837
FXUS63 KTOP 202350
AFDTOP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
550 PM CST FRI NOV 20 2009
UPDATE
UPDATE FOR 0Z AVIATION.
DISCUSSION
SEE PREVIOUS DISCUSSION.
AVIATION
HAVENT CHANGED MUCH FROM PREVIOUS FORECASTS...WITH A SLOW DOWNTURN
EXPECTED THIS EVENING AND OVERNIGHT...THOUGH CONFIDENCE IN
SPECIFIC TIMING IS LOW. TEMPS ALREADY FALLING OF QUICKLY...AND
WILL BRING MVFR CONDITIONS IN EARLIER AS A RESULT. DEEP MOISTURE
TO THE SOUTH MAY KEEP LIFR TO IFR RESTRICTIONS IN PLACE THROUGH
MUCH OF THE DAY SATURDAY...AND TRENDED THIS WAY. FORECAST
SOUNDINGS STILL SUPPORT FG DEVELOPMENT BEFORE STRATUS...THOUGH
RECENT IR IMAGERY AND OBS NOT FAR SOUTH SHOWING SOME VFR STRATUS
ALREADY DEVELOPING.
65
PREV DISCUSSION
/ISSUED 306 PM CST FRI NOV 20 2009/
DISCUSSION...
SHORT TERM (THROUGH SATURDAY)...
THE PRIMARY FORECAST CONCERN IN THE SHORT TERM IS THE POSSIBILITY OF
DENSE FOG ONCE AGAIN LATE TONIGHT AND INTO SATURDAY MORNING.
THE CENTRAL PLAINS ARE CURRENTLY TRAPPED BETWEEN STORM SYSTEMS AS A
SIGNIFICANT RAIN MAKER IS IN PLACE OVER TEXAS...THE TROUGH PRODUCING
OUR WET WEATHER EARLIER THIS WEEK HAS MOVED OFF TO THE NORTHEAST...
AND A LARGE TROUGH IS NOW MOVING ON TO NORTHERN PORTIONS OF THE WEST
COAST. AT THE SURFACE A BROAD AREA OF HIGH PRESSURE IS SITUATED
ACROSS NORTHERN KANSAS...PROVIDING DRY SINKING AIR...LIGHT
WINDS...AND CLEAR SKIES THIS AFTERNOON.
THE LIGHT WINDS WILL CONTINUE THROUGH THE OVERNIGHT HOURS. HIGH
CLOUDS SHOULD BE CONFINED TO SOUTHEASTERN PORTIONS OF KANSAS...SO
RADIATIONAL COOLING WILL BE STRONG OVER THE I-35 CORRIDOR AND POINTS
NORTH AND WEST. FORECAST SOUNDINGS INDICATE THAT A STRONG INVERSION
WILL FORM OVER THESE AREAS AND TEMPS WILL FALL BELOW THE CROSSOVER
TEMPERATURE AND ESSENTIALLY SHOULD REACH 100 PERCENT RH THROUGH THE
LOWEST 1000 FEET BY EARLY MORNING. FOG WILL LIKELY DEVELOP WITH SOME
DENSE FOG POSSIBLE NEAR SUNRISE. ANTICIPATE THE DEPTH OF MOISTURE TO
INCREASE FROM SOUTH TO NORTH OVERNIGHT WHICH MAY PROMOTE ADDITIONAL
LOW STRATUS AND FOG DEVELOPMENT. CONFIDENCE IN THE OVERALL DENSITY
OF FOG...AND LOCATION OF POTENTIAL DENSE FOG IS NOT HIGH AT THE
MOMENT SO HAVE HELD OFF ON ISSUING A DENSE FOG ADVISORY UNTIL THE
DETAILS SORT THEMSELVES OUT A LITTLE BETTER.
SATURDAY TEMPERATURES WILL BE MILD ONCE AGAIN...BUT CLOUD COVER WILL
BE MORE PREDOMINANT THAN TODAY. CURRENTLY LOOKS LIKE THE FOG WILL
LIFT INTO A STRATUS DECK AND PERSIST THROUGH A GOOD PART OF THE DAY
WITH MOISTURE ADVECTION ALOFT FROM THE SOUTH. GFS IS ATTEMPTING TO
OUTPUT SOME LIGHT PRECIP...BUT LIFT APPEARS MARGINAL AND OVERALL
MOISTURE DEPTH IS LACKING. MAY SEE A BIT OF DRIZZLE BUT DO NOT
EXPECT ACCUMULATING PRECIP.
BARJENBRUCH
LONG TERM (SATURDAY NIGHT THROUGH FRIDAY)...
SATURDAY NIGHT AND SUNDAY NIGHT...AN UPPER LEVEL TROUGH OVER THE
WESTERN CONUS WILL FILL AS IT MOVES EAST ACROSS THE PLAINS.
LOW-LEVEL WAA OF RESIDUAL MOISTURE WILL CAUSE DRIZZLE AND AREAS OF
FOG TO FORM SATURDAY NIGHT INTO SUNDAY MORNING. THERE MAY BE ENOUGH
ASCENT AHEAD OF THE WEAKENING UPPER TROUGH FOR ISOLATED RAIN SHOWERS
OR SPRINKLES THROUGH THE DAY SUNDAY. SUNDAY HIGHS WILL BE DEPENDENT
ON CLOUD COVER...IF SKIES BECOME PARTLY CLOUDY DURING THE AFTERNOON THEN
HIGHS MAY BE IN THE MID TO UPPER 50S. HOWEVER...IF WE KEEP THE LOW
STRATUS THROUGH THE DAY THEN HIGHS WILL BE MUCH COOLER...MAY ONLY
SEE THE UPPER 40S TO AROUND 50.
MONDAY THROUGH TUESDAY NIGHT...A SECOND UPPER LEVEL TROUGH WILL MOVE
ONSHORE ACROSS THE PACIFIC NORTHWEST AND DIG SOUTHEAST ACROSS THE
PLAINS. THE 12Z RUN OF THE EC DIGS THE 5H TROUGH FARTHER WEST ACROSS
THE HIGH PLAINS LATE MONDAY AFTERNOON THEN LIFTS THE AMPLIFIED UPPER
TROUGH EAST AND NORTHEAST ACROSS THE STATE OF KS. MEANWHILE...THE
12Z GFS DIGS THE UPPER LEVEL TROUGH ACROSS THE CENTRAL
PLAINS...SOUTHEAST INTO THE MID MS RIVER VALLEY. THE 12Z RUN OF THE
NAM LOOKS TO BE SOMEWHERE BETWEEN THE EC AND GFS SOLUTIONS. IF THE EC
SOLUTION WERE TO VERIFY WE WOULD HAVE A BETTER CHANCE FOR RAIN
MONDAY AFTERNOON...CHANGING OVER TO SNOW THROUGH THE NIGHT
ACROSS THE NORTHERN COUNTIES OF THE CWA...THOUGH THE BEST TROWAL SET
UP WOULD BE NORTH OF THE CWA ACROSS EASTERN NE. THE GFS SOLUTION
WOULD BE MUCH DRIER WITH THE MOST OF THE FORCING AND ASCENT
REMAINING NORTH AND EAST OF THE CWA. THE NAM MODEL SOLUTION SHOWS
THE UPPER TROUGH DIGGING SOUTHEAST ACROSS NORTHERN KS...SO THERE
WOULD BE A BETTER CHANCE FOR RAIN POSSIBLY MIXING WITH SNOW ACROSS
THE NORTHERN COUNTIES OF THE CWA LATE MONDAY NIGHT. I PLACED IN A MIX OF
RAIN AND SNOW ACROSS NORTH CENTRAL KS MONDAY NIGHT IN CASE THE NAM
AND EC CONTINUE TO CONVERGE ON THEIR CURRENT SOLUTIONS. HIGHS ON TUESDAY
WILL ONLY REACH THE MID 40S TO LOWER 50S DUE TO CLOUD COVER AND
PRECIP CHANCES.
THE END OF NEXT WEEK COULD BE TURNING SHARPLY COOLER AS BOTH THE EC
AND GFS SHOW A LONGER WAVE LENGTH UPPER LEVEL TROUGH DEVELOPING
ACROSS THE CENTRAL CONUS. IF WE KEEP NORTHWEST FLOW ALOFT WE MAY NOT
SEE MUCH IN THE WAY OF PRECIPITATION DURING THIS PERIOD. HIGHS
WEDNESDAY THROUGH FRIDAY WILL BE IN THE MID 40S TO AROUND 50 WITH
OVERNIGHT LOWS IN THE MID 20S TO LOWER 30S.
GARGAN
TOP WATCHES/WARNINGS/ADVISORIES
NONE.
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