FXUS63 KTOP 220545
AFDTOP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1145 PM CST MON DEC 21 2009
.UPDATE...
UPDATED FOR THE 06 UTC AVIATION.
&&
.DISCUSSION...
SEE THE PREVIOUS DISCUSSION.
&&
.AVIATION...
HIGH CLOUDS WILL OVERSPREAD THE TAF SITES THIS MORNING. 925MB
WINDS HAVE INCREASED FROM THE SOUTH AT 30 KTS AND SHOULD SLOWLY
VERY THROUGH THE MORNING HOURS. THERE MAY BE SOME MODERATE LOW-
LEVEL WIND SHEAR AT THE TAF SITES THROUGH 15Z. DEEPER MOISTURE WILL
ADVECT NORTHWARD ABOVE THE INVERSION AND CAUSE LIGHT FOG AND MVFR
CEILINGS TO FORM BY DAY BREAK. A COLD FRONT WILL PUSH THROUGH THE
TAF SITES BY 16Z AND WINDS WILL BECOME NORTHEASTERLY. LOW STRATUS
BEHIND THE FRONT WILL CAUSE CEILINGS TO DROP BELOW IFR LEVELS
THROUGH THE AFTERNOON AND EVENING HOURS. THERE MAY ALSO BE SOME
PATCHY DRIZZLE. IF KMHK FALLS BELOW FREEZING THERE COULD BE SOME
PATCHY -FZDZ AT KMHK THROUGH THE EVENING HOURS.
GARGAN
&&
.PREV DISCUSSION... /ISSUED 324 PM CST MON DEC 21 2009/
DISCUSSION...
TONIGHT THROUGH TOMORROW...
WATER VAPOR IMAGERY AT 19Z SHOWING A SHORTWAVE MOVING EASTWARD
ACROSS WESTERN KS. THIS SHORTWAVE IS ONLY PRODUCING SOME MID AND
HIGH CLOUDS. THE SOUTH/SOUTHEASTERLY WINDS AND ONLY SCT-BKN CIRRUS
HAVE ALLOWED TEMPS TO RISE INTO THE 30S ACROSS SNOW COVERED AREAS
NORTH TO THE MID/UPPER 40S CENTRAL AND SOUTH. THE SHORTWAVE WILL
HELP TO PUSH A FRONT NOW OVER WESTERN NE SOUTHEAST INTO THE COUNTY
WARNING AREA (CWA) ON TUESDAY WHICH WILL SLOW DOWN AS IT APPROACHES
THE TURNPIKE. THIS WILL ALLOW FOR THE MILDER AIR TO REMAIN TONIGHT
ACROSS THE SOUTHERN CWA WITH LOWS IN THE LOWER 30S...WHILE COLDER
AIR FILTERS BACK INTO THE NORTHERN CWA WITH READINGS FALLING INTO
THE MIDDLE AND UPPER 20S.
MOISTURE WILL BE ADVECTING NORTHWARD LATER TONIGHT FROM OK WHICH
WILL ALLOW STRATUS TO DEVELOP ACROSS MUCH OF THE CWA...BUT WITH SUCH
SHALLOW MOISTURE AND LITTLE IN THE WAY OF LIFT...WILL GO
DRY...ALTHOUGH SOME PATCHY FOG IS POSSIBLE ACROSS
THE SOUTH AND WEST AREAS WITHIN THE MOISTURE ADVECTION. THE BOUNDARY
BISECTING THE CWA WILL PRODUCE A SIGNIFICANT TEMP GRADIENT FOR HIGHS
WITH READINGS EXPECTED TO RANGE FROM NEAR FREEZING ACROSS THE FAR
NORTH TO THE MIDDLE 40S EAST CENTRAL. AS THE LLVL FLOW BACKS DURING
THE DAY...CANNOT RULE OUT SOME AREAS OF MORNING FOG...THEN
SOME PATCHY DRIZZLE ACROSS THE CENTRAL AND SOUTH AND PATCHY DRIZZLE
OR LIGHT FREEZING DRIZZLE NORTH IN THE AFTERNOON.
62
TOMORROW NIGHT THROUGH FRIDAY...
COMPLEX STORM SYSTEM GATHERING STRENGTH OFF THE WEST COAST STILL
HASN'T SHOWN ITS HAND AS OF YET AND MANY FINE DETAILS ARE TOO FAR
OUT TO PAINT A COMPLETE PICTURE. WHAT I AM HIGHLY CONFIDENT IN IS
A VERY STRONG WINTER STORM AFFECTING NORTHEASTERN KANSAS WEDNESDAY
NIGHT INTO FRIDAY.
MODEL SOLUTIONS HAVEN'T CONVERGED AS OF YET...BUT HPC CONSENSUS IS
TO USE ECMWF ENSEMBLE AND GFS BLEND. THIS MOVES THE UPPER LOW
SOUTH OF THIS AREA WITH THE SURFACE LOW MOVING ALONG THE KS/MS
STATE LINE. IF THIS IS THE CASE...ECMWF AND GFS BOTH BRING AN
IMPRESSIVE TROWEL FEATURE DIRECTLY OVER THIS AREA. FRONTOGENESIS
DIAGNOSTICS AND MOISTURE PROFILES ALL POINT TO A SUSTAINED HEAVY
SNOW EVENT.
AS THE TROF DEEPENS AND BECOMES NEGATIVELY TILTED, SURFACE LOW
WILL LIKELY BOTTOM OUT AND SLOW DOWN JUST SOUTHEAST OF KANSAS
CITY. AREAS JUST EAST OF LOW COULD EVEN SEE THUNDERSTORMS IN
STRONG WARM ADVECTION BELT. COLD AIR BEHIND SYSTEM IS ALSO DEEP
AND PLENTIFUL...AND INVASION BEHIND THE LOW WILL BE FULL FORCE
WITH 40 MPH OR HIGHER SURFACE WINDS. THIS WILL LEAD TO VERY
DANGEROUS CONDITIONS OVERNIGHT ON THURSDAY INTO FRIDAY. AM STILL
NOT CONFIDENT ENOUGH WITH LOW TRACK TO MENTION SPECIFIC SNOW
AMOUNTS...ALTHOUGH WARNING CRITERIA AMOUNTS OVER SIX INCHES ARE
LIKELY.
SOME CHANGES WERE MADE FROM PREVIOUS FORECAST AS NEW GUIDANCE IS
WARMER. BECAUSE OF THIS...I REMOVED MOST OF THE FREEZING
RAIN/DRIZZLE FROM MY FORECAST. INVERTED SURFACE TROF SHOULD STAY
WEST OF CONCORDIA KANSAS....AND THIS KEEPS TEMPS ABOVE FREEZING
UNTIL WEDNESDAY NIGHT. RAPID CHANGE TO SNOW WITH DETERIORATING
CONDITIONS WILL WORK ACROSS EASTERN KANSAS THOUGH OUT THE DAY
THURSDAY. THURSDAY NIGHT WILL BE THE BRUNT OF THE STORM. EXPECT
ACCUMULATING SNOW TO END EARLY FRIDAY MORNING WITH CONTINUED
BLOWING AND DRIFTING THROUGH EARLY AFTERNOON.
SATURDAY THROUGH MONDAY...AS THE STORM SYSTEM DEPARTS THE
AREA...COLD ARCTIC AIR RUSHES IN BEHIND THE BRISK NORTHWEST FLOW.
OVERNIGHT LOWS WILL DROP INTO THE UPPER SINGLE DIGITS ACROSS THE
NORTHWESTERN PART OF THE CWA...WHILE FURTHER TO THE EAST AND
SOUTHEAST TEMPERATURES THROUGH THE WEEKEND WILL DROP INTO THE LOW TO
MID TEENS. SKIES WILL ALSO GRADUALLY CLEAR OUT AS HIGH PRESSURE
MAKES ITS WAY BACK INTO THE AREA LATE IN THE WEEKEND.
HARDING
&&
.TOP WATCHES/WARNINGS/ADVISORIES...WINTER STORM WATCH FROM 6 PM WEDNESDAY TO NOON FRIDAY FOR KSZ008-
KSZ009-KSZ010-KSZ011-KSZ012-KSZ020-KSZ021-KSZ022-KSZ023-KSZ024-
KSZ034-KSZ035-KSZ036-KSZ037.
&&
$$
