FXUS61 KPBZ 241126 CCA
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
626 AM EST THU DEC 24 2009
.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL APPROACH THE REGION TODAY...AND
OVERSPREAD THE REGION WITH RAIN AND THE POTENTIAL FOR FREEZING
RAIN LATE TONIGHT INTO FRIDAY. COLD AIR ON THE BACK SIDE OF THE
LOW WILL THEN BRING THE CHANCE OF SNOW SHOWERS FOR THE WEEKEND.
&&
.NEAR TERM /THROUGH TODAY/...
CLOUD COVER WILL INCREASE TODAY...WITH TEMPERATURES MODERATING
BACK ABOVE FREEZING. THE HIGHEST RIDGES WILL STILL HAVE MAXES AT
OR BELOW FREEZING...WITH A CONSIDERABLE SNOW PACK REMAINING.
&&
.SHORT TERM /TONIGHT THROUGH SATURDAY/...
MODELS CONTINUE TO SLOW THE ARRIVAL OF PRECIP FOR TONIGHT. IT
LOOKS LIKE MUCH OF THE PRECIP COULD HOLD OFF TILL THE DAY LIGHT
HOURS FRIDAY. WITH OVERNIGHT LOWS TONIGHT AT OR BELOW FREEZING
MOST LOCATIONS...EXCEPT SOUTHWEST...PRECIP IS STILL EXPECTED TO
BEGIN WITH AT LEAST A MIX OF FREEZING RAIN EASTERN TWO THIRDS OF
CWA. AS WARM AIR SURGES IN FROM THE SOUTHWEST...MOST LOCATIONS
SHOULD ONLY SEE THE POTENTIAL FOR FREEZING RAIN FOR A FEW HOURS
FRIDAY. THE EXCEPTION WILL BE THE WV/MD MOUNTAINS WHERE A FOOT PLUS
SNOW PACK WILL HELP TO KEEP THE BOUNDARY LAYER COOLER...AND THE
DURATION OF THE FREEZING RAIN LONGER. THEREFORE...WILL CONTINUE THE
WATCH WHERE IT IS...BUT HAVE PUSHED THE START TIME A FEW HOURS LATER
TO REFLECT THE LATER ARRIVAL OF THE PRECIP SHIELD.
AS COLDER AIR SWEEPS IN BEHIND THE SYSTEM THE REMAINING PRECIP
WILL CHANGE OVER TO SNOW SHOWERS FRIDAY NIGHT INTO SATURDAY. AT
THIS TIME...LIMITED SUPPORT FOR MUCH MORE THAN SCATTERED SNOW
SHOWERS FORESEEN.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
CLOSED COLD UPPER LOW COULD CONTINUE TO INDUCE COLD AIR
INSTABILITY AND LAKE ENHANCED SNOW SHOWERS ACROSS THE UPPER OHIO
VALLEY SUNDAY INTO MONDAY NIGHT UNTIL IT EXITS TO NEW ENGLAND.
SURFACE HIGH SHOULD ALLOW FOR SOME DRYING WEDNESDAY. CLOUD COVER
WILL HOLD DAYTIME TEMPERATURES DOWN TO FEW DEGREES BELOW NORMAL
THROUGH THE EXTENDED PERIOD.
&&
.AVIATION /11Z THURSDAY THROUGH MONDAY/...
MVFR/IFR STRATOCUMULUS SLOWLY NUDGING SOUTHWARD WILL BEGIN TO
RETREAT NORTH AS RIDGING AMPLIFIES ACROSS THE REGION THIS
MORNING/AFTERNOON. EXPECT ANY RESTRICTIONS TO REMAIN NORTH OF A
PIT/BVI/AGC/LBE LINE. FURTHER SOUTH...EXPECT CIRRUS TO INCREASE IN
COVERAGE THIS MORNING. VFR WILL PREVAIL FOR ALL AREAS BY LATE THIS
MORNING. MID DECK CLOUDS WILL INCREASE THIS EVENING ACROSS
OHIO...SPREADING ACROSS PA LATE EVENING/OVERNIGHT AS LOW PRESSURE
APPROACHES FROM THE SOUTHWEST. IN ADDITION...WINDS ALOFT WILL
INCREASE SIGNIFICANTLY...AND WITH SURFACE WINDS AROUND 10 KT...WILL
INCLUDE LOW LEVEL WIND SHEAR LATE THURSDAY NIGHT FOR ALL PORTS.
LOW PRESSURE WILL ENTER THE UPPER OHIO VALLEY OVERNIGHT THURSDAY
NIGHT/CHRISTMAS DAY. INITIAL PRECIP WILL LIKELY BEGIN AT ZZV
BY 09Z CHRISTMAS DAY...PIT BY 11-13Z...AND FKL/DUJ 13-15Z.
THERMAL PROFILES SUGGEST PRECIP AT ZZV/HLG/MGW WILL REMAIN
LIQUID THROUGH THE DAYLIGHT HOURS CHRISTMAS DAY. FOR PIT/BVI
AGC/LBE...FREEZING PRECIP WILL BE BRIEF AT ONSET...WITH PERHAPS
1-2 HOURS DURATION BEFORE CHANGING TO RAIN. FOR FKL/DUJ...FREEZING
PRECIP WILL LIKELY LINGER A BIT LONGER...AS LATE AS 18Z OR SO.
MVFR RESTRICTIONS WILL PREVAIL IN THE PRECIP...WITH IFR PSBL IN
THE HEAVIER ACTIVITY. AS WINDS INCREASE AT THE SURFACE CHRISTMAS DAY
TO 15-20KT WITH GUSTS TO 25-30KT...LOW LEVEL WIND SHEAR WILL
DIMINISH.
MVFR/IFR RESTRICTIONS ARE EXPECTED TO PERSIST FOR THE WEEKEND INTO
MONDAY...AS SCATTERED RAIN AND SNOW SHOWERS CHANGE OVER TO ALL
SNOW BY SATURDAY NIGHT AS COLDER AIR MOVES IN BEHIND THE EXITING
SYSTEM.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER STORM WATCH FROM LATE TONIGHT THROUGH FRIDAY AFTERNOON
FOR MDZ001.
OH...NONE.
PA...NONE.
WV...WINTER STORM WATCH FROM LATE TONIGHT THROUGH FRIDAY AFTERNOON
FOR WVZ023-041.
&&
$$
