FXUS63 KTOP 260524
AFDTOP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1124 PM CST FRI DEC 25 2009
.UPDATE...
UPDATED FOR 06Z AVIATION.
&&
.AVIATION...
EXPECT ANOTHER BAND OF SNOW TO MOVE THROUGH ASSOCIATED WITH STRONG
SHORTWAVE TROF ALOFT MOVING THROUGH THE UPPER LOW. LEFT TEMPO
GROUP TO ACCOUNT FOR THIS...OTHERWISE EXPECT A SLOW DECREASE IN
WIND SPEEDS WITH LIGHT SNOW CONTINUING THROUGH THE DAY TOMORROW.
TOOK OUT BLSN IN THE MORNING AS SPEEDS DECREASE. STILL EXPECT CIGS
1500-2000FT AGL THROUGH THE TAF PERIOD. 67
&&
.PREV DISCUSSION... /ISSUED 950 PM CST FRI DEC 25 2009/
UPDATE...
WENT AHEAD AND EXPANDED THE WINTER WEATHER ADVISORY FOR SNOW AND
BLOWING SNOW TO INCLUDE ALL OF THE CWA THROUGH 6AM INSTEAD OF
DROPPING THE SOUTHERN HALF AT MIDNIGHT. EXPECT ANOTHER BAND OF
SNOW TO MOVE THROUGH AFTER MIDNIGHT...AND WINDS SHOULD TAKE A
SLIGHT TURN DOWN AFTER ABOUT 09Z. IN LIGHT OF LITTLE CHANGE
BETWEEN NOW AND 6AM...WITH FALLING AND DRIFTING SNOW STILL
CREATING TREACHEROUS TRAVEL CONDITIONS PARTICULARLY IN RURAL
AREAS...HAVE KEPT ADVISORY WHOLE AREA UNTIL 6AM. 67
&&
.DISCUSSION...
A BROAD UPPER LEVEL TROUGH WILL CONTINUE ACROSS THE CENTRAL PLAINS
TONIGHT AND GRADUALLY SHIFT NORTHEAST INTO THE MIDWEST SATURDAY
AFTERNOON. THE UPPER LOW THAT GAVE US THE BLIZZARD CONDITIONS LAST
NIGHT WAS LOCATED ACROSS NORTHERN IA. THIS UPPER LOW WAS FILLING BUT
IS FORECASTED TO ADVECT SOUTHWEST ACROSS EASTERN NE INTO THE BASE OF
THE LONGER WAVE LENGTH UPPER LEVEL TROUGH. MY THOUGHTS ARE THAT
THERE IS MORE MOISTURE AND LIFT ASSOCIATED WITH THIS UPPER LOW THAN
WHAT THE MODELS SHOW. WE WILL PROBABLY SEE MODERATE SNOW BANDS
CONTINUE TO DEVELOP AS THE WEAK TROWAL SHIFTS BACK SOUTHWEST ACROSS
NORTHEAST KS TONIGHT. TOTAL SNOW ACCUMULATIONS ALONG THE NE BORDER
WILL PROBABLY BE AROUND 3 INCHES WITH 1 TO 2 INCHES ACROSS THE
CENTRAL AND SOUTHERN CWA. THE WINDS WILL CONTINUE TO REMAIN IN THE
20 TO 30 MPH RANGE WITH GUSTS TO 40 MPH THROUGH THE EVENING
HOURS...SO CONSIDERABLE BLOWING AND DRIFTING OF THE SNOW WILL
CONTINUE THROUGH THE EVENING HOURS. I EXTENDED THE WINTER WEATHER
ADVISORY UNTIL 6Z ALONG AND SOUTH OF I-70 FOR 1 TO 2 INCHES OF
SNOW...AND CONTINUED BLOWING AND DRIFTING OF SNOW. THE COUNTIES
NORTH OF I-70 I EXTENDED THE WINTER WEATHER ADVISORY FOR SNOW AND
BLOWING SNOW THROUGH 12Z SAT. NORTH OF INTERSTATE 70 EXPECT 2 TO 3
INCHES WITH SOME LOCALLY HIGHER AMOUNTS ACROSS OUR NORTHEAST
COUNTIES ALONG THE NE BORDER. TEMPERATURES WILL ONLY DROP OFF INTO
THE LOWER TEENS AND BE STEADY FOR THE MORNING HOURS.
THE LONGER WAVE-LENGTH UPPER TROUGH WILL BEGIN TO ADVECT NORTHEAST
INTO THE MIDWEST BY LATE IN THE AFTERNOON. THIS SHOULD GRADUALLY
CAUSE THE LIGHT SNOW TO DIMINISH TO SNOW FLURRIES DURING THE
AFTERNOON HOURS. HIGHS SATURDAY WILL CONTINUE TO BE COLD WITH LOWER
TO MID 20S EXPECTED.
GARGAN
EXTENDED/SAT NIGHT-FRI/...
FAVOR A BLEND OF ECMWF/GFS FOR LATER PERIODS GIVEN THE DISCREPANCY
AND NO CLEAR PREFERENCE. ALL IN ALL WE WILL LEAN TOWARD COLDER TEMPS
GIVEN THE SNOW PACK AND CONTINUED INFLUENCE OF THE UPPER STORM
THROUGH SUNDAY. SOME LOW CHCS FOR LINGERING LIGHT SNOW APPEAR
WARRANTED SAT NIGHT BUT WE WILL TRY AND GO DRY BEGINNING SUNDAY AS
THE UPPER LOW SLOWLY FILLS AND DRIFTS EASTWARD AWAY FROM THE REGION.
BOTH THE ECMWF/GFS SHOW A WEAK SYSTEM RACING THROUGH THE REGION TUES
WITH WAA BRINGING A WARM UP WITH LOW CHCS FOR PRECIP. CURRENT FCST
CALLS FOR ANY PRECIP TO BE IN THE FORM OF SNOW AND THIS LOOKS
REASONABLE GIVEN THE LATEST 850MB TEMP AND MOISTURE PROFILE.
AFTER TUES...ECMWF DEVELOPS A DEEP UPPER LOW THAT USHERS IN ANOTHER
ROUND OF ARCTIC AIR BY LATE NEXT WEEK. THE GFS IS LESS AMPLIFIED
WITH THE TROUGH AND IS MORE PROGRESSIVE WHICH WOULD RESULT IN WARMER
CONDS.
CO
&&
.TOP WATCHES/WARNINGS/ADVISORIES...WINTER WEATHER ADVISORY UNTIL
6 AM SATURDAY FOR ALL OF THE FORECAST AREA KSZ008-KSZ009-
KSZ010-KSZ011-KSZ012-KSZ020-KSZ021-KSZ022-KSZ023-KSZ024-KSZ026-
KSZ034-KSZ035-KSZ036-KSZ037-KSZ038-KSZ039-KSZ040-KSZ054-KSZ055-
KSZ056-KSZ058-KSZ059.
&&
$$
