALL EXPECT
PASSAGE DURING AFTN/EVE AS ARCTIC HIGH BUILDS SOUTH INTO PLAINS AND
VORT COMPLEX SHIFTS INTO MIDWEST IN NORTHWEST MID LEVEL FLOW.
TEMPS INITIAL CONCERN AND WITH SOME SUNSHINE TO START AND AMPLE MIXING
WITH SOUTHWEST WINDS AROUND 10-12 KTS ESP CENTRAL AND SOUTHERN
ZONES WILL SIDE TOWARD WARMER MET GUIDANCE. FRONTOGENETICAL FORCING 
IN CONJUNCTION WITH MOISTENING LOW AND MID LEVELS SUGGEST/S 
QUICK SHOT OF -SN/--SN ALONG AND BEHIND FRONT BEFORE STRENGTHENING TEMP
GRADIENT SHOVES ACTIVITY SOUTH OF CWA OVERNIGHT. ACCUMULATIONS
SHOULD BE LIMITED MAINLY TO DUSTING TO FEW TENTHS OF AN INCH DUE TO
SPEED OF FRONTAL ZONE AND NARROW WINDOW OF COALESCENCE 
OF FORCING AND SATURATION. ATTENTION THEN SHIFTS TO WINDS/WIND CHILLS
AND LOW TEMPS. GRADIENT LIKELY TO KEEP WINDS IN 10-20 MPH RANGE 
MOST OF THE NIGHT WITH HIGHER GUSTS POSSIBLE FOR A WHILE THIS EVENING.
SUBSIDENCE BEHIND DEPARTING VORT COMPLEX AND FRONT TO SCOUR OUT
MOST OF THE CLOUDS LEAVING CLEAR/PC SKIES EXCEPT IN THE S/E WHERE SKIES
MAY REMAIN MOSTLY CLOUDY. BRISK WINDS LIKELY TO SEND WIND CHILLS
CLOSE TO OR JUST INTO LOW END OF ADVISORY MAINLY NORTHERN 1/3 AS TEMPS
PLUNGE INTO THE SINGLE DIGITS. FOR NOW...WILL HIGHLIGHT 
WIND CHILLS IN ZONES AND LET DAY CREW RE-EVALUATE NEED FOR AN ADVISORY.

SUNDAY WILL SEE STRONG COLD ADVECTION AND BLUSTERY NORTHWEST WINDS MAKING
FOR 'SUPER' CHILL. TEMPS TO STRUGGLE INTO THE 10-15 DEG F RANGE
WITH WIND CHILLS STAYING BELOW ZERO MOST...IF NOT THE ENTIRE DAYTIME PERIOD.

SUNDAY NIGHT...SURFACE RIDGE AXIS OVERHEAD DURING FIRST HALF OF NIGHT
TO PROVIDE NEAR IDEAL RADIATIONAL COOLING SETUP.
MODELS WITH LAST ARCTIC INTRUSION WERE TYPICALLY TOO COLD WITH LACK OF DEEP
SNOWCOVER...ESPECIALLY THE MAV GUIDANCE. THUS...WILL FOLLOW MORE
WITH MET/FWC BLEND...STILL BELOW ZERO MOST LOCALES BEFORE RIDGE AXIS SHIFTS
EAST BY MON MORNING.

SOUTHERLY FLOW AND STRONG WARM ADVECTION TO COMMENCE ON MON SUPPORTING
CHC POPS. NEXT FEW SHIFTS MAY NEED TO BUMP POPS INTO LIKELY CAT
IF LLVL FORCING STILL AS ADVERTISED FROM 00Z RUNS. MODELS HAVE BACKED OFF SOME 
ON MAXES TO NO SURPRISE GIVEN USUAL BIAS OF TRYING TO LIFT OUT ARCTIC AIRMASS 
TOO QUICKLY...THEREFORE WON/T GO HOG WILD WITH WARMING GIVEN THIS AND 
EXPECTED PCPN. HOWEVER...MAV GUIDANCE LOOKS A BIT COOL WITH AMPLE MIXING...AND 
WILL STAY CLOSE TO PREVIOUS FORECAST. 

NEXT FRONT SLATED TO ARRIVE ON TUE. GOING TEMPS MAY BE A BIT OPTIMISTIC
IF AVN/GFS FRONTAL TIMING IS CLOSE. ALSO AVN/GFS AND MRF GENERATING 
SOME LIGHT PCPN...BUT WON/T MAKE ANY CHANGES ATTIM DUE TO UNCERTAINTY WITH
FRONTAL TIMING. 

COORD WITH LSX...THANX!

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

05