435
FXUS63 KTOP 091602
AFDTOP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1002 AM CST TUE FEB 9 2010
UPDATE
RAN A QUICK FORECAST UPDATE FOR ONGOING SNOW SHOWERS ACROSS TOPEKA
AND VICINITY. THIN LAYER OF STRATUS IS RIGHT IN THE -10 TO -20
BETTER DENDRITIC GROWTH LAYER...AND BACK SIDE OF STRONG UPPER
SYSTEM DRAGGING SOME ENERGY ACROSS THE AREA BEFORE IT MAKES ITS
WAY EAST. TWO THINGS IN CONCERT ARE PRODUCING GOOD SNOW SHOWERS.
EXPECT AN INCH OR LESS OF ACCUMULATION...HOWEVER WITH SUCH COLD
AMBIENT AIR AND ROAD TEMPERATURES...EXPECT SLICK SPOTS ON ROADWAYS
THIS MORNING ALONG AND EITHER SIDE OF INTERSTATE 70.
PREV DISCUSSION
/ISSUED 550 AM CST TUE FEB 9 2010/
UPDATE...
UPDATED FOR THE 12 UTC AVIATION.
DISCUSSION...
SEE THE PREVIOUS DISCUSSION BELOW.
AVIATION...
STRATUS CEILINGS OF 2,500 TO 3,500 FEET WILL GRADUALLY LOWER TO
1,200 TO 1,800 FEET THROUGH THE MID AND LATE MORNING HOURS AND
CONTINUE THROUGH THE DAY AS WRAP AROUND RESIDUAL MOISTURE ADVECTS
SOUTHWARD ACROSS THE TAFS SITES ON THE THE WEST SIDE OF THE
UPPER LOW MOVING SOUTHEAST ACROSS NORTHWEST MO. THERE MAY ALSO BE
OCCASIONAL FLURRIES THROUGH THE DAY AS WELL. CEILINGS MAY GO VFR THIS
EVENING BEFORE WEAK WAA CAUSES CEILINGS TO GO BACK TO BELOW MVFR
LEVELS LATE TONIGHT ACROSS THE TAF SITES.
GARGAN
PREV DISCUSSION... /ISSUED 320 AM CST TUE FEB 9 2010/
DISCUSSION...
FORECAST FOCUS THIS MORNING WILL BE ON SNOWFALL CHANCE TODAY...AND
TEMPERATURES THROUGH THE NEAR/MID TERM PERIOD.
TODAY...500MB LOW CENTERED NEAR WEST CENTRAL IOWA NEAR FORECAST
ISSUANCE TIME WILL SHIFT ESE-WARD. CLEAR SKIES OBSERVED EARLY THIS
MORNING WILL BE RE-INUNDATED WITH CLOUDS AS MOISTURE WRAPS AROUND
THE NW/W SIDE OF THE SYSTEM. 09/00Z RUNS OF THE NAM...GFS...AND
ECMWF EACH FEATURE ACCUMULATING PRECIP MAINLY PRIOR TO 18Z
TODAY...WITH STEEP LL LAPSE RATES AND MODEST UVVS THROUGH THE
SHALLOW SATURATED CLOUD LAYER THAT COINCIDES WITH THE DENDRITIC
GROWTH ZONE. BEST CHANCE FOR A DUSTING OF SNOW WILL BE IN THE
NORTHEASTERN PORTION OF THE CWA...WITH FLURRIES EXPECTED WEST AND
SOUTH. INSERTED SLIGHT CHANCE POPS GENERALLY NORTH AND EAST OF A
LAWRENCE TO MARYSVILLE LINE BEFORE 18Z...WITH GENERAL FLURRY MENTION
MAINLY NORTHEAST DURING THE AFTERNOON HOURS. NORTHWESTERLY
WINDS...GUSTY AT TIMES ON THE BACKSIDE OF THE LOW...SPELL COLD
ADVECTION THROUGH THE DAY. TEMPERATURES SOME 15 DEGREES COOLER THAN
CLIMATOLOGICAL AVERAGES ARE EXPECTED TODAY...WITH HIGHS IN THE
MID-20S.
TONIGHT AND WEDNESDAY...SFC RIDGE AXIS SHIFTS EASTWARD THROUGH THE
PLAINS STATES. WEAK RIDGING ALSO BUILDS INTO THE UPPER ATMOSPHERE.
STUBBORN STRATOCU MAY BE A BIT SLOW TO ERODE...BUT BELIEVE THE
IMPINGING DRY AIRMASS SHOULD BE ENOUGH TO SCOUR OUT THE LOW LEVEL
MOIST LAYER FROM NW TO SE THROUGH THE NIGHT. LOWERED LOWS TONIGHT
TO REFLECT EXPECTED CLEARING SKIES. ALSO LOWERED HIGHS A TOUCH
EAST WED AFTERNOON NEAR SFC RIDGE AXIS WITH LITTLE MIXING AS WIND
FIELD WILL BE AOB 10KTS FROM THE SFC THROUGH 800MB.
THURSDAY AND FRIDAY...LOCAL AREA LOOKS TO SIT BETWEEN TWO NORTHERN
STREAM AND A SOUTHERN STREAM SHORTWAVE TROUGH PASSING ESE-WARD
THROUGH THE MEAN NORTHWESTERLY FLOW REGIME. BEST MOISTURE RETURN AND
SOUTHERN STREAM SHORTWAVE ENERGY FOCUSES WELL SOUTH OF THE FORECAST
AREA. FIRST MINOR NORTHERN STREAM WAVE BRINGS LITTLE MORE THAN
INCREASE MID-CLOUDS. SECOND...MORE AMPLIFIED TROUGH SENDS A COLD
FRONT THROUGH THE PLAINS FRIDAY. PREFERRED THE SLOWER PROGRESSION
OF THE 500MB SHORTWAVE TROUGH AND COLD FRONT NOTED ON THE 09/00Z AND
09/00Z ECMWF AS OPPOSED TO THE FASTER...MORE AMPLIFIED OUTLIER
GFS...THEREFORE RAISED MAXIMUM TEMPERATURES A FEW DEGREES TO REFLECT
EXTENDED PERIOD OF SOUTHERLY FLOW/EARLY SUNSHINE AHEAD OF THE FROPA.
NO CHANGES MADE BEYOND FRIDAY.
LUNDE
TOP WATCHES/WARNINGS/ADVISORIES
NONE.
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