FXUS61 KRLX 300240
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
934 PM EST SUN NOV 29 2009
.SYNOPSIS...
COLD FRONT BRINGS RAIN SHOWERS OVERNIGHT INTO MONDAY...ENDING AS
SNOW SHOWERS MONDAY NIGHT. HIGH PRESSURE RETURNS TUESDAY. LOW
PRESSURE PASSES THURSDAY MORNING. COLDER THURSDAY NIGHT AND FRIDAY.
&&
.NEAR TERM /THROUGH MONDAY/...
UPDATED TEMPERATURES VIA LAV TO REFLECT WARM NOCTURNAL AIR AHEAD OF
COLD FRONT...WHICH STILL DEPICT WET BULB COLLING WHEN THE RAIN
BEGINS. THIS RESULTS IN HIGHER OVERNIGHT LOWS AND SLIGHTLY HIGHER
HIGHS FOR MON. BALANCE OF THE NEAR TERM FCST IS ON TRACK
NOTWITHSTANDING A LEAD SHORT WAVE GOING THROUGH DURING THE EVENING..
REST PREV...
MID/HI CLOUDS WILL CONTINUE TO THICKEN DURING THE REMAINDER OF THE
AFTERNOON. NEAREST RAIN REACHING THE GROUND IS BACK IN
INDIANA...NOT TOO FAR AHEAD OF FRONTAL BOUNDARY.
THIS FRONT IS THE STORY TONIGHT AND MONDAY. MODELS IN PRETTY DECENT
AGREEMENT ON TIMING. IT WILL PICK UP SPEED AS THE H500 SHORTWAVE
CURRENTLY OVER THE UPPER MIDWEST DIGS INTO THE EASTERN GREAT LAKES
BY MONDAY MORNING. THINK FRONT ENCROACHES THE WESTERN CWA BOUNDARY
AROUND 06Z...REACHES CRW BY 09Z...AND IS IN THE MOUNTAINS BY 12Z.
RAINFALL APPEARS TO BE MAINLY ALONG AND BEHIND FRONT. HAVE
CATEGORICAL POPS SET UP THIS WAY. SYSTEM WILL BE ABLE TO SCOOP UP
SOME OF THE MOISTURE OVER THE LOWER MISSISSIPPI VALLEY...WITH PWATS
JUST AHEAD OF FRONT BUILDING TO .75-1.0 INCH. STILL...SPEED OF
FRONT WILL LIMIT RAIN TOTALS TO AROUND .20 TO .30 INCH. MAY BE JUST
ENOUGH TO PREVENT AN ALL-TIME DRIEST NOVEMBER AT CRW.
COLDER AIR SPILLS IN BEHIND FRONT...WITH H850 0C LINE THROUGH CWA BY
21Z MONDAY. EXPECT LOW CLOUDS TO LINGER BEHIND FRONT FOR SOME
TIME...WITH LATE CLEARING IN THE WEST. ONCE AGAIN...BOUNDARY LAYER
COOLING WILL LAG A BIT. ONLY FORESEE ANY SNOW CHANGEOVER BEFORE 00Z
AT OR ABOVE 2000 FEET...WITH LITTLE ACCUMULATION. PRECIP TAKES ON
AN UPSLOPE CHARACTER THROUGH THE NIGHT WITH NW FLOW BEHIND SYSTEM.
MOISTURE DEPTH DECREASES RAPIDLY THOUGH...AND COULD EVEN SEE DRIZZLE
AND/OR FREEZING DRIZZLE LATE MONDAY AS ICE CRYSTAL AVAILABILITY
COMES INTO QUESTION...CLOUD TOPS MAY BE WARMER THAN -10C.
USED BIAS-CORRECTED SREF FOR LOWS TONIGHT...WHICH WAS IN DECENT
AGREEMENT WITH MOS. FROPA ON MONDAY CALLS FOR AN EARLY HIGH AND A
SLOW FALL IN TEMPS DURING THE DAY. MAX VALUES CLOSEST TO MAV.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
FRONT MOVES EAST OF THE WEST VIRGINIA MOUNTAINS MONDAY NIGHT WITH
SURFACE HIGH PRESSURE. RESIDUAL MOISTURE...NORTHWEST FLOW AND A WEAK
85H THERMAL TROUGH WILL BE IN PLACE UNTIL TUESDAY MORNING. THESE
FACTORS SHOULD COMBINE TO ALLOW FOR A FEW LIGHT SNOW SHOWERS TO
CONTINUE OVER THE EASTERN MOUNTAINS FOR A LIGHT DUSTING OF SNOW.
SFC HIGH PRESSURE SLIDES QUICKLY TO THE EAST TUESDAY WITH WAA ALONG
WITH OVER-RUNNING HIGH CLOUDS. NEXT SYSTEM TO ORGANIZE ALONG THE
GULF COAST AND TRACK NORTHWARD INTO THE TN VALLEY. FAIRLY
SIGNIFICANT MOISTURE AND DYNAMICS AND MOISTURE ASSOCIATED WITH THIS
SYSTEM...AND MODELS STILL HAVING HARD TIME GETTING A DECENT HANDLE
ON THE DETAILS.
GFS CONTINUES TO BE THE MORE PROGRESSIVE...SHIFTING THE CUT-OFF LOW
OUT OF THE SOUTHWESTERN US EARLIER THAN THE ECMWF. THIS TRANSLATES
INTO A MORE RAPID ONSET OF PRECIP FOR WEDNESDAY. HEDGED THE FORECAST
A LITTLE CLOSER WITH THE ECMWF TIMING...KEEPING SOME INFLUENCES OF
THE GFS IN PLACE. FOR TEMPS...MOS BC GRIDS LOOKED ON TRACK ON CLOSE
TO CURRENT NUMBERS IN PLACE.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
THE STRONG WAVE MAY GO WEST OF THE MOUNTAINS THURSDAY MORNING. WILL
BASE THIS FORECAST WITH HPC THINKING THAT THE RECENT RUNS GFS RUNS
THROUGH 12Z WERE ON THE FAST SIDE OF THE ENVELOPE. WILL GO ABOUT 6
HOURS SLOWER FOR OUR DETERMINISTIC HOURLY GRAPHICS.
DESPITE THE SIGNIFICANT SE FLOW INTO OUR UPSLOPE...DO NOT THINK IT
WILL BE COLD ENOUGH FOR ANY MIXED PCPN WEDNESDAY NIGHT. HAVE ALL
RAIN THEN. DID INCREASE THE SURFACE WINDS FOR AOA 2000 FEET
WEDNESDAY NIGHT.
WITH THAT TIMING...HAVE TEMPERATURES FALLING WEDNESDAY
EVENING...THEN LEVELING OFF AND RISING DURING THE PREDAWN...THEN
FALLING THURSDAY AFTERNOON. SO A NONDIURNAL FOR BOTH WEDNESDAY
NIGHT AND AGAIN ON THURSDAY. HAVE THE RAIN CHANGING TO SNOW SHOWERS
THURSDAY AFTERNOON.
WITH THE 500 MB TROF STILL HOLDING BACK OVER THE MIDWEST...TO OUR
WEST...AND THE 850 THERMAL TROF STILL TO OUR WEST...WENT
BELOW/COLDER THAN HPC GUIDANCE TEMPERATURES FOR FRIDAY INTO
SATURDAY. HAVE POPS HIGHER THAN HPC FOR UPSLOPE SNOW SHOWERS
THURSDAY NIGHT INTO FRIDAY. ALSO...LOW LEVEL MOISTURE MAY ALSO
LINGER LONGER...INTO SATURDAY...SO STILL HAVE SOME 20 POPS LINGERING
IN MANY AREAS.
&&
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
VFR CONDITIONS EARLY ON...ALTHOUGH CLOUDS WILL BE LOWERING AND
THICKENING. COLD FRONT WILL MOVE ACROSS AREA BETWEEN 09Z AND
18Z...WITH MUCH OF ITS PRECIPITATION IMMEDIATELY ALONG AND BEHIND
IT. EXPECTING MVFR CIG/VIS CLOSE TO THE FRONT...WITH IFR CIGS
DEVELOPING FOR A TIME BEHIND THE FRONT IN THE COOLER AIRMASS.
POSSIBLE CHANGEOVER TO SNOW IN THE MOUNTAINS TOWARD 00Z MONDAY.
SW FLOW A BIT GUSTY AT TIMES AHEAD OF THE FRONT SHIFTING TO WNW
10KTS OR LESS IN ITS WAKE. MODERATE TO STRONG SW FLOW ALOFT
SWITCHES TO LIGHT TO MODERATE NW FLOW ALOFT ONCE THE FRONT PASSES.
AFTER 00Z TUESDAY...
BRIEF IFR CONDITIONS POSSIBLE DUE TO LINGERING LIGHT SNOW ALONG THE
HIGHER WEST FACING SLOPES OF THE MOUNTAINS MONDAY EVENING.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...CL/KMC/KTB
NEAR TERM...CL/TRM
SHORT TERM...KMC
LONG TERM...KTB
AVIATION...TRM
