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Area Forecast Discussion
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000
FXUS61 KPBZ 212238
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
538 PM EST SUN DEC 21 2014

.SYNOPSIS...
MIDWESTERN LOW PRESSURE WILL BRING WARMER TEMPERATURES AND RAIN TO
THE UPPER OHIO VALLEY REGION FOR THE FIRST HALF OF THE WEEK. SNOW
SHOWER CHANCES WILL COME WITH PASSAGE OF THAT SYSTEMS COLD FRONT
ON CHRISTMAS.

&&

.NEAR TERM /THROUGH MONDAY/...
WITH 530PM UPDATE...TWEAKED SKY COVERAGE AND HOURLY TEMPERATURE
TRENDS. AS QUICKLY AS LOW CLOUDS ERODE FROM THE SOUTH TO THE
NORTH...ADDITIONAL HIGH CLOUDS ALSO MOVE IN FROM THE SOUTH. ALSO
UPDATED HOURLY TEMPERATURE TRENDS AS PARTIAL CLEARING HAS ALLOWED
A SLIGHTLY QUICKER DROP OFF IN TEMPERATURES. PREVIOUS DISCUSSION
FOLLOWS.

WARM ADVECTION BEGINS IN EARNEST OVERNIGHT...BRINGING H850 TEMPS
ABOVE ZERO FOR THE SOUTHERN CWA BY 12Z MONDAY. SOME LOWER CLOUDS
COULD BE REALIZED PRIOR TO 12Z ALONG EAST-FACING SLOPES IN
GARRETT/TUCKER COUNTIES. GENERALLY LEANED TOWARDS THE WARMER
TEMPERATURE GUIDANCE FOR LOWS.

ON MONDAY...INVERTED TROUGH SETS UP ALONG THE CAROLINA COAST.  WITH 
DEPARTING HIGH ACROSS NEW ENGLAND...A COLD AIR DAMMING SCENARIO 
LOOKS TO BE SETTING UP FOR THE EAST-FACING RIDGES. FOR MOST 
AREAS...IT WILL SIMPLY BE A MOSTLY CLOUDY DAY.  BETTER
MOISTURE SPINS AROUND THE INVERTED TROUGH TOWARDS THE SOUTHEAST
CORNER OF THE CWA BEGINNING LATER MONDAY MORNING. WITH THE
OVERNIGHT WARM ADVECTION ALOFT AND COLD AIR EXPECTED TO BE TRAPPED
IN THE VALLEYS...A TEMPERATURE STRUCTURE IDEAL FOR FREEZING RAIN
WILL BE PRESENT ACROSS GARRETT/PRESTON/TUCKER COUNTIES.
HOWEVER...QPF WILL BE THE LIMITING FACTOR AS MOISTURE AND LIFT ARE
TOO SHALLOW TO SUPPORT PRECIPITATION OF ANY SIGNIFICANCE. CANNOT
JUSTIFY ANYTHING HIGHER THAN CHANCE POPS AT PRESENT. ONLY A COUPLE
HUNDREDTHS OF AN INCH OF LIQUID ARE EXPECTED AT MOST. WILL NOT BE
ISSUING ANY HEADLINES AT THE PRESENT TIME. SPS CAN BE USED IN THE
MORNING IF THE THREAT INCREASES. CONTINUED WARM ADVECTION WEST OF
THE RIDGES WILL PUSH MONDAY HIGH TEMPS AT LEAST SEVERAL DEGREES
ABOVE NORMAL...WHILE TEMPS REMAIN IN THE 30S ALONG THE EASTERN CWA
BORDER.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
UPPER TROUGH WILL AMPLIFY AND SLOWLY PIVOT EASTWARD DURING THIS TIME 
FRAME...BECOMING MORE NEGATIVELY TILTED WITH THE HELP OF A 
STRENGTHENING UPPER LEVEL JET BY LATE WEDNESDAY. EARLY ON...THERE 
STILL REMAINS SOME UNCERTAINTY IN REGARD TO THE AMOUNT OF PRECIP 
THAT WE WILL SEE ON TUESDAY...AS WE WILL BE PARKED IN BETWEEN THE 
BETTER MOISTURE FROM THE WEAK COASTAL SYSTEM...AND THE DEEPENING 
MOISTURE ASSOCIATED WITH THE COLD FRONT TO OUR WEST. IN 
ADDITION...S-SE WIND SHOULD HELP PROVIDE SOME DOWNSLOPING AND DRYING 
JUST EAST OF THE RIDGES IN PA/WV. WITH THIS IN MIND...OPTED TO STAY 
WITH THE CHANCE POPS FOR THE DAY TUESDAY. WILL INCREASE POPS 
OVERNIGHT AS THE LOW LEVEL JET STRENGTHS AND HELPS TO PULL MOISTURE 
FROM THE GULF NORTHWARD. WITH THE NEARLY NORTHWARD PROGRESSION OF 
THE DEVELOPING SURFACE LOW...BOTH THE ECMWF AND GFS SUGGEST THE BULK 
OF THE HEAVIEST RAIN WILL STAY JUST WEST OF THE FORECAST AREA...WITH 
THE BEST CHANCE FOR MODERATE RAIN TO BE AS THE COLD FRONT CROSSES 
WEDNESDAY NIGHT. THIS SHOULD LIMIT ANY FLOOD THREAT FOR THE PERIOD.

STRONG WARM ADVECTION WILL BE ONGOING THROUGH THE ENTIRE TIME
PERIOD. EVEN WITH CLOUD COVER...HIGH TEMPERATURES ON BOTH TUESDAY
AND WEDNESDAY SHOULD BE WELL ABOVE SEASONAL VALUES WITH HIGHS
LIKELY TO REACH THE MID 50'S.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
CDFNT PASSAGE WILL INITIATE SNOW SHOWER CHANCES ON CHRISTMAS...BUT
LACK OF DEPTH TO THE COLD LYR...DRY ADVCTN IN THE MID LVLS ON THE
SRN PERIMETER OF NWD DIGGING UPR LOW...AND RAPIDLY ENSUING WARM
ADVCTN WL ENSURE A LACK OF SNOW COVER FOR CHRISTMAS.

THE RMNDR OF THE LONG TERM PD IS PROGGED TO FEATURE SEASONAL TEMPS
WITH A LATE WEEK COOLING TREND AS MDLS PROG A REAMPLIFYING FLOW
PTN WITH ERN CONUS TROFFG.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
GENL IMPROVEMENT TO VFR FOR ALL TAF SITES CAN BE EXPECTED FOR THE
TAF PD AS SLY FLOW ALOFT INTENSIFIES OVR LINGER SFC HIGH PRES.

OUTLOOK.../MONDAY THROUGH FRIDAY/...
MIDWRN LOW PRES WL SPREAD RAIN AND RESTRICTIONS OVR AREA PORTS ON
TUESDAY AND WEDNESDAY. IMPROVEMENTS ARE EXPECTED TO BE INITIATED
LTR ON THURSDAY WITH DRY SHRTWV RIDGING.

&&

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

&&

$$






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