FXUS61 KRLX 160853
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
345 AM EST WED DEC 16 2009
.SYNOPSIS...
HIGH PRESSURE IN CONTROL TODAY AND THURSDAY. SEASONABLY COLD...BUT
NOTHING UNUSUAL. MILDER WITH INCREASING CLOUDS FRIDAY. UPPER LEVEL
DISTURBANCE CROSSES THIS WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
H850 THERMAL TROUGH NOW PULLING ACROSS CWA...AND EXPECT IT TO EXIT
SHORTLY AFTER 12Z. MOISTURE IS ALSO BECOMING QUITE SHALLOW. THIS
WILL SPELL AN END TO ANY LINGERING FLURRIES OVER THE NORTHERN
MOUNTAINS.
HIGH PRESSURE IS THE NAME OF THE GAME FOR THE NEXT 24 HOURS...AS
CENTER MOVES FROM ILLINOIS THIS MORNING TO THE MIDDLE OHIO VALLEY BY
12Z THURSDAY. LOW LEVEL MOISTURE WILL ERODE THIS MORNING...LEAVING
PLENTY OF SUNSHINE FOR THE BALANCE OF THE DAY. TONIGHT...MODELS
INSIST ON BRINGING MOISTURE SOUTHEASTWARD ON THE NORTHERN SIDE OF
THE HIGH. THINK CLOUDS WILL BE ERODING A BIT AS THEY TRY TO DROP
IN...BUT COULD STILL SEE SOME SCATTERED STRATOCU OR MID/HI CLOUDS
AFTER MIDNIGHT.
DESPITE SUN...LEANED SLIGHTLY TOWARDS THE CHILLIER SIDE OF MOS
NUMBERS TODAY WITH NO REAL WARM ADVECTION OF NOTE. WINDS TONIGHT
WILL BE CALMER THAN THIS MORNING...BUT LEANED TOWARD A MET/MAV BLEND
FOR LOWS AS CLOUDS MAY LIMIT TEMPERATURE DROP AT LEAST LOCALLY.
&&
.SHORT TERM /THURSDAY THROUGH SATURDAY/...
IN THE BAROCLINIC ZONE OVER US...PATCHY CLOUDS AT HIGH STRATOCUMULUS
AND MID DECK FIGURED FOR THURSDAY...TENDING TO LIFT MORE TOWARD OUR
NORTHERN BORDER COUNTIES FOR THURSDAY NIGHT. 850 MB SOUTHWEST TO
NORTHEAST TEMPERATURE GRADIENT STILL AROUND 5C ACROSS OUR CWA ON
THURSDAY.
BUT WITH LIGHT WINDS...LIKED OUR PREVIOUS MAXIMUM TEMPERATURE
FORECAST...WHICH IS JUST UNDER MOST MOS GUIDANCE. THURSDAY SHOULD
NOT BE TOO HARD TO HANDLE FOR A DECEMBER DAY.
00Z MODELS AGREE IN KEEPING THE SOUTHERN MOISTURE TO OUR SE FRIDAY
INTO SATURDAY...WITH LOW PRESSURE OFF SE COAST. HAVE THE SEPARATE
WAVE IN THE OHIO VALLEY APPROACHING FRIDAY NIGHT. AHEAD OF THIS
WAVE...LIKED THE LOW LEVEL WARMING INDICATED BY THE NAM FOR FRIDAY.
SO INCREASED MAXIMUM TEMPERATURE FROM OUR PREVIOUS DETERMINISTIC
FORECAST. THE WAVE SHOULD PASS DURING SATURDAY. WITH COLDER AIR
AGAIN LATE SATURDAY AND SATURDAY NIGHT.
WITH THE LOW LEVEL WARMING...COULD SEE THE INITIAL PRECIPITATION
LATE FRIDAY NIGHT INTO SATURDAY...AS EITHER RAIN OR SNOW IN THE
SOUTHERN COUNTIES. 00Z NAM HAS 850-1000 THICKNESS STILL AROUND 1310
METERS AT 12Z SATURDAY.
DID A SLIGHT NONDIURNAL TEMPERATURE TRACE FOR THE HOURLY
TEMPERATURES FRIDAY NIGHT...WITH READING RISING SLIGHTLY 06Z TO 12Z
SATURDAY. ON SATURDAY HAD MAXIMUM TEMPERATURE AROUND 15Z...
WITH READINGS STEADY OR SLOWLY FALLING IN THE AFTERNOON.
LIKED OUR IDEA OF OUR HIGHER POPS TOWARD LATE SATURDAY INTO SATURDAY
NIGHT. STILL DOES NOT APPEAR TO BE ANY MEMORABLE MAJOR STORM ON THE
HORIZON.
&&
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
HI/LO CONFIDENCE FCST. RELATIVELY HIGH CONFIDENCE IN PNA PATTERN
WITH HIGH LATITUDE BLOCK TO BRING ABOUT BELOW NORMAL TEMPERATURES
FOR THE WEEKEND INTO THE HOLIDAY WEEK. LOW CONFIDENCE IN THE
DETAILS WITH VARIOUS SHORT WAVES MOVING THROUGH THE FLOW.
PERIOD BEGINS WITH UPPER LEVEL S/W OVER THE MIDWEST WITH POSITION /
TIMING DIFFERENCES ALREADY EVIDENT AMONG THE MODELS. DIFFERENCES
CONTINUE W/R WHERE THIS S/W GOES OVER THE WEEKEND INCLUDING WHERE IT
EXITS THE E COAST. THESE DIFFERENCES STEM...IN PART...FROM WHETHER
OR NOT UPPER LEVEL VORTEX LOBE OFF NOVA SCOTIA AT THE START OF THE
PERIOD RETROGRADES BACK OVER THE GREAT LAKES OR NOT. THERE IS LESS
MODEL AGREEMENT ON THIS SCENARIO THAN THERE WAS 24 HOURS AGO.
RETROGRESSION OF THE UPPER VORTEX WOULD ALLOW MORE SOUTHERLY FLOW
AHEAD OF MIDWEST S/W AND BRING ITS PRECIPITATION FARTHER N THAN
OTHERWISE. ACCEPTED HPC SOLUTION HERE WITH CHANCE POPS HIGHEST
ACROSS S HALF OF FCST AREA SAT NT.
ONCE THIS SYSTEM IS EXODUS SUNDAY...TRIED TO SHOW A BREAK BEFORE
ADDITIONAL SHORT WAVES IN THE FLOW ALOFT MOVE THROUGH. THERE IS
WIDE RANGE OF POSSIBILITIES W/R UPPER LEVEL PATTERN EARLY NEXT WEEK
ALTHOUGH BELOW NORMAL TEMPERATURES ARE IMPLIED...BUT HOW MUCH
BELOW? ECMWF AND GFS40 DO AGREE ON POLAR VORTEX OVER OR NEAR FCST
AREA SOMETIME EARLY NEXT WEEK.
USED BIAS CORRECTED MOSGUIDE FOR HIGHS SAT...THEN A MIX OF HPC AND
PREVIOUS FCST FOR HIGHS SUN-TUE. ROLLED WITH A BLEND OF THE BIAS
CORRECTED ADJMEX FOR LOWS SAT AND SUN MORNINGS...AND THEN PREVIOUS
FCST WITH SOME HPC BLENDING MON AND TUE MORNINGS...AND FINALLY CLOSE
TO A GFS40/ECMWF BLEND FOR WED MORNING...DAY 7 NIGHT.
&&
.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
00Z WEDNESDAY THRU 00Z THURSDAY...
DECREASING TREND IN CLOUDS/FLURRIES OVERNIGHT...WITH BORDERLINE MVFR
CIGS POSSIBLE IN THE MOUNTAINS THROUGH 13Z OR SO. GENERALLY VFR AFTER
SUNRISE WITH CLEARING SKIES AND LIGHT WINDS. SOME MID/HI CLOUDS
COULD FLOAT IN AFTER 00Z.
AFTER 06Z THURSDAY...
NO IFR WEATHER EXPECTED AT THIS TIME.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...KTB/CL
NEAR TERM...CL
SHORT TERM...KTB
LONG TERM...TRM
AVIATION...CL
