FXUS61 KRLX 061935
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
159 PM EST SUN DEC 6 2009
.SYNOPSIS...
HIGH PRESSURE MOVES ACROSS THE AREA TODAY. WEAK FRONT MONDAY
AFTERNOON. STRONGER SYSTEM LATE TUESDAY INTO WEDNESDAY...BRINGING
MIXED WINTRY PRECIPITATION.
&&
.NEAR TERM /THROUGH MONDAY/...
HIGH PRESSURE IN CONTROL. CIRRUS MOVING OVERHEAD IN ZONAL FLOW
ALOFT. EXPECT A SLOW LOWERING/THICKENING OF CLOUD COVER WITH SLOW
WARM ADVECTION COMMENCING ON THE BACK SIDE OF THE DEPARTING HIGH.
SHOULD NOT BE ENOUGH WARMING FOR A NONDIURNAL TRACE...BUT DID KEEP
LOW TEMPS AT OR A TOUCH ABOVE THE WARMER MOS GUIDANCE.
SHEARING H500 SHORTWAVE LIFTS FROM THE MID MISSISSIPPI VALLEY
OVERNIGHT INTO THE EASTERN GREAT LAKES BY 00Z TUESDAY. WEAK
ASSOCIATED FRONTAL BOUNDARY TRIES TO LEAK THROUGH DURING THE DAY.
PREFER THE FASTER GFS/ECMWF TIMING TO THE SLOWER NAM GIVEN THE ZONAL
FLOW PATTERN. WITH MIDLEVEL SUPPORT STAYING TO THE NORTH AND
MOISTURE FIELD SPLITTING AS IT MOVES ACROSS...DO NOT THINK THAT
ANYTHING MORE THAN SLIGHT CHANCE POPS ARE JUSTIFIED. ANY FLAKES WILL
BE CONFINED TO THE RIDGES WITH MODERATING SURFACE TEMPS AND H850
TEMPS OF AROUND -2 TO -3. MAIN EFFECT WILL BE AN INCREASE IN LOWER
CLOUDS...AS H850 MOISTURE LAGS BEHIND THE BOUNDARY. KEPT HIGHS AT OR
BELOW THE COOLER MOS VALUES...BUT HIGHS IN THE 40S ARE FORECAST MOST
EVERYWHERE.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
MID AND
HIGH CLOUDS WILL INCREASE ACROSS THE REGION SUNDAY NIGHT AS A
SHORTWAVE APPROACHES THE REGION FROM THE WEST. THIS SHORTWAVE WILL
SHEAR OUT AS MOVES TOWARDS THE GREAT LAKES ON MONDAY...WITH MOISTURE
BECOMING LIMITED AS IT DOES SO. A WEAK FRONTAL BOUNDARY ASSOCIATED
WITH THIS SHORTWAVE WILL ALSO PUSH THROUGH THE REGION ON MONDAY.
HAVE CONTINUED TO TREND THE FORECAST FOR THIS PERIOD TOWARDS THE GFS
AS IT IS PREFERRED OVER THE NAM. MODEL SOUNDINGS AND THICKNESSES
SUGGEST THAT PRECIPITATION WILL BE IN THE FORM OF RAIN ACROSS MUCH
OF THE REGION ON MONDAY...BEFORE CHANGING TO SNOW OR A RAIN SNOW MIX
OVERNIGHT.
HIGH PRESSURE WILL BUILD IN BRIEFLY BEHIND THE FRONT MONDAY
NIGHT/EARLY TUESDAY FOR A BRIEF BREAK IN THE
PRECIPITATION...ALTHOUGH A FEW UPSLOPE SNOW SHOWERS WILL CONTINUE TO
PERSIST LATE MONDAY NIGHT OVER THE HIGHER TERRAIN IN THE WNW FLOW
ALOFT.
A MORE POTENT SYSTEM WILL MOVE OUT OF THE SOUTHERN PLAINS AND INTO
THE REGION TUESDAY NIGHT. THIS SYSTEM IS CHARACTERIZED BY DEEP
MOISTURE...WITH PW VALUES GENERALLY AT AROUND AN INCH. COULD BE SOME
ELEVATED CONVECTION TUESDAY NIGHT/EARLY WEDNESDAY AS THIS SYSTEM
MOVES INTO THE REGION...MAINLY OVER THE SOUTHERN HALF OF THE
CWA...AS MODELS INDICATING 850MB THETA E RIDGE AND DECENT SHEAR OVER
THE REGION. HAVE ADDED THUNDER INTO THE FORECAST TO THIS TIME PERIOD
TO ACCOUNT FOR THIS. MUCH OF THE CWA WILL EXPERIENCE RAIN TUESDAY
NIGHT AND WEDNESDAY...HOWEVER...MODEL SOUNDINGS SUGGEST A WINTRY
MIX...INCLUDING PERIODS OF SLEET AND FREEZING RAIN OVER THE NORTHERN
MOUNTAIN ZONES. IN ADDITION GUSTY WINDS ARE EXPECTED AS A TIGHT
PRESSURE GRADIENT OF 10 TO 12 MB IS EXPECTED TO SET UP ACROSS THE
CWA...ALONG WITH A 50 TO 60 KT LOW LEVEL JET. PRECIPITATION WILL
BEGIN TO TAPER OFF LATE WEDNESDAY NIGHT AS THE LOW PRESSURE CENTER
MOVES OFF TO THE NORTHEAST. ANY LINGERING PRECIPITATION IS EXPECTED
TO CHANGE TO SNOW ON THE BACK SIDE OF THE LOW...WITH ONLY LIGHT
ACCUMULATIONS EXPECTED. HAVE TRENDED THE LATTER PART OF THE SHORT
TERM TOWARDS THE GFS...AS IT REMAINS THE PREFERRED MODEL FROM HPC.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
MEDIUM RANGE MODELS ARE SHOWING A SIGNIFICANT LOW PRESSURE SYSTEM
LIFTING UP THROUGH THE OHIO VALLEY MID WEEK...WITH LATEST RUNS
SLOWING ITS ASSOCIATED WARM FRONT AND ONSET OF PRECIP JUST A LITTLE.
THUS...HAVE TRIMMED POPS BACK TUESDAY TO MAINLY ACROSS THE SOUTH
LATER ON THE DAY TUESDAY...THEN RAPIDLY OVERSPREAD THE AREA TUESDAY
EVENING. THE TRACK OF THE LOW ITSELF IS THRU THE WESTERN OHIO
VALLEY...AND INTO MICHIGAN BY LATER IN THE DAY WEDNESDAY. THIS LOW
TRACK...AND STRONG HIGH PRESSURE RIDGING EAST OF THE MOUNTAINS...
WILL INHIBIT THE WARM FRONT FROM LIFTING NORTH THRU THE NORTHERN
MOUNTAINS TUESDAY NIGHT.
THUS...COLD AIR WILL BE TOUGH TO DISLODGE TUESDAY NIGHT AND EARLY
WEDNESDAY IN THE NORTHERN MOUNTAINS. FOR DETAILS...GOING WITH THE
COLDER GFS 850/925 TEMPS WITH THIS SYSTEM TUESDAY NIGHT AND EARLY
WEDNESDAY. THIS SCENARIO WILL KEEP MUCH OF THE PRECIP IN THE
FREEZING/FROZEN FORM TUESDAY NIGHT...ESPECIALLY ON EAST FACING
SLOPES OF THE NORTHERN MOUNTAINS. ELSEWHERE...WARMER AIR WILL RUSH
IN FAST ENOUGH TO GIVE MAINLY RAIN TUESDAY NIGHT AND EARLY WEDNESDAY
AHEAD OF THE WARM FRONT. BY MID MORNING WEDNESDAY...WARMER AIR WILL
FINALLY WIN OUT OVER THE ENTIRE AREA...WITH RAIN TURNING TO RAIN
SHOWERS IN THE WARM SECTOR. PURPOSELY KEPT QPF AMOUNTS LOW ENOUGH TO
PREVENT MENTION OF HEAVY ICE/SNOW IN THE NORTHERN MOUNTAINS AT THIS
EARLY DATE...BUT THE POTENTIAL IS THERE.
THE FOLLOWING COLD FRONT WILL RACE ACROSS THE AREA LATER ON
WEDNESDAY. RAIN SHOWERS ON WEDNESDAY WILL RAPIDLY CHANGE TO SNOW
SHOWERS WEDNESDAY EVENING. THERE WILL LIKELY BE SOME SNOW
ACCUMULATIONS ACROSS MUCH OF THE AREA BY THURSDAY
MORNING...ESPECIALLY MOUNTAINS. HIGH PRESSURE BUILDS IN THURSDAY
WITH SNOW SHOWERS ENDING.
THIS WILL BE A WINDY SYSTEM GIVEN THE STRENGTH OF THE LOW. LOOK FOR
GUSTY SOUTH WINDS DEVELOPING TUESDAY AND TUESDAY NIGHT...ESPECIALLY
MOUNTAIN RIDGETOPS. GUSTY WINDS WILL CONTINUE THRU WEDNESDAY...AND
AFFECT MORE OF THE AREA...AS WINDS TURN MORE WESTERLY WITH THE COLD
FRONT. DID NOT WANT TO PUSH ADVISORY WIND CRITERIA AT THIS EARLY
DATE...BUT THE POTENTIAL IS THERE MAINLY FOR RIDGETOPS.
BEYOND THURSDAY...ANOTHER SYSTEM WILL AFFECT THE AREA FRIDAY AND
SATURDAY...WITH MORE UNSETTLES WEATHER AND BELOW NORMAL TEMPS.
&&
.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
VFR THROUGH THE PERIOD WITH LIGHT SW FLOW. HIGH THIN CLOUD COVER WILL
SLOWLY LOWER AND THICKEN WITH TIME...SUCH THAT CIGS OF AROUND 7-9
THOUSAND FEET ARE EXPECTED BY 15Z OR SO ON MONDAY. SHOULD BE ENOUGH
CLOUD OVERNIGHT TO PRECLUDE ANOTHER FOG PERFORMANCE. COULD SEE A
COUPLE OF ISOLATED SHOWERS SNEAK INTO SOUTHEAST OHIO AROUND 18Z
AHEAD OF A COLD FRONT...BUT MOISTURE IS LIMITED AND CHANCES ARE LOW.
AFTER 18Z MONDAY...
IFR IN MOSTLY RAIN LATE TUESDAY INTO WEDNESDAY.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...KTB/CL/JMV
NEAR TERM...CL
SHORT TERM...KTB
LONG TERM...JMV
AVIATION...CL
