Area Forecast Discussion
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000
FXUS61 KPBZ 281707
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1207 PM EST WED JAN 28 2015

.SYNOPSIS...
CROSSING LOW PRESSURE WILL BRING A WINTRY MIX THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
NO MAJOR ALTERATIONS WERE NEEDED FOR THE EARLY AFTN AS COLD HIGH
PRES HAS FINALLY DISSIPATED THE CLDS AND FLURRIES.

RIDGE CONTINUES TO DRIFT EASTWARD TONIGHT AND WAA WILL BE ONGOING
AHEAD OF THE UPPER LEVEL SYSTEM. STILL A CHILLY NIGHT WITH CLEAR
TO PARTLY CLOUDY SKIES AND WIDESPREAD SNOW PACK. TEMPS WILL START
TO SLOWLY RISE AS DAYBREAK APPROACHES.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...

UPPER LEVEL RIDGE WILL FLATTEN LATE TONIGHT AND THURSDAY MORNING
AS SHORTWAVE TROUGH SWINGS THROUGH THE GREAT LAKES. NEXT SYSTEM
WILL SLOWLY MAKE ITS WAY ACROSS THE UPPER MIDWEST THURSDAY MORNING
REACHING WESTERN OHIO BY MIDDAY. SURFACE LOW ASSOCIATED WITH COLD
FRONT WILL REMAIN WELL NORTH OF THE REGION. PRECIPITATION WILL
INCREASE IN COVERAGE AHEAD OF THE FRONT LATE THURSDAY MORNING
THROUGH THE AFTERNOON. THIS IS WHEN THE FORECAST GETS REAL TRICKY.
WAA CONTINUES AHEAD OF BOUNDARY AS LOW LEVEL JET WILL PULL WARMER
AIR NORTHWARD. LOW AND MID-LEVEL THICKNESS QUICKLY RISE TO LEVELS
TOO WARM TO SUPPORT FROZEN PRECIP. DEPENDING ON WHICH MODEL IS
CORRECT...THIS WARMING MAY ENVELOP THE WHOLE AREA. TEMPERATURE
WILL RISE THURSDAY...BUT WITH A VERY COLD GROUND AND LARGE SNOW
PACK THE SURFACE ITSELF WILL BE SLOW TO RESPOND. THERE IS A HIGH
THREAT THURSDAY FOR A PERIOD OF ICE ACROSS ALL OF THE AREA. THE
REAL HEADACHE COMES FROM THE FACT THAT SENSORS MAY SHOW TEMPS
ABOVE 32...BUT WITH THE AFOREMENTIONED GROUND CONDITIONS...RAIN
WILL FREEZE AS IT CONTACTS THE SURFACE. WILL USE A BLEND OF THE
GFS AND NAM FOR PRECIP TYPE...BUT THE KEY WILL BE TO FIGURE OUT
THE SURFACE TEMPS...WHICH WILL BE NO EASY TASK.

COLD FRONT QUICKLY CLEARS THE AREA THURSDAY EVENING AND MUCH
COLDER AIR WILL PLUNGE BACK INTO THE REGION. LOW AND MID-LEVEL
THICKNESS QUICKLY RESPOND AND EXPECT AN ATMOSPHERE COLD ENOUGH TO
SUPPORT ALL SNOW BY 06Z FRIDAY. BY THIS TIME...MOST...IF NOT ALL
OF THE PRECIP ASSOCIATED WITH THE FRONT WILL BE TO THE EAST.
HOWEVER...WITH STRONG CAA AND THE MAIN SHORTWAVE TROUGH SWINGING
THROUGH...EXPECT SNOW SHOWERS TO CONTINUE INTO FRIDAY EVEN WITH
LOWERING INVERSIONS AND A FROZEN LAKE ERIE. SNOW GROWTH ZONES RAPIDLY
DROP FRIDAY...SO UNTIL THE LOWER LAYERS DRY OUT...THE THREAT FOR
SNOW SHOWERS WILL CONTINUE THROUGH MUCH OF THE DAY. WILL FOCUS
HIGHEST POPS ON THE RIDGES AND FAR NORTH.

EXPECT HIGH TEMPS ON FRIDAY TO OCCUR IN THE EARLY MORNING WITH A
STEADY DECLINE THROUGHOUT THE DAY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
COLD ARCTIC HIGH SHIFTS EAST INTO SATURDAY WITH SNOW SHOWERS IN
NORTHWEST FLOW FRIDAY ENDING FRIDAY NIGHT. WITH 850MB TEMPS
PROGGED NEAR -20C BY 00Z SATURDAY TEMPERATURES FRIDAY WILL BE
STEADY OR FALL. CLOUDS SHOULD BEGIN TO BREAK AS CENTER OF HIGH
MOVES INTO REGION FRIDAY NIGHT...WITH LOWS BELOW ZERO NORTH AND
SINGLE DIGITS SOUTH. IF CONDITIONS GO CLEAR AND CALM FRIDAY NIGHT
MAY GO BELOW ZERO ACROSS THE ENTIRE REGION. TEMPERATURES RECOVER
TO MAINLY THE 20S SATURDAY. A SIGNIFICANT STORM LOOKS POSSIBLE FOR
SUNDAY INTO EARLY MONDAY BEFORE ARCTIC AIR RETURNS TO START THE
WORK WEEK.

&&

.AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
HIGH PRES WL BRING VFR CONDS THRU TNGT. LOW PRES ADVNG ACRS THE GT
LKS IS EXPD TO BRING MVFR CONDS IN RAIN SHWRS THU S OF I 80...WITH
A WINTRY MIX TO THE N. PCPN SHOULD START FM LT MRNG INTO ERLY AFTN
W OF PIT...WITH A MD AFTN ARRIVAL E OF PIT. IN ADDN...A LLVL JET
SETTING UP FM OH INTO NWRN PA IS EXPD TO BRING LLWS TO ZZV THU
MRNG. WITH MXG EXPG SFC GUSTS AT FKL AND DUJ INSTEAD OF LLWS.

.OUTLOOK.../THURSDAY NIGHT THROUGH MONDAY/...
RSTRNS ARE LIKELY THRU ERLY FRI AS A CDFNT EXITS. WDSRPD RSTRNS
ARE LIKELY AGAIN WITH ADVNG LOW PRES SUN AND MON.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.

&&

$$

15/07



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