FXUS63 KTOP 011220
AFDTOP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
620 AM CST TUE DEC 1 2009
.UPDATE...
UPDATED FOR 12 UTC TAFS.
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.DISCUSSION...
SEE PREVIOUS DISCUSSION.
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.AVIATION...
CHANGE IN WINDS IN THE LOWEST 1500 FT AGL STILL INDICATES SOME
POTENTIAL FOR LLWS THIS MORNING...SO HAVE CONTINUED IT IN TAFS
UNTIL 15Z. DECENT PRESSURE GRADIENT DURING THE DAY WILL KEEP
SOUTHERLY WINDS UP IN THE 15 KT RANGE. COLD FRONT APPROACHING THIS
EVENING SHOULD PASS MHK ABOUT 03Z AND TOP AND FOE ABOUT 05Z.
INITIAL CLOUDS WITH COLD FRONT WILL BE CIRRUS...BUT COULD GET A
STRATOCUMULUS CIG WELL AFTER MIDNIGHT.
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.PREV DISCUSSION... /ISSUED 327 AM CST TUE DEC 1 2009/
DISCUSSION...
THE 7Z WATER VAPOR SATELLITE IMAGERY ALONG WITH THE 00Z UPPER AIR
MAPS SHOWED AN INTENSE UPPER LEVEL TROUGH DIGGING SOUTHEAST ACROSS
THE PACIFIC NORTHWEST INTO THE GREAT BASIN REGION. A SOUTHERN STREAM
UPPER LOW WAS LOCATE ACROSS NORTHERN MEXICO JUST SOUTH OF THE AZ AND
NM BORDER.
THE 7Z SURFACE MAP SHOWED A LEE SFC TROUGH EXTENDING FROM WESTERN
ND...SOUTH-SOUTHWEST ACROSS EASTERN CO. A SFC COLD FRONT WAS PUSHING
SOUTHEAST ACROSS EASTERN AND SOUTHERN MT.
TODAY AND TONIGHT...THE INTENSE UPPER LEVEL TROUGH OVER THE PACIFIC
NORTHWEST AND GREAT BASIN WILL DIG SOUTHEAST ACROSS THE NORTHERN AND
CENTRAL HIGH PLAINS. THE RESULTING STRONG LOW-LEVEL CAA ACROSS THE
NORTHERN AND CENTRAL HIGH PLAINS WILL CAUSE A COLD FRONT TO PUSH
SOUTHEAST THROUGH THE DAY INTO SOUTHEAST NE AND WESTERN KS BY LATE
AFTERNOON. THE FRONT WILL MOVE SOUTHEAST ACROSS THE CWA THIS
EVENING. SOUTHWESTERLY LOW LEVEL WINDS AHEAD OF THE FRONT WILL HELP
TO WARM HIGHS TODAY INTO THE UPPER 50S TO AROUND 60 DEGREES ACROSS
THE CWA. HIGH CLOUDINESS WILL GRADUALLY INCREASE THROUGH THE
AFTERNOON HOURS AS THE UPPER LEVEL TROUGH DIGS SOUTHEAST INTO THE
NORTHERN AND CENTRAL HIGH PLAINS. THE UPPER TROUGH DIGGING INTO THE
NORTHERN AND CENTRAL HIGH PLAINS WILL ACT AS AN UPSTREAM KICKER AND
KICK THE SOUTHERN STREAM UPPER LOW OVER NORTHERN MEXICO NORTHEAST
INTO CENTRAL TX. THE GFS MODEL SHOWS STRONG ENOUGH ISENTROPIC LIFT
DEVELOPING BEHIND THE COLD FRONT FOR A MIX OF LIGHT RAIN AND SNOW TO
DEVELOP ACROSS THE SOUTHEAST COUNTIES OF THE CWA...GENERALLY
SOUTHEAST OF THE KS TURNPIKE AFTER MIDNIGHT. THE NAM MODEL FORECAST
A DRIER BOUNDARY LAYER AND SHOWS NO POST FRONTAL PRECIP DEVELOPING
ACROSS THE SOUTHEAST COUNTIES DURING THE NIGHT.
WEDNESDAY AND WEDNESDAY NIGHT...BOTH THE NAM AND GFS ARE PROGRESSIVE
KICKING THE UPPER LOW OVER NORTH CENTRAL TX NORTHEAST ACROSS AR INTO
THE CENTRAL OH VALLEY. THE UPPER TROUGH OVER THE NORTHERN AND
CENTRAL HIGH PLAINS WILL AMPLIFY AS IT DIGS SOUTHEAST ACROSS THE
EASTERN PLAINS AND MIDWEST. LOW-LEVEL CAA ACROSS THE THE CENTRAL AND
SOUTHERN HIGH PLAINS WILL ADVECT A MUCH COLDER AND DRIER AIRMASS
SOUTHEAST ACROSS THE CWA. HIGHS WEDNESDAY WILL STRUGGLE INTO THE
UPPER 30S ACROSS THE ENTIRE CWA AND NORTHERLY WINDS OF 15 TO 25 MPH
WITH GUSTS TO 30 MPH WILL CREATE WIND CHILL TEMPERATURES IN THE 20S.
THE 12Z EC MODEL IS A BIT SLOWER KICKING THE UPPER LOW OVER NORTHERN
MEXICO NORTHEAST ACROSS NORTH CENTRAL TX INTO AR. THE EC SOLUTIONS
SHOWS THE NORTHERN EDGE OF LIGHT SNOW...ASSOCIATED WITH THE UPPER
LOW MOVING NORTHEAST INTO AR... MOVING NORTHEAST ACROSS THE EXTREME
SOUTHEAST COUNTIES OF THE CWA ON WEDNESDAY...GENERALLY SOUTHEAST OF
I-35. THE EC SHOWS THE HEAVIER PRECIP REMAINING WELL SOUTH OF THE
CWA ACROSS OK...AR AND SOUTHERN MO ON WEDNESDAY. I KEPT A SLIGHT
CHANCE FOR RAIN AND SNOW ACROSS THE SOUTHEAST COUNTIES ON WEDNESDAY
IN CASE THE SLOWER AND SLIGHTLY NORTHERN TRACK OF THE EC MODEL
VERIFIES. ATTM...THERE WILL BE NO SNOW ACCUMULATIONS ACROSS THE
SOUTHEAST COUNTIES OF THE CWA.
THURSDAY AND THURSDAY NIGHT...ANOTHER 5H TROUGH WILL DIG SOUTHWARD
FROM WEST CENTRAL CANADA ON THE BACK SIDE OF THE STRONGER UPPER LOW
ACROSS THE MIDWEST. THERE MAY BE ENOUGH MID LEVEL MOISTURE ALONG
WITH THE ASCENT AHEAD OF THE 5H TROUGH AXIS FOR SOME SNOW FLURRIES
ACROSS THE CWA WEDNESDAY INTO WEDNESDAY EVENING. FORECAST SOUNDINGS
LOOK TOO DRY IN THE LOWER LEVELS OF THE ATMOSPHERE FOR ANY
MEASURABLE SNOWFALL. A SECONDARY SURGE OF COLD AIR WILL ADVECT
SOUTHEAST ACROSS THE CWA. HIGHS ON THURSDAY WILL STRUGGLE TO REACH
THE MID 30S...WITH SOME AREAS ACROSS NORTH CENTRAL AND NORTHEAST KS
NOT REACHING FREEZING. NORTHWEST WINDS WILL CONTINUE TO BE BRISK
MAKING IT FEEL EVEN COLDER. IF SKIES CLEAR THURSDAY NIGHT AND WINDS
DIMINISH...OVERNIGHT LOWS WILL DROP INTO THE LOWER TO MID TEENS.
FRIDAY THROUGH MONDAY...A BROAD UPPER LEVEL TROUGH WILL CONTINUE
ACROSS THE NORTH CENTRAL AND NORTHEAST CONUS. THIS WILL KEEP EASTERN
KS IN NORTHWEST FLOW ALOFT. THE GFS MODEL LOOKS DRIER THROUGH THE
PERIOD WHILE THE EC MODEL DIGS A 5H TROUGH ONSHORE ACROSS THE
PACIFIC NORTHWEST AND INTO THE CENTRAL PLAINS SUNDAY AND MONDAY
MORNING. THE EC THERMAL PROFILE WOULD SUPPORT SNOW. IF THE EC WERE
TO VERIFY MUCH OF THE CWA COULD SEE 1 TO 3 INCHES OF SNOW. ATTM...I
LEANED MORE TOWARDS THE GFS MODEL SOLUTION...KEEPING A DRY EXTENDED
FORECAST. IT WILL CONTINUE TO BE COOL WITH HIGHS THE MID 30S TO
LOWER 40S. OVERNIGHT LOWS WILL BE IN THE UPPER TEENS TO MID 20S.
GARGAN
&&
.TOP WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
