Area Forecast Discussion
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000
FXUS61 KPBZ 111021
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
521 AM EST THU FEB 11 2016

.SYNOPSIS...
SNOW SHOWERS WILL GRADUALLY DIMINISH THURSDAY. TEMPERATURES WILL
CONTINUE TO FALL THROUGH THE WEEK WITH BITTER COLD TO START THE
WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
UNSTABLE NORTHWESTERLY FLOW HAS BEGUN TO BE OVERCOME BY DRY
CANADIAN AIR ADVECTING IN FROM THE NORTHWEST. THE PREVIOUS
SNOW SQUALL ACTIVITY THAT WAS LARGELY SITUATED ALONG A LOW LEVEL
DEFORMATION AXIS HAS LARGELY DISSIPATED AND BECOME MORE CELLULAR
AS FLOW HAS BECOME MORE UNI-DIRECATIONAL EARLY THIS MORNING. GOING
FORWARD...THE ONLY PLACE WHERE THIS MAY NOT ENTIRELY BE THE CASE
OUTSIDE THE RIDGES IS IN FOREST AND VENANGO COUNTIES. HIGH
RESOLUTION GUIDANCE SUGGESTS BANDING FROM LAKE HURON WILL TREND
SOUTHWARD LATE THIS MORNING. THIS WOULD ALLOW FOR A MULTI-LAKE
FETCH TO BRING SNOW SHOWERS FROM LAKE HURON...ACROSS LAKE
ERIE...AND INTO THE FAR NORTHEASTERN REACHES OF THE CWA. THUS POPS
AND THE WINTER WEATHER ADVISORY WILL LIKELY BE MAINTAINED HERE TO
ASCERTAIN WHETHER THIS DEVELOPMENT DOES OCCUR.

IN THE RIDGES...VISIBILITIES HAVE CONTINUED TO GENERALLY BE
BETWEEN 1 AND 2 MILES THROUGH THE NIGHT AND INTO EARLY THIS
MORNING. A PERIOD OF A ENHANCED SNOW SHOWER ACTIVITY WILL BE
LIKELY AS FLOW TURNS TO THE NORTHWEST...HOWEVER WEAKENING
SATURATION WILL MEAN LESS EFFICIENT SNOW GENERATION BY AFTERNOON.
THUS A FEW MORE INCHES WILL BE POSSIBLE IN THE RIDGES...HOWEVER
TRENDS BY AFTERNOON SHOULD ALLOW FOR SNOW SHOWER ACTIVITY TO TAPER
OFF.

ELSEWHERE...SCATTERED SNOW SHOWERS WILL BE PRESENT...HOWEVER
ACCUMULATIONS SHOULD BE LIGHT/LOCAL AS DRIER AIR MOVES INTO THE
AREA. IN FACT...GOING INTO THE NIGHTTIME TONIGHT...LOW LEVEL FLOW
STARTS TO WEAKEN CONSIDERABLY AND TURN A BIT TO THE SOUTHWEST.
THIS WILL LIKELY ERADICATE BOUNDARY LAYER RH VALUES...AND ALLOW
FOR DECENT TEMPERATURE FALLS. THEY WILL LIKELY BE TEMPERED BY
MORNING AS MID AND HIGH CLOUDS INCREASE...HOWEVER SINGLE DIGITS
WILL LIKELY STILL BE COMMON WITH WIND CHILLS INCREMENTALLY BELOW
ZERO. FRIES

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
FRIDAY BEGINS DRY AND COLD AS HIGH PRESSURE TEMPORARILY CUTS OFF
THE SNOW PRODUCTION. DEEP NORTHWESTERLY FLOW KEEPS THE DOOR TO
COLDER AIR WIDE OPEN...SO HIGH TEMPERATURES WILL REMAIN WELL BELOW
AVERAGE.

MULTIPLE UPPER-LEVEL SHORTWAVES WILL SLIDE OUT OF THE NORTHERN
PLAINS...PASSING THROUGH THE BASE OF THE PINWHEELING VORTEX IN
CANADA. THE FIRST WEAKER WAVE WILL DIVE TO OUR SOUTH ON THE FRONT
OF THE UPPER-LEVEL JET STREAK. THIS WILL BRING LITTLE MORE THAN
INCREASED CLOUD COVER AND PERHAPS A FEW LIGHT SNOW SHOWERS THROUGH
MIDDAY FRIDAY. A MORE POTENT WAVE WILL THEN DROP SOUTH THROUGH THE
WESTERN GREAT LAKES...RE-INVIGORATING SNOW SHOWERS ALONG AND AHEAD
OF THE COLD FRONT. MODERATE TO HEAVY SNOW SQUALLS AGAIN LOOK
POSSIBLE AS THE FRONT PASSES FRIDAY NIGHT. LARGELY LEFT SNOW
TOTALS INTACT FROM THE PREVIOUS FORECAST...WHICH LOOKS TO BE BELOW
ADVISORY CRITERIA FOR A MAJORITY OF THE FORECAST AREA.

ALONG WITH THE POTENTIAL FOR SCATTERED MODERATE SNOW BANDS...WINDS
WILL BE INCREASING FRIDAY NIGHT AS THE PRESSURE GRADIENT TIGHTENS
IN THE BASE OF THE LOW. SUSTAINED WINDS GREATER THAN 10KTS...AND
TEMPERATURES DROPPING INTO THE SINGLE DIGITS BY SATURDAY MORNING WILL
LIKELY NECESSITATE WIND CHILL ADVISORIES AT LEAST FOR THE RIDGES
AND ALONG THE NORTH.

SNOW SHOULD TAPER DOWN ACROSS THE WEST SATURDAY MORNING AS THE
AXIS OF THE TROUGH SHIFTS TO OUR EAST. HOWEVER...WITH VERY COLD
AIR PASSING OVER THE STILL UNFROZEN WATERS OF THE GREAT
LAKES...ADDITIONAL LAKE-EFFECT SNOW SHOWERS ARE POSSIBLE. MODEL
GUIDANCE SHOWING NORTH-NORTHWESTERLY FLOW SETTING UP AN AREA OF
CONVERGENCE DOWN WIND OF LAKE ERIE. WITH A FAVORABLE HURON-TO-
ERIE CONNECTION...LAKE-EFFECT SNOW SHOWERS SHOULD PERSIST ACROSS
OUR NORTH THROUGH SATURDAY AFTERNOON. LEFT SNOW TOTALS ASSOCIATED
WITH THIS ACTIVITY BROAD AND ON THE LIGHT SIDE...WITH HOPES FUTURE
MODEL RUNS WILL BETTER RESOLVE THE SNOW BAND LOCATION.

THE NORTH-NORTHWESTERLY FLOW WILL CONTINUE THE BARRAGE OF ARCTIC
AIR INTO OUR REGION SATURDAY...WITH A LOW CELLING FOR HIGH TEMPS
EXPECTED. MANY LOCATIONS MAY NOT GET OUT OF THE SINGLE DIGITS
ALL DAY SATURDAY. WIND CHILL ADVISORIES WILL AGAIN BE LIKELY
HEADING INTO SATURDAY NIGHT/SUNDAY MORNING...EVEN AS THE WINDS
SLACKEN.
TAX

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
SUNDAY WILL BEGIN DRY AS SURFACE HIGH PRESSURE WILL AGAIN MAKE A
TEMPORARY VISIT TO THE REGION. MODELS STILL HAVING SOME
DIFFICULTY WITH THE NEXT DISTURBANCE MOVING IN SUNDAY NIGHT.
TIMING IS NOW FAIRLY CONSISTENT ACROSS THE GUIDANCE...BUT THE
ECMWF QUICKLY WEAKENS THE WAVE UPON ARRIVAL. STILL...EXPECTING
AT LEAST A CHANCE OF LIGHT SNOW MONDAY.

MODELS NOW SHOW ANOTHER DEEPER WAVE IN THE WAKE OF THE MONDAY
SYSTEM. THIS COULD POTENTIALLY BRING ACCUMULATING SNOW BACK INTO
THE EASTERN FRINGE OF THE FORECAST AREA BY EARLY TUESDAY. WILL
NEED SEVERAL MORE MODEL CYCLE TO SORT OUT THOSE DETAILS.
TEMPERATURES WILL BEGIN TO MODERATE BY MIDDLE OF NEXT WEEK.
TAX

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
SNOW SQUALLS WILL LIKELY REMAIN BETWEEN KBVI AND KFKL THROUGH THE
MORNING BEFORE DISSIPATING. LOCAL SNOW SHOWERS WILL BE POSSIBLE AT
MOST SITES...HOWEVER NO HEAVIER SNOW SHOWERS SHOULD AFFECT ANY
SITE. CIGS WILL SLOWLY IMPROVE THROUGH THE DAY...WITH VFR
CONDITIONS LIKELY AT MOST SITES BY TONIGHT

.OUTLOOK.../THURSDAY NIGHT THROUGH MONDAY/...
OCCASIONAL RESTRICTIONS ARE EXPECTED THROUGH THE PERIOD UNDER
COLD UPPER-LEVEL TROUGHING. WHILE THURSDAY NIGHT AND SUNDAY
SHOULD BE GENERALLY DRY...SCATTERED TO WIDESPREAD SNOW SHOWERS ARE
EXPECTED FRIDAY...SATURDAY...AND MONDAY.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR MDZ001.
OH...NONE.
PA...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR PAZ008-
     009-074-076.
WV...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
     WVZ510>514.

&&

$$


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