Area Forecast Discussion
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000
FXUS61 KPBZ 262314
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
614 PM EST FRI DEC 26 2014

.SYNOPSIS...
HIGH PRESSURE THROUGH SATURDAY WITH DRY AND MILD CONDITIONS. A COLD FRONT
WILL BRING THE NEXT CHANCE OF RAIN SATURDAY NIGHT AND SUNDAY.

&&

.NEAR TERM /THROUGH SATURDAY/...
HIGH CLOUDS ARE QUICKLY ADVANCING INTO THE CWA THIS EVENING AS MID
AND UPPER LEVEL RH VALUES START TO WANDER NORTHWARD.
HOWEVER...UNDER THOSE LAYERS...FAIRLY DRY AIR REMAINS FIRMLY
ENTRENCHED. ADDITIONALLY...WITH THE INVERTED TEMPERATURE
PROFILES...RH VALUES ALONG THE RIDGETOPS CONTINUE TO BE WELL BELOW
THOSE IN THE LOWER ELEVATIONS OF THE CWA. THAT SAID...MID AND HIGH
CLOUDS ADVANCING NORTHWARD SHOULD PUT A LID ON HUGE TEMPERATURE
FALLS TONIGHT. WHILE STATISTICAL GUIDANCE SUGGESTS MUCH OF THE CWA
SHOULD CHALLENGE FREEZING WITH LOWER 20S IN THE RIDGES...THIS
MAKES NO METEOROLOGICAL SENSE. INVERTED PROFILES SHOULD ALLOW FOR
MID-SLOPES AND RIDGES TO BE WARMER THAN THE VALLEYS THROUGH THE
NIGHT...PARTICULARLY AS 850 MB TEMPERATURES REMAIN AROUND +4 TO
+5C. WITH THAT SAID...LOW TEMPERATURES WERE ADJUSTED UPWARD MOST
EVERYWHERE...PARTICULARLY OVER OHIO AND IN THE HIGHER ELEVATIONS.
CLOUD EXPECTATIONS WERE LIKEWISE INCREASED SUBSTANTIALLY THROUGH
THE EVENING. FRIES

PREVIOUS DISCUSSION FOLLOWS FOR SATURDAY...
EXPECTING ANOTHER MOSTLY SUNNY DAY SAT WITH HIGHS WELL ABOVE AVG
UNDER STRONG WAA AHEAD OF THE NEXT COLD FRONT. H85 TEMPS IN THE
5-8C RANGE WILL ENGULF THE AREA WITH MIXING FROM MODEST SRLY FLOW.
A DECENT 40+KT JET WILL SKIRT OUR NWRN PERIPHERY SAT
AFTERNOON/EVENING...BUT A STOUT H9 INVERSION WILL HOLD MOST OF
THAT WIND BACK. COULD SEE A FEW LOCATIONS...ESPECIALLY
NORTH...GUST NEAR 20KTS. TAX

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
HIGH PRESSURE BECOMES DISLODGED AND PUSHED OFFSHORE FROM THE
MID-ATLANTIC SAT NIGHT AS A LOW PRESSURE SYSTEM MOVES THROUGH THE
WRN GREAT LAKES. BY LATE SAT NIGHT...MOISTURE FROM ANOTHER LOW
PRESSURE SYSTEM NEAR THE LOWER MS VALLEY WILL MOVE NORTHWARD ALONG A
SHARED BOUNDARY. THIS RELATIVELY WEAK BOUNDARY WILL APPROACH OUR WRN
PERIPHERY AS A COLD FRONT LATE SAT NIGHT INTO EARLY SUN MORNING.
RAIN SHOWERS WILL OVERSPREAD THE FORECAST AREA INTO THE DAY
SUN...ALTHOUGH WITH LIMITED MOISTURE ALONG THE WEAK
FRONT...PRECIPITATION IS EXPECTED TO BE LIGHT.

FRONTAL PROGRESS SLOWS AS IT GETS STRETCHED OUT AND BECOMES PARALLEL
TO THE MIDLEVEL FLOW.  HOWEVER...A FRESH WAVE WILL RIDE
NORTHEASTWARD ALONG THE BOUNDARY DURING THE DAY ON SUNDAY...KEEPING
PRECIPITATION IN THE FORECAST.  BEST SUPPORT/MOISTURE CLIPS THE
SOUTHEASTERN CORNER OF THE CWA..AND KEPT CATEGORICAL POPS HERE.
BEHIND THE FRONT SUNDAY NIGHT...COLDER AIR SAGS IN SLOWLY ON INITIAL
WESTERLY FLOW.  EXPECT MOST AREAS WILL SEE PRECIPITATION END BEFORE
ANY MEANINGFUL CHANGEOVER TO SNOW.  A FEW SHOWERS WILL LINGER ON
MONDAY IN THE SOUTHEAST CWA AS THE BOUNDARY FINALLY PULLS
AWAY...WHILE DRY WEATHER AND SOME CLOUDS LINGER FOR THE BULK OF THE
AREA.  WHILE PRECIP ENDS IN THE SOUTHEAST MONDAY NIGHT...ANOTHER
VERY WEAK BOUNDARY MAY TRY TO SAG INTO THE NORTHERN COUNTIES THROUGH
TUESDAY.  AGAIN...MOISTURE AND SUPPORT WILL BE VERY LIMITED AND
ELECTED TO MAINTAIN SLIGHT CHANCE POPS HERE.

AFTER ABOVE NORMAL TEMPERATURES CONTINUE SUNDAY AND SUNDAY
NIGHT...MORE SEASONABLE VALUES RETURN MONDAY AND CONTINUE THEREAFTER.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
THE EXTENDED WILL LARGELY BE DRY WITH A DECREASING TREND IN
TEMPERATURES AS A BROAD TROUGH IN THE LONGWAVE PATTERN SLOWLY SAGS
SOUTH ACROSS THE EASTERN CONUS. THERE IS A SLIGHT CHANCE OF LIGHT SNOW
SHOWERS ASSOCIATED WITH A SHORTWAVE TRANSITIONING THROUGH THE FLOW
DEVELOP MAINLY ALONG AND NORTH OF INTERSTATE 80 DURING THE MIDDLE
OF THE WEEK...BUT MOISTURE APPEARS TO BE QUITE LIMITED. FURTHER
OUT...AN AREA OF LOW PRESSURE PREVIOUSLY CLOSED OFF OVER THE
SOUTHWEST WILL EVENTUALLY IMPACT THE REGION...BUT MODELS VARY
WIDELY IN TIMING OF THIS FEATURE...BY A MARGIN OF SEVERAL DAYS.

&&

.AVIATION /23Z FRIDAY THROUGH WEDNESDAY/...
VFR WILL PREVAIL UNDER HIGH PRESSURE THROUGH THE TAF PERIOD. COULD
SEE SOME MID-LVL CLOUDS WITH A PASSING WEAK WAVE EARLY SAT...BUT
NO RESTRICTIONS ARE EXPECTED UNTIL THE ARRIVAL OF THE FRONT SAT
NIGHT. LIGHT SRLY WINDS THROUGH EARLY SAT WILL INCREASE SAT MIDDAY AHEAD
OF THE FRONT.
TAX

OUTLOOK.../SATURDAY THROUGH WEDNESDAY/...
RESTICTIONS POSSIBLE WITH THE COLD FRONT SUNDAY AND THEN AGAIN
WITH A PASSING WAVE ACROSS OUR SOUTH SUNDAY NIGHT.

&&

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

&&

$$





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