Area Forecast Discussion
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000
FXUS61 KPBZ 230512
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1212 AM EST TUE DEC 23 2014

.SYNOPSIS...
LOW PRESSURE IN THE MIDWESTERN STATES WILL BRING WARMER
TEMPERATURES AND RAIN TO THE REGION TUESDAY NIGHT AND WEDNESDAY.
GUSTY WINDS WILL ACCOMPANY THE PASSAGE OF A COLD FRONT ON
CHRISTMAS DAY.

&&

.NEAR TERM /THROUGH TODAY/...
THE FRZG RAIN ADVY WL CONT AS IS IN GARRETT UNTIL 09Z. TEMPS
REFUSE TO RISE THERE AND FREEZING DRIZZLE IS LIKELY ON GOING. MADE
MINOR TWEAKS TO TEMPS AND POPS OVERNIGHT USING LATEST HIRES MODEL
DATA.

PREVIOUS DISC...EXPECT CLOUD COVER TO GRADUALLY REFILL IN
WARM...MOIST ADVCTN ON THE ERN FLANK OF MIDWRN LOW PRES. THAT
PROCESS WL RETARD THE DIURNAL TEMP TREND AND LOWS ABOUT 5 TO 10
DEGREES ABOVE THE AVGS WERE FORECAST USING BIAS CORRECTED MOS.

MOST OF THE MODEL GUIDANCE SUGGESTS THAT TUESDAY WILL REMAIN A
RELATIVELY BENIGN DAY AS A SHORTWAVE DIGGING THE UPPER TROUGH
STRENGTHENS THE SOUTHERLY FLOW AND WARM ADVECTION OVER THE REGION.
EXPECT TEMPERATURES TO BE CLOSE TO 15 DEGREES ABOVE SEASONAL
VALUES. THE BULK OF THE PRECIP DOES NOT LOOK TO PUSH INTO THE
REGION UNTIL LATER IN THE PERIOD...SO CHANCE POPS WERE MAINTAINED
DURING THE DAY TUESDAY.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
SHARPLY-AMPLIFIED UPR TROF OVER THE MIDWRN STATES WILL LIFT INTO
THE GRTLKS RGN TUE NGT THRU WED. AHEAD OF THIS WAVE...STRONG WARM
AND MOIST SLY FLOW WILL BE MAINTAINED...PROVIDING OPPORTUNITY FOR
WDSPRD RAIN AND INCRG WARMTH. TEMPS ON WED HAVE A GOOD LIKELIHOOD
OF REACHING AT LEAST LWR 60S...LMTD PRIMARILY BY CLD CVR AND PCPN.

IT APPEARS RAIN MAY OCCUR IN TWO WAVES. FIRST WAVE WILL DVLP TUE
NGT INTO WED MRNG AS WARM AIR ADVCTN INCRS CONSIDERABLY AHEAD OF
APRCHG UPR WAVE. SECOND WAVE MAY OCCUR LATER WED AFTN AS PRE-
FRONTAL SFC TROF MOVES ACRS WARM SECTOR. AS A RESULT...TWO
RELATIVE MAXIMA IN POPS WERE INTRODUCED DURG TUE NGT-WED NGT PD.

PRIOR TO PASSAGE OF CDFNT EARLY THU MRNG...RGN WILL BE LOCATED IN
DRY SLOT OF UPR SYSTEM. LOCAL RESEARCH SUGGESTS THIS PATTERN MAY
BE FAVORABLE FOR STRONG WIND CONCERNS WED NGT IN ALL AREAS AND
SPCLY THU IN THE HIGHER TERRAIN. THIS THREAT WAS INCLD IN THE
HAZARDOUS WX OUTLOOK.

CDFNT WILL CROSS THE RGN EARLY THU MRNG. MAXIMA LKLY WILL BE
REACHED EARLY IN THE DAY...WITH COLD AIR ADVCTN DOMINATING DURG
THE DAY. CHCS FOR SNOW SHWRS WILL INCR WITH PASSAGE OF COLD POOL
ALOFT AS INSTBY INCRS AMID STEEP LOW-LVL LAPSE RATES. FETCH WILL
NOT BE FAVORABLE FOR LAKE ENHANCEMENTS EXCEPT PERHAPS IN FAR NRN
ZONES...SO NO SGFNT ACCUMS XPCD. SNOW SHWRS MAY CONT IN HIGHER
TERRAIN OF PA/MD/WV INTO THU EVE BUT WILL WANE QUICKLY AS
INVERSION HEIGHTS LWR.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
MINIMAL CHANGES WERE MADE TO THE EXTENDED AS LATEST GUIDANCE
SHOWED BOTH POOR AGREEMENT AND CONTINUITY...AND ANY CHANGES THAT
WERE MADE WERE PRIMARILY BASED ON ENSEMBLE MEANS. WITH THAT...DRY
CONDITIONS AND TEMPERATURES APPROXIMATELY 10 DEGREES ABOVE NORMAL
ARE FORECAST ON FRIDAY AS RIDGING TRANSITIONS OVER THE REGION. A
TROUGH OF LOW PRESSURE WILL THEN RESULT IN UNSETTLED CONDITIONS
SATURDAY AND SUNDAY.

&&

.AVIATION /05Z TUESDAY THROUGH SATURDAY/...
VFR CAN BE EXPECTED THROUGH MUCH OF THE NGT...WITH DETERIORATION TO
MVFR THEREAFTER AS WARM FRONT SURGES NWD.  AS THAT FEATURE
PROGRESSES...LOW END VFR SHOULD RTN UNTIL RAIN AND RESTRICTION CHCS
INCRS ON TUESDAY NGT.

OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/...
THE SYSTEMS CDFNT WL CONT RESTRICTION POTENTIAL INTO THURSDAY.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...FREEZING RAIN ADVISORY UNTIL 4 AM EST EARLY THIS MORNING FOR
     MDZ001.
OH...NONE.
PA...NONE.
WV...NONE.

&&

$$





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