217
FXUS63 KLOT 071121
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
520 AM CST TUE DEC 7 2004
.DISCUSSION...
CURRENT SYSTEM WILL DEPART THE REGION LATER TODAY WITH PRECIP
ENDING FROM SW TO NE BY EARLY AFTERNOON...SOME LINGERING/SPOTTY
SHOWERS WILL BE POSSIBLE THROUGH THE AFTERNOON HOURS. HIGH TEMPS
FOR TODAY HAVE JUST ABOUT BEEN REACHED AT MOST LOCATIONS...
EXPECT TEMPS TO HOVER CLOSE TO CURRENT VALUES BEFORE A SLOW
DECREASE THIS AFTERNOON WITH THE PASSAGE OF THE SFC-H85 COLD
FRONT. PER BUFR SNDGS IT WILL BE RATHER BREEZY COME THIS
AFTERNOON AS THE DEPARTING CIRCULATION DEEPENS TO OUR EAST AND
THE PBL FLOW INCREASES BEHIND THE SFC-H85 FROPA. ON WED MID-LVL
RIDGING JUXTAPOSED WITH A THERMAL RIDGE WILL ALLOW FOR A RATHER
NICE DAY...MID-LVL CLOUDS LIKELY GIVEN WAA AND AVAILABLE RH.
LATE ON WED MARKS THE START OF WHAT IS STRONGLY ADVERTISED
BY NEARLY ALL THE OPERATIONAL MEDIUM RANGE MODELS AND THEIR
RELATED ENSEMBLE FAMILIES, TO BE A LARGE PATTERN SHIFT IN THE
NOAM MID/UPR FLOW. RISING HEIGHTS OVER THE WRN CONUS WILL ALLOW
FOR THE AMPLIFICATION OF WHAT WILL BE A HIGH AMPLITUDE ERN
NOAM TROUGH COME THIS WEEKEND. THE LEAD S/WV AND DEEPENING
LOW WILL DROP TO THE SOUTHEAST OUT OF CANADA PRAIRIE AND ACROSS
THE CWA LATE ON THR INTO FRI MORNING. FOR NOW LEFT THR DRY AS
TIMING A BIT UNCERTAIN COMPOUNDED WITH THE BEST FORCING REMAINING
NORTH OF THE CWA. AS THE DEVELOPING UPR LVL LOW TRANSITIONS SE OF
THE CWA, OUR WINDOW FOR PRECIP OPENS THR NIGHT INTO FRI. BOTH
THE ETA AND GFS' VARIES ATMO THICKNESSES INDICATE A
RATHER WARM COLUMN SUPPORTIVE OF LIQUID PRECIP WITH PERHAPS A
SMALL TIME PERIOD ON FRI FOR A MIX AT THE TAIL END OF THE
PRECIP WHEN DIABATIC EFFECTS IN CONJUNCTION WITH CAA ARE
MAXIMIZED.
AGREE WITH THE OVERNIGHT HPC MED-RANGE DISC THAT UNCERTAINTY
IS VERY LARGE REGARDING THE AMPLITUDE OF ERN NOAM TROUGH. FOR
TONIGHT AM FAVORING A DEEPER SOLUTION AS INDICATED BY THE EC AND
GEM H5 ENSEMBLE STD-DEV SOLUTIONS. THEREFORE WILL LEAVE INHERITED
PRECIP TIMING AND TYPES AS THERE ARE FOR SAT-MON BUT INCREASED
CLOUD COVER. WILL CAUTION THAT AM HIGHLY SUSPICIOUS THAT
TEMPS ARE TOO WARM FROM SUN INTO TUE AS THE REGION SHOULD BE
UNDER SWIFT NW FLOW, UPWIND OF THE TROUGH AXIS. I HAVE NUDGE HIGH
TEMPS DOWNWARD A FRAZ TO THAT OF THE HPC VALUES FOR SUN THRU TUE
TO SIGNAL A COLDER SOLUTION.
&&
.AVIATION DISCUSSION FOR 12Z TAFS:
SFC LOW HAS MOVED NORTHEAST OF STL NOW ENROUTE TO GYY AREA BEFORE
NOON TODAY...THEN OFF TO LAKE HURON BY DARK. WRAPAROUND RAIN TO THE
NORTH OF THIS LOW WILL CONTINUE THROUGH MOST OF MORNING...FINALLY
DRYING OUT BEHIND IT BY MID AFTERNOON. WINDS SHUD BACK TODAY TO THE
NORTH BY 1000 AM...THEN NW FOR THE AFTN. BUFKIT ONLY GIVING 25 KT
DOWNSLOPE TO SFC TODAY...SO AM BACKING OFF FROM NEAR 30 KTS. WINDS
CONTINUE BACKING THRU NIGHTFALL AND DIMINISHING INTENSITY AS LOW
PULLS AWAY TONIGHT. THUS HAVE MORE WEST WINDS LESS THAN 10 KNOTS BY
WEDNESDAY MRNG. CIGS HAVE BEEN UP AND DOWN...VFR TO LIFR AND BACK UP
AGAIN. THIS WILL CONTINUE UNTIL COLD FRONT MOVES THRU AND END PCPN
BY MIDDAY WITH SKIES CLEARING BY DAWN WEDNESDAY AS HIGH PRESSURE
TAKES HOLD OF THE REGION.
RLB
&&
.LOT...WATCHES/WARNINGS/ADVISORIES...
.IL...NONE
.IN...NONE
.LK MI...SCA ILLINOIS AND INDIANA NEARSHORE TODAY TONIGHT EARLY
WEDNESDAY
$$
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