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Area Forecast Discussion
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000
FXUS61 KPBZ 260647
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
147 AM EST THU FEB 26 2015

.SYNOPSIS...
LIGHT SNOW SHOWERS THURSDAY WILL GIVE WAY TO DRY AND FRIGID
CONDITIONS FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
CURRENT RADAR IMAGERY SHOWING ECHOES BEGINNING TO ENCROACH THE
AREA...SEEMINGLY FROM ALL SIDES. HOWEVER...CURRENT DEWPOINT
SPREADS OF 10 TO 15 DEGREES AND A SIGNIFICANT LAYER OF DRY AIR
RECORDED ON THE 00Z UPPER AIR SOUNDING HAVE KEPT ACTUAL
PRECIPITATION AT BAY. THIS WILL MORE THAN LIKELY CONTINUE FOR
SEVERAL MORE HOURS BEFORE THE DRY AIR IS ERODED ENOUGH FOR THE
SNOW TO REACH THE GROUND. THUS...HAVE PUSHED BACK TIMING OF POPS
THIS MORNING BY A FEW HOURS.

AS THE SOUTHERN STREAM LOW PRESSURE SYSTEM GETS EJECTED FROM THE
REGION BY THE UPPER LEVEL TROF THIS MORNING...DEEPER MOISTURE WILL
SKIRT THE SOUTHEAST RIDGE ZONES. THIS WILL RESULT IN ENHANCED
CLOUD COVER AND LIGHT SNOW BANDS ENTERING THE SOUTHEASTERN PART OF
THE FORECAST AREA. BEST CHANCE OF THIS HAPPENING WILL BE FROM
ABOUT SUNRISE THROUGH MIDDAY. CLOUDS OVERSPREADING THE AREA WILL
KEEP TODAYS HIGHS IN CHECK.

AT THE SAME TIME...A RELATIVELY DRY UPPER LEVEL TROF WILL SWING
THROUGH THE SOUTHERN GREAT LAKES AND DEEPEN THE MOISTURE OVER THE
EASTERN OH AND NORTHWEST PA. ALTHOUGH THERE IS A GENERAL LACK OF
FORCING WITH THIS SYSTEM...THE MODEST LIFT WITH THE APPROACHING
700MB TROF AND DEEPER MOISTURE SHOULD BE ENOUGH TO GENERATE LIGHT
SNOW. BY EVENING THE 850MB TROF IS CLEARING THE AREA AND WIND WILL
SHIFT TO THE NORTHWEST. THIS WILL BRING IN MUCH COLDER AIR AS THE
NIGHT PROGRESSES. 

A COMBINATION OF THE STRONG COLD AIR ADVECTION AND THE PASSAGE OF
THE MID-LEVEL TROF WILL GENERATE POSSIBLY THE BEST CHANCES OF SNOW
AREA WIDE FROM LATE EVENING TO MIDNIGHT. MODEL SOUNDINGS SHOW LOW
LEVEL LAPSE RATES STEEPENING AS 850MB TEMPERATURES DROP BELOW
-15C. CONVECTIVELY DRIVEN SNOW SHOWERS WILL GENERALLY BE
LIGHT...BUT SNOW RATIOS SHOULD INCREASE AS THE COLDER AIR INVADES
THE MOISTURE SOURCE LAYER. ALL TOLD A QUICK COATING COULD FALL
THROUGH THE NIGHT...MAINLY EAST OF THE OH/WV BORDER...1-2" COULD
OCCUR IN THE MOUNTAINS OF WV/PA/MD AS RESIDENCE TIME WILL BE
LONGER. INCREASED LOWS A DEGREE OR TWO THURS NIGHT...AS THE COLDER
AIR IS A BIT SLOWER TO MOVE IN. A NORTHWEST TO SOUTHEAST GRADIENT
WILL BE PRESENT IN LOW TEMPERATURES THROUGH FRI MORNING. LOWS
SHOULD BE IN THE SINGLE DIGITS BELOW ZERO ACROSS OUR FAR
NORTHWESTERN ZONES IN OH/PA. WINDS WILL BE DIMINISHING...BUT
MARGINAL ADVISORY LEVEL WIND CHILL VALUES MAY OCCUR. CONFIDENCE IN
KEEPING WIND ABOVE 5KTS IS NOT HIGH ENOUGH AT THIS
TIME...PRECLUDING THE NEED FOR AN ADVISORY.
TAX


&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
SNOW SHOWERS WILL BE DIMINISHING WEST TO EAST THURSDAY EVENING
WITH 850MB TEMPS RANGING FROM -18 TO -20C BY 12Z FRIDAY BASED ON
THE NAM. THIS WILL PUSH TEMPERATURES INTO THE SINGLE DIGITS WITH
BELOW ZERO READING ACROSS THE NORTH. ARCTIC HIGH WILL BUILD OVER
REGION FOR FRIDAY THROUGH SATURDAY KEEPING TEMPERATURE 25 TO 30
DEGREES BELOW AVERAGE. CLEAR SKIES FRIDAY NIGHT WITH CALM WINDS
OVER SNOW WILL ALLOW FOR TEMPERATURES WELL BELOW ZERO FRIDAY NIGHT.
SURFACE RIDGE AXIS BEGINS TO PUSH EAST SATURDAY AFTERNOON
ALLOWING TEMPERATURES TO RECOVER INTO THE 20S WITH NEAR 30 FOR
THE MASON DIXON LINE.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
MINIMAL CHANGES TO THE EXTENDED WERE MADE MAINLY FOR COORDINATION
WITH SURROUNDING OFFICES. 

MARCH BEGINS WITH SFC HIGH PRESSURE BEING SHUNTED TO OUR EAST AS A
LONGWAVE TROF DIGS IN ALONG THE PACIFIC COAST. THIS WILL AT LEAST
TEMPORARILY BRING A CHANGE TO THE UPPER LEVEL FLOW TO A MORE ZONAL
REGIME. A WEST TO EAST BOUNDARY WILL SERVE AS A LOOSE FOCUS FOR
PRECIPITATION OVERSPREADING THE REGION BY LATE WEEKEND.
TEMPERATURES SUNDAY SHOULD MOVE TOWARD THE SEASONAL AVERAGE...WHICH
WILL PROVIDE A MIX OF PRECIPITATION TYPES. GIVEN THE RECENT COLD
TEMPERATURES...SFC TEMPERATURES MAY RESULT IN FREEZING RAIN BEING
INCLUDED IN FUTURE UPDATES. AT THE MOMENT...INCLUSION OF A FEW
HOURS OF FREEZING RAIN IS A BIT TOO FINE SCALE AND THUS CONFIDENCE
IS NOT HIGH ENOUGH.

LONG RANGE GUIDANCE VARIES A BIT HEADING INTO NEXT WEEK...BUT SIGNS 
POINT TO ANOTHER STORM SYSTEM FROM THE SOUTHERN STREAM MOVING EAST
MID WEEK WITH ANOTHER ROUND OF MIXED PRECIPITATION.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS ARE EXPECTED INTO EARLY MORNING AS CLOUDS INCREASE
WITH A COUPLE OF APPROACHING SHORTWAVES. ANY SNOW FROM A WAVE
CROSSING THE MID ATLANTIC REGION SHOULD STAY TO OUR SOUTH. THE
SECOND SHORTWAVE PROGGED TO ADVANCE ACROSS THE GREAT LAKES
THURSDAY AND THURSDAY EVENING SHOULD SPREAD MVFR CONDITIONS WITH
SCATTERED SNOW SHOWERS...THOUGH FKL AND DUJ ARE PROGGED TO SEE
BETTER MOISTURE AND STRONGER LIFT WHICH COULD PRODUCE IFR
VISIBILITIES BY THIS AFTERNOON. SNOW SHOWERS SHOULD DECREASE AS
SUPPORT EXITS OVERNIGHT...THOUGH MVFR CEILINGS SHOULD REMAIN.

OUTLOOK.../FRIDAY THROUGH MONDAY/... 
RESTRICTIONS ARE LIKELY WITH CROSSING LOW PRESSURE SUNDAY INTO
MONDAY.

&&

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

&&

$$






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