FXUS63 KTOP 151702
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1102 AM CST TUE DEC 15 2009

.DISCUSSION...UPDATED FOR 18Z AVIATION.

&&

.AVIATION...
VFR THROUGH THE PD. HIGH PRESSURE WILL MOVE EAST TOWARD THE GREAT
LAKES REGION THRU 18Z WEDNESDAY. SURFACE WIND WILL SHIFT AROUND TO
THE SOUTH AROUND MIDNIGHT. SLIGHT CONCERN FOR FOG AT MHK WHERE
THERE IS STILL SNOW ON THE GROUND CREATING A VERY SHALLOW MOIST
LAYER AS WEAK LLVL WARM ADVECTION BEGINS. HOWEVER...AFTER 09Z
WIND SPEEDS PICK UP ENOUGH TO WHERE IT COULD PREVENT FOG FROM
GETTING A START. WITH HIGH ENOUGH UNCERTAINTY WILL LEAVE IT OUT
FOR NOW.

CIRRUS WILL BE POSSIBLE TOWARD THE END OF THE TAF PD...NSW
EXPECTED. 

SALLY
&&
PREV DISCUSSION... /ISSUED 320 AM CST TUE DEC 15 2009/

DISCUSSION...

SURFACE HIGH PRESSURE AND VERY COLD AIRMASS CURRENTLY CENTERED
OVER EASTERN NEBRASKA THIS MORNING. UPPER FLOW WAS NORTHWESTERLY
WITH A TROUGH OVER THE SOUTHWEST CONUS PROVIDING A BIT OF A BAJA
MOISTURE FETCH INTO EASTERN OKLAHOMA. SKIES REMAIN CLOUD FREE OVER
TOP CWA AND TEMPS HAVE FALLEN TO NEAR ZERO IN NORTHERN KANSAS OVER
THE THICKER SNOW PACK AND INTO THE UPPER SINGLE DIGITS ELSEWHERE.

THE SURFACE HIGH PRESSURE WILL BUILD INTO NORTHEAST KANSAS DURING
THE DAY ON TUESDAY. 850 TEMPS WILL REMAIN WELL BELOW ZERO AND THE
COLD START WILL NOT HELP WARM US UP MUCH. DESPITE SUNSHINE AND
LIGHT WINDS...THE HEART OF THE COLD AIR WILL BE DIRECTLY OVERHEAD
AND THE DIURNAL VARIATION LOOKS TO BE ONLY AROUND 15 DEGREES F.
ANTICIPATE HIGH TEMPS ONLY IN THE LOWER TEENS OVER AREAS WELL
COVERED IN SNOW BUT WILL LIKELY SEE AT LEAST 20S OVER PARTS OF
EAST CENTRAL KANSAS.

A SLOW WARM UP...RELATIVELY SPEAKING...WILL BEGIN TONIGHT WITH
WARM AIR ADVECTION ON THE WEST SIDE OF THE DEPARTING HIGH
PRESSURE. UPPER FLOW WILL BECOME MORE ZONAL AS A DEEP TROUGH IS
PUSHED EAST ACROSS QUEBEC...ALLOWING FLOW TO FLATTEN OUT OVER MUCH
OF THE CONUS. MAIN FLY IN THE OINTMENT WILL BE JUST HOW MUCH SNOW
COVER AFFECTS THE TEMPERATURES. WITH 10 INCHES STILL ON THE GROUND
AT KCNK...ALBEDO IS NOT GOING TO ALLOW MUCH RADIATION TO BE
ABSORBED. THUS HAVE PLAYED SNOW COVER INTO TEMP FORECAST PRETTY
HARD WITH A STRONG GRADIENT FROM NORTH TO SOUTH.

A SHORT WAVE TROUGH DROPS DOWN THE FRONT RANGE OF THE ROCKIES
THURSDAY INTO FRIDAY. THIS WILL BRING ANOTHER SHOT OF COLD AIR
DOWN ACROSS THE PLAINS. MODEL TEMPS ARE TRENDING COLDER WITH THIS
SYSTEM...AND REASONABLY SO AS THE COLD AIR WILL NOT LIKELY BE ABLE
TO RETREAT VERY FAR NORTH WITH THE EXPANSIVE SNOW COVER. HAVE
FORECAST TOWARD THE COLD END OF GUIDANCE. GFS SOLUTION FOR
TIMING OF THE WAVE APPEARS TO BE REASONABLE. THE ENERGY WILL BE
DEEPENING AS IT APPROACHES KANSAS AND DYNAMICS APPEAR ABLE TO
CREATE SUFFICIENT LIFT FOR SNOW. MOISTURE IS A BIT OF A QUESTION
MARK BUT EXPECT THE COLUMN TO SATURATE DOWN AT SOME POINT AS THE
BEST LIFT MOVES THROUGH. DO NOT ANTICIPATE MUCH IN THE WAY OF
ACCUMULATIONS AT THIS POINT.

BARJENBRUCH

&&

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

&&

$$