-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 250616
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
116 AM EST WED FEB 25 2015

.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH TONIGHT WITH LIGHT SNOW SHOWERS.
BELOW AVERAGE TEMPERATURES WILL REMAIN THROUGH THE WEEK.

&&

.NEAR TERM /THROUGH TODAY/...
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APPROACHING FRONT NOW JUST NORTH AND WEST OF OHIO WITH WITH LATEST
GUIDANCE INDICATING PLACEMENT OVER EASTERN OHIO ZONES SHORTLY
BEFORE DAYBREAK AND EAST OF THE RIDGES BY LATE MORNING. GIVEN THE
LATER TIMING...HAVE INCREASED NEAR TERM TEMPERATURES...MOST
SIGNIFICANTLY ACROSS THE NE OHIO AND NW PA AS THERE WILL BE
SUFFICIENT SOUTHWESTERLY WINDS AHEAD OF THEW FRONT TO KEEP LOWER
LEVELS WELL MIXED THROUGH THE MAJORITY OF THE NIGHT. DO NOT
ANTICIPATE MUCH RECOVERY DURING THE DAY WITH WINDS SHIFTING
NORTHWEST FOLLOWING THE MORNING FRONTAL PASSAGE. PREV DISCUSSION
FOLLOWS..

A VERY DRY BOUNDARY LAYER REMAINS OVER THE
REGION THIS EVENING AFTER THE WARM DAY...SOME MOISTURE INPUT FROM
MELTING...SOUTHWESTERLY BOUNDARY LAYER FLOW...AND MID-LEVEL RH
MOISTURE INCREASING ENOUGH TO BRING SOME CLOUDS OVER THE AREA. ALL
OF THESE THINGS HAVE DONE LITTLE TO ALTER THE LOW LEVEL MOISTURE
PROFILE...EVEN WHILE TEMPERATURES ARE SITTING 25 DEGREES OR SO
WARMER THAN YESTERDAY. THIS WILL POSE A PROBLEM AS THE NEXT SYSTEM
SLIPS TOWARD OUR AREA OVERNIGHT.

AS MENTIONED...MID LEVEL RH VALUES ARE ALREADY UP...AND A FAIRLY
SHARP SHORT WAVE TROUGH AND ASSOCIATED BALLED UP VORT MAXIMA LOOK
TO MOVE ACROSS LAKE ERIE LATE THIS EVENING. DIFFERENTIAL PVA AND A
STEEPENING OF THE LOW LEVEL LAPSE RATES DUE TO COLD ADVECTION OFF
THE DECK SHOULD ALLOW FOR SUFFICIENT LIFT TO BE GENERATED TO
DEVELOP SOME SNOW SHOWERS ACROSS THE NORTHERN TIER THAT WILL BE
STRONG ENOUGH TO MOISTEN UP THE BOUNDARY LAYER. THE FARTHER YOU GO
SOUTHWARD...THE MORE PROBLEMATIC THE EQUATION BECOMES TO
GENERATING SNOW SHOWERS. WITH LIFT BEING MORE DISTANT...AND LOW
LEVEL LAPSE RATES LESS UNSTABLE...NOT TO MENTION LESS INSTABILITY
BISECTING THE LOWER REACHES OF THE DENDRITIC GROWTH ZONE...SNOW
SHOWERS WILL BE FAR LESS COMMON SOUTH OF I-80 AND ESPECIALLY SOUTH
OF THE TURNPIKE. IN REALITY...ACCUMULATING SNOW ONLY REALLY SEEMS
POSSIBLY ACROSS THE FAR NORTH. ADDITIONALLY...AS STEEPER LAPSE
RATES REACH THE RIDGES...A FEW UPSLOPE SNOW SHOWERS WITH MINIMAL
ACCUMULATIONS AGAIN SEEM LIKELY THERE BY MORNING.

DUE TO ABUNDANT CLOUDS AND WARM ADVECTION THIS EVENING...LOWS WILL
BE LEAPS AND BOUNDS WARMER THAN LAST NIGHT. HOWEVER...THESE WILL
LIKELY REMAIN WELL BELOW NORMAL.

DRIER AIR SHOULD AGAIN RETURN FOR THE DAYTIME ON WEDNESDAY...WHICH
SHOULD ALLOW FOR SOME EROSION OF THE CLOUDS. HOWEVER...THIS
CLEARING WILL LIKELY BE SHORT LIVED...AS THE NEXT COUPLET OF
SYSTEMS HEADS TOWARD THE REGION BY WEDNESDAY NIGHT AND THURSDAY.
FRIES
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&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...
COMBINATION OF SYSTEMS FOR WEDNESDAY NIGHT AND THURSDAY WITH A
NORTHERN STREAM SHORTWAVE AHEAD OF ANOTHER COLD CANADIAN SURFACE
HIGH MOVES SOUTH...WHILE A SUPPRESSED SOUTHERN STREAM WAVE SHEARS
OUT ACROSS THE MID ATLANTIC STATES. DEEP MOISTURE WILL BE LACKING
BUT DO EXPECT SNOW SHOWERS AT TIMES BEFORE DAYBREAK THURSDAY
MORNING CONTINUING THURSDAY. COLD FRONT WILL EXIT AS SURFACE HIGH
BUILDS SOUTHEAST THURSDAY NIGHT INTO FRIDAY. CONTINUED QUITE COLD
THROUGH THE PERIOD WITH LOWS NEAR OR BELOW ZERO AGAIN FOR THURSDAY
NIGHT. TEMPERATURES WILL HOLD MAINLY IN THE TEENS FRIDAY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
ONLY SIGNIFICANT CHANGES WERE TO TEMPERATURES EARLY IN THE
EXTENDED PERIOD. ARCTIC HIGH WITH CLEARING SKIES SHOULD ALLOW FOR
SIGNIFICANT RADIATIONAL COOLING FRIDAY NIGHT AND TOOK TEMPERATURES
DOWN TOWARD NEWEST WPC GUIDANCE FRIDAY NIGHT. LOWERED MAX TEMPS
FOR SATURDAY AS WELL.

PATTERN MUDDIES THEREAFTER AS MAIN BAROCLINIC ZONE SETS UP SHOP
IN OR JUST SOUTH OF OUR REGION FROM SUNDAY INTO EARLY NEXT WEEK.
MOIST SW FLOW AND A FEW SHORTWAVES WILL PROVIDE OPPORTUNITIES FOR
PRECIPITATION...THE BEST OF WHICH APPEARS TO BE SUNDAY NIGHT INTO
MONDAY AT PRESENT TIME. PRECIPITATION TYPE REMAINS UNCERTAIN
THROUGH THIS PERIOD. ENSEMBLES LIKELY WOULD PROVIDE THE PATH OF
LEAST REGRET AT THIS POINT. NEVERTHELESS...THE RISING H500 HEIGHTS
POINT TO TEMPERATURES AT LEAST GETTING WITHIN THE REALM OF
SEASONABLE VALUES BY THE END OF THE EXTENDED PERIOD. CL

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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A COLD FRONT WILL CROSS THE REGION EARLY THIS MORNING...WITH THE
BIGGEST IMPACT BEING A SEVERAL HOUR PERIOD OF MVFR CIGS. BASED ON
LATEST MODEL SOUNDINGS...CIGS SHOULD IMPROVE TO LOW VFR LEVELS BY
LATE MORNING/EARLY AFTERNOON...HOWEVER...CONFIDENCE OF THIS
OCCURRING IS ONLY ABOUT 60%. LIGHT SNOW MAY ACCOMPANY THE
FRONT...MAINLY ACROSS NORTHERN SITES...BUT IMPACTS WILL BE MINIMAL.

OUTLOOK.../WEDNESDAY THROUGH SUNDAY/...
RESTRICTIONS ARE POSSIBLE AREA WIDE WITH A LATE THURSDAY
DISTURBANCE SOUTH OF PIT. RESTRICTIONS WILL ALSO BE POSSIBLE
SUNDAY WITH AN APPROACHING COLD FRONT.
-- End Changed Discussion --

&&

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

&&

$$