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Area Forecast Discussion
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000
FXUS61 KPBZ 260257
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
957 PM EST TUE NOV 25 2014

.SYNOPSIS...
LOW PRESSURE SYSTEM IS EXPECTED TO DEVELOP AND RIDE NORTHWARD
ALONG THE COAST ON WEDNESDAY...BRINGING ACCUMULATING SNOW TO AREAS
SOUTH AND EAST OF PITTSBURGH. A SECOND WEAKER SYSTEM WILL USHER IN
COLDER TEMPERATURES AND LINGERING SNOW SHOWER CHANCES THROUGH THE
END OF THE WEEK.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
WITH 945PM UPDATE...HAVE SLOWED UP ARRIVAL OF SNOW BY A COUPLE OF
HOURS IN THE RIDGES CONSIDERING 00Z NAM AND 01Z HRRR SHOW A MUCH
SLOWER ARRIVAL OF PRECIPITATION IN THOSE LOCATIONS. THIS CHANGE IS
MINOR ENOUGH THAT NO CHANGES TO THE START OF ADVISORIES/WARNINGS
WAS MADE. OTHER NOTICEABLE CHANGE IN THE FORECAST WAS TO INCREASE
POPS OUTSIDE OF THE ADVISORY/WARNING AREA ON WEDNESDAY. THIS WAS
DONE TO BETTER REFLECT CONFIDENCE OF WHERE SNOWFALL WILL
OCCUR...WITH ONLY VERY MINOR CHANGES MADE TO THE INHERITED
SNOWFALL FORECAST. PREVIOUS DISCUSSION FOLLOWS.

QUIET WEATHER IN THE INTERIM AS A SURFACE LOW PRESSURE SYSTEM
BEGINS TO DEVELOP ALONG THE SOUTHEAST COAST THIS EVENING. THIS LOW
WILL THEN LIFT NORTHEASTWARD WITH THE HELP OF A DIGGING UPPER
LEVEL SHORTWAVE OVER THE PLAINS AND A STRENGTHENING UPPER LEVEL
JET....RIDING ALONG THE COLD FRONT THAT CROSSED THE REGION
YESTERDAY. TEMPERATURES WILL DROP INTO THE UPPER 20S AND LOWER
30S TONIGHT ACROSS THE REGION.

THE GENERAL MODEL CONSENSUS IS THAT SNOW WILL BEGIN TO OVERSPREAD
THE REGION EARLY TOMORROW MORNING FROM SOUTHEAST TO NORTHWEST AS
THE LOW IS LIFTED NORTHWARD. THE NAM SEEMS TO BE THE
OUTLIER...WITH VERY HIGH OMEGA VALUES AND THUS SNOWFALL
ACCUMULATIONS IN COMPARISON TO ALL OF THE OTHER MODELS...AND
SEVERAL RUNS OF THE MODELS. WITH THAT BEING SAID...THE QPF VALUES
HAVE INCREASED A BIT AMONG ALL OF THE MODELS...WHICH EVEN WITH
MODEST SNOW RATIOS LEADS TO WARNING CRITERIA SNOW IN THE HIGHER
ELEVATIONS OF GARRETT...PRESTON...AND TUCKER COUNTIES AND JUST
EXCEEDING WARNING CRITERIA IN THE CHESTNUT AND LAUREL RIDGES. A
BIT OF AN EXPANSION WESTWARD IN THE TRACK HAS ALSO LEAD TO THE
ISSUANCE OF AN ADVISORY FOR 2-4 INCHES IN THE COUNTIES IMMEDIATELY
ADJACENT TO THE WARNING...WITH LESSER AMOUNTS EXPECTED FURTHER
NORTH AND WEST.

IT IS EXPECTED THAT THE BULK OF THE SNOWFALL WILL BE OVER BY LATE
AFTERNOON AS THE SYSTEM PULLS OFF TO THE EAST. WITH WETBULBING
EXPECTED...HIGH TEMPERATURES WILL STRUGGLE TO MOVE OUT OF THE LOW
TO MID 30'S TOMORROW.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
DIGGING SHORTWAVE INTO THE WESTERN GREAT LAKES WILL BRING LIGHT SNOW 
SHOWERS EARLY THURSDAY...WITH A TRANSITION TO LAKE ENHANCED SNOW 
SHOWERS LATER THURSDAY AFTERNOON AND THURSDAY NIGHT. MODELS STILL 
PROG 850MB TEMPS TO FALL TO NEAR -10C BY THURSDAY NIGHT AND WITH A 
DECENT LAKE FETCH EXPECT SOME LIGHT ACCUMULATIONS IN THE RIDGES AND 
I-80 CORRIDOR. TEMPERATURES WILL BE AROUND 10 DEGREES BELOW SEASONAL 
AVERAGE. DRY HIGH PRESSURE WILL MOVE ACROSS THE REGION FRIDAY WITH 
CONTINUED COLD TEMPERATURES.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A STREAM OF MOISTURE FROM THE CANADIAN ROCKIES WILL KEEP CLOUDS AND 
PRECIPITATION CHANCES IN THROUGH THE WEEKEND AS NW FLOW HOLDS INTO 
EARLY SUN. HIGH PRESSURE WILL SLIDE SOUTH INTO THE NRN PLAINS OVER 
THE LATTER PART OF THE WEEKEND...DISLODGING A WEAK COLORADO LOW WITH 
RELATIVELY LOW MOISTURE INTO OUR AREA. WHILE THIS MEANS MORE LIGHT 
PRECIPITATION...THE GOOD NEWS IS A TRANSITION TO SWERLY FLOW AND 
OVERALL WARMING INTO NEXT WEEK. MODELS HAVE MADE REMARKABLE PROGRESS 
IN CONSISTENCY OVER THE LAST 24HRS LENDING TO HIGHER CONFIDENCE IN 
THE EXTENDED TRENDS.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDS ARE EXPD THIS EVE...EXCEPT FOR FKL WHERE PERSISTENT MVFR
SC IS TRAPPED UNDER A TEMPERATURE INVERSION. OTRW...EXP CONDS TO
DETERIORATE TO MVFR AND EVENTUALLY IFR FOR MOST PORTS NR AND E OF
THE OH/PA BORDER AS LOW PRES ADVNS UP THE E COAST AND SPREADS SNW
INTO THE RGN. THE SNW SHOULD EXIT LT WED AS THE MOVES FURTHER
NEWD...THOUGH MVFR CIGS ARE EXPD TO CONT.  

OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/...
PERIODIC RSTRNS ARE PSBL THRU THE WKEND WITH SVRL FAST MOVG
DISTURBANCES.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER STORM WARNING FROM 4 AM TO 6 PM EST WEDNESDAY FOR 
     MDZ001.
OH...NONE.
PA...WINTER STORM WARNING FROM 4 AM TO 6 PM EST WEDNESDAY FOR 
     PAZ074-076.
     WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM EST WEDNESDAY FOR 
     PAZ023-073-075.
WV...WINTER STORM WARNING FROM 4 AM TO 6 PM EST WEDNESDAY FOR 
     WVZ023-041.
     WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM EST WEDNESDAY FOR 
     WVZ021-022.

&&

$$







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