FXUS61 KRLX 231042
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
540 AM EST WED DEC 23 2009
.SYNOPSIS...
HIGH PRESSURE TODAY AND TONIGHT...SHIFTS EAST AS TEMPERATURES TURN
WARMER THURSDAY. RAINY AND BREEZY OCCLUDED FRONT EXPECTED THURSDAY
NIGHT THROUGH CHRISTMAS. TURNING COLDER AGAIN THIS WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
MAIN WEATHER INFLUENCE WILL BE A SURFACE HIGH OVER THE GREAT
LAKES...WITH ITS RIDGE EXTENDING DOWN OVER OUR REGION. WEAK IMPULSE
HEADING FROM WESTERN TO CENTRAL OHIO AT 4AM THIS MORNING...WILL
GRADUALLY FALL APART AS IT RUNS INTO THE SURFACE RIDGE...BUT A FEW
FLURRIES MAY GET INTO THE NORTHWESTERN ZONES LATER THIS MORNING.
THE HIGH IS MANAGING TO ADVECT IN DRIER AIR AT THE SURFACE...OUT OF
THE NORTH/NORTHEAST...WHICH HAS REALLY EATEN AWAY AT THE LOW CLOUDS.
THOUGH POCKETS OF VALLEY FOG WILL START OFF THE MORNING IN THE
CENTRAL TO SOUTHERN LOWLANDS...THESE WILL QUICKLY ERADICATE BECAUSE
OF THE DRIER LOW LEVEL AIR. MEANWHILE...CLOUDS WILL BE MAINLY THE
HIGH VARIETY.
DESPITE WARM AIR ADVECTION BEGINNING ALOFT TODAY...VERY STABLE LOW
LEVEL PROFILE WILL PREVENT THIS FROM BEING REALIZED AT THE
SURFACE...WITH THE MORE SIGNIFICANT WARMING WAITING UNTIL AFTER THE
NEAR TERM PERIOD. MAX TEMPERATURE FORECAST A MODEL BLEND...BUT FOR
MINIMUM TEMPERATURES A BIT MORE COMPLICATED. FAIRLY WIDE SPREAD IN
GUIDANCE NUMBERS FOR TONIGHT...AND I LEANED TO COLD END OF GUIDANCE
IN THE NORTHEASTERN ZONES WHERE BETTER RADIATIONAL COOLING AND
SNOWPACK WILL HELP THOSE NUMBERS BE REALIZED...IN ADDITION TO BEING
MORE UNDER THE INFLUENCE OF THE DEPARTING SURFACE RIDGE. IN THE
CENTRAL TO SOUTHWEST...NOT AS GOOD FOR RADIATIONAL COOLING BECAUSE
OF HIGH CLOUDS...THUS BLENDED GUIDANCE SEEMED MORE REASONABLE.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
NOT MUCH CHANGE FROM PREVIOUS MODEL RUNS. STRONG LOW PRESSURE WILL
LIFT WELL NORTH AND WEST OF OUR AREA CHRISTMAS EVE AND CHRISTMAS
DAY. WARM FRONT WILL LIFT NORTH CHRISTMAS EVE NIGHT...FOLLOWED BY A
COLD FRONT CHRISTMAS DAY. STRONG SURFACE HIGH PRESSURE RIDGING
SOUTHWARD EAST OF THE MOUNTAINS WILL BE SLOW TO GET DISLODGED BY THE
APPROACHING SYSTEM. THE ONE CHANGE IS THAT MODELS PUT US IN A
RELATIVE DRY SLOT FRIDAY NIGHT INTO SATURDAY BEHIND THE COLD
FRONT...BEFORE WRAPAROUND MOISTURE AND COLD ADVECTION COME BACK IN
FORCE DURING SATURDAY.
EXPECT MAIN PRECIP BAND TO DEVELOP ACROSS THE AREA THURSDAY
NIGHT...AND LIFT OUT WITH THE WARM FRONT FRIDAY MORNING. AROUND A
HALF INCH OF RAINFALL IS EXPECTED MOST AREAS...WHICH SHOULD NOT BE
ENOUGH TO CAUSE SIGNIFICANT FLOODING WITH THE MELTING SNOW PACK.
HOWEVER...IF MORE RAINFALL OCCURS...THEN THIS WOULD BECOME MORE OF A
PROBLEM. FOR NOW...NO MENTION OF FLOODING ISSUES.
WITH THAT STRONG HIGH ONLY SLOWLY GIVING WAY...STILL LOOKS LIKE AN
ICING EVENT SETTING UP FOR MAINLY EAST FACING SLOPES OF THE NORTHERN
AND CENTRAL MOUNTAINS THURSDAY NIGHT INTO FRIDAY MORNING...BEFORE
WARM AIR FINALLY ERODES THE COLD AIR DAMMED UP AGAINST THE
MOUNTAINS. THIS MAY LEAD TO AN ADVISORY OR WARNING...BUT STILL LOTS
OF TIME FOR DAY SHIFT TO EVALUATE FURTHER. IN ANY EVENT...THE WARM
AIR WILL WIN OUT LATER FRIDAY MORNING. TEMPERATURES WILL REALLY
REBOUND AHEAD OF THE COLD FRONT FRIDAY...WITH GUSTY SOUTH WINDS.
WINDS MAY ALSO BE AN ISSUE IN THE MOUNTAINS FRIDAY WITH A 60 TO 70
KT 850 MB SOUTHERLY JET FORECAST. AGAIN...WILL LET DAY SHIFT FURTHER
EVALUATE.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
DEEP COLD CYCLONIC FLOW WILL INCREASE ACROSS THE AREA ON
SATURDAY...WITH INCREASING SNOW SHOWERS BY SATURDAY NIGHT. THIS WILL
CONTINUE THRU THE WEEKEND...AS THE UPPER LOW TRACKS EASTWARD ACROSS
THE AREA. SOME SNOW ACCUMULATION EXPECTED...ESPECIALLY IN THE
MOUNTAINS.
HIGH PRESSURE BUILDS IN EARLY/MID NEXT WEEK FOR DRIER AND SLIGHTLY
WARMER WEATHER.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
TRICKY BALANCE OF FACTORS THIS MORNING...WITH LOW LEVEL MOISTURE IN
THE BOUNDARY LAYER TRAPPED UNDER INVERSION IN CENTRAL TO SOUTHERN
AREAS...YET ALSO DRIER AIR ATTEMPTING TO INFILTRATE IN FROM THE
NORTHEAST...AROUND SURFACE HIGH PRESSURE RIDGE EXTENDING THROUGH THE
GREAT LAKES. AND FINALLY...HIGHER LEVEL CLOUDS MOVING INTO THE
AREA...FROM A WEAK IMPULSE THAT WILL CAUSE A FEW FLURRIES IN THE
NORTHWEST. MVFR TO IFR EXPECTED IN VALLEYS OF THE CENTRAL LOWLANDS
TO 14Z OR SO DUE TO FOG...AS WELL AS THE TYGART AND GREENBRIER
VALLEYS. RAPID IMPROVEMENT TO VFR FOR REST OF THE DAY AFTER THAT.
IMPULSE IN NORTHWESTERN PART OF THE AREA MAY BRIEFLY DROP CIG TO
MVFR THROUGH ABOUT 17Z...BUT VIS SHOULD STAY VFR. DRIER AIR RESULTS
IN VFR FOR MOST AREAS THROUGH TONIGHT...EXCEPT LOCALIZED MVFR VIS IN
SOME VALLEYS.
AFTER 12Z THURSDAY...
SYSTEM IMPACTS AREA THURSDAY NIGHT INTO FRIDAY...WITH RAIN AND
POSSIBLE IFR. FREEZING RAIN ALSO A THREAT IN THE WV MOUNTAIN
VALLEYS...AND LOW LEVEL WIND SHEAR NOT OUT OF THE QUESTION AREAWIDE
FRIDAY MORNING.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...MDP/JMV
NEAR TERM...MDP
SHORT TERM...JMV
LONG TERM...SL/JMV
AVIATION...MDP
