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000
FXUS63 KTOP 100921
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
321 AM CST WED FEB 10 2010

.DISCUSSION...

FORECAST FOCUS WILL BE ON POTENTIAL FOR LIGHT FREEZING DRIZZLE
TONIGHT THROUGH THURSDAY MORNING...PRECIPITATION CHANCE THIS
WEEKEND...AND TEMPERATURES FOR THE NEXT SEVERAL DAYS. NO CHANGES
WERE MADE BEYOND SATURDAY.

TODAY...ELONGATED AXIS OF HIGH PRESSURE WILL PREVAIL ACROSS THE
CENTRAL CONUS TODAY. EARLY MORNING STRATOCU NOTED ON 11-3.9 MICRON
SATELLITE IMAGERY OVER THE EASTERN PORTION OF THE FORECAST AREA WILL
ERODE THROUGH DAYBREAK. WILL SEE A GOOD BIT OF SUNSHINE THROUGH THE
MORNING AND EARLY AFTERNOON. WEAK WINDFIELD SPELLS POOR MIXING...BUT
MENTIONED SUNSHINE AND MINIMAL SNOWPACK WILL HELP TEMPS RISE INTO
THE MID TO UPPER 20S.

TONIGHT THROUGH THURSDAY...SFC RIDGE BEGINS TO SHIFT EASTWARD AS
500MB CLOSED LOW PROGRESSES THROUGH THE SW CONUS AND NORTHERN
MEXICO. LOW LEVEL MOISTURE TRANSPORT AND WARM ADVECTION VIA BACKING
SOUTHWESTERLY WINDS IN THE 925:850MB LAYER AHEAD OF THE LOW PICK UP
AFTER 06Z THURS. THIS LAYER SATURATES AFTER 09Z...AND PERSISTENT
WEAK LIFT THROUGH AROUND 15Z WITHIN THE LAYER INFERS A PERIOD FOR
PRECIP. DENDRITIC GROWTH ZONE DOES NOT SATURATE DURING THIS TIME
PERIOD. WITHOUT THE INTRODUCTION OF ICE CRYSTALS INTO THE CLOUD
LAYER...BELIEVE THE PRIMARY PRECIPITATION TYPE WILL BE DRIZZLE.
NOTABLY...SFC TEMPS WILL BE 10F TO 15F DEGREES BELOW FREEZING
OVERNIGHT...THEREFORE INTRODUCED PATCHY FREEZING DRIZZLE AND PATCHY
FREEZING FOG WEST THROUGH MID-MORNING THURS. A BIT DRIER AIR HANGS
IN PLACE FURTHER EAST.

FRIDAY AND SATURDAY...SEVERAL SHORTWAVE TROUGHS ZIP THROUGH THE MEAN
NORTHWESTERLY FLOW AT 500MB. FIRST SHORTWAVE ARRIVES EARLY FRIDAY
MORNING...AND DRAGS A WEAK COLD FRONT THROUGH BY MID-DAY. LITTLE IN
THE WAY OF MID-LEVEL MOISTURE TO WORK WITH...THEREFORE MAINTAINED
DRY FORECAST. WIND SHIFT BACK TO THE NORTHWEST WILL BE THE MOST
EVIDENT FEATURE ASSOCIATED WITH THE FROPA. STRONGER...MORE AMPLIFIED
SHORTWAVE DROPS THROUGH THE NORTHERN PLAINS AND INTO THE
MID-MISSISSIPPI RIVER VALLEY REGION BEGINNING SATURDAY. THIS
DEEPENING LOW DRAGS ANOTHER COLD AIRMASS SOUTHWARD//SEE NOTE IN NEXT
PARAGRAPH//MARKING THIS LATE WEEK FROPA AS THE ONE TO IMPACT
TEMPERATURES. WITH PREFERRED LATER/MID-AFTERNOON/ARRIVAL OF THE
FRONT...DID LEAVE MAXES TOWARD THE WARMER EDGE OF THE GUIDANCE
ENVELOPE. BRUNT OF PRECIPITATION FOCUSES NEARER STRONGEST PV
ADVECTION AND DEEPER MOISTURE...MAINLY ACROSS IOWA AND MISSOURI.
WITH THE EASTERN HALF OF THE CWA ON THE FRINGE OF THE BETTER
FORCING/MOISTURE...OPTED TO ADD SLIGHT CHANCE POPS 12Z SAT TO 00Z
SUN. PRECIP TYPE MAY BE MORE OF A RAIN/SNOW MIX TOWARD AFTERNOON
PENDING ARRIVAL OF THE COLD FRONT...BUT WILL LEAVE ALL SNOW MENTION
THROUGH THE PERIOD FOR THE SAKE OF SIMPLICITY AND SOME QUESTION AS
TO FROPA TIMING.

THEREAFTER...WILL WATCH TEMPS SUNDAY AS COLD AIRMASS SEEPS INTO THE
REGION BEHIND ANOTHER COLD FRONT LATE SATURDAY NIGHT INTO SUNDAY.
PAST FEW RUNS OF LONG RANGE MODEL SOLUTIONS HAVE BEEN FAIRLY
CONSISTENT DEPICTING THIS COOL DOWN. GOING HIGHS BOTH SUNDAY AND
MONDAY MAY BE A BIT TOO WARM FOR EXPECTED COLD AIR INUNDATION.

KONOP

&&

.AVIATION...

BKN AREA OF CLOUDS HAS BEEN SLOW TO DISSIPATE THIS EVENING. THE
BACK EDGE IS SLOWLY MAKING ITS WAY TOWARD TOP/FOE AND SKIES SHOULD
BE SKC BY DAWN.

VFR IS EXPECTED AFTER THE CLOUDS CLEAR OVERNIGHT.

SALLY

&&

.TOP WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$