Area Forecast Discussion
Issued by NWS

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000
FXUS61 KPBZ 211148
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
748 AM EDT TUE APR 21 2015

.SYNOPSIS...
UNSEASONABLY COOL TEMPERATURES AND GUSTY WINDS CAN BE EXPECTED
THROUGH THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SHOWER WITH SOME GRAUPEL MOVING ACROSS ALLEGHENY COUNTY THIS
MORNING HAS PROMPTED AN UPDATE TO POPS EARLY ON AS AN UPPER
SHORTWAVE PIVOTS ACROSS THE REGION. ONCE THIS PASSES...A QUIET
PERIOD IS EXPECTED UNTIL BETTER MIXING AND DIURNAL HEATING OCCURS
LATER THIS MORNING. NO OTHER ADJUSTMENTS MADE AT THIS TIME.

PREV DISCUSSION FOLLOWS..
BROAD TROUGHING OVER THE EASTERN STATES WILL BECOME WELL
ESTABLISHED AS THE ASSOCIATED UPPER LOW SWINGS ACROSS THE NORTHERN
GREAT LAKES TODAY. LATEST WV IMAGERY SHOWS DRIER AIR ALREADY
WORKING IN ACROSS THE FORECAST AREA BUT EVEN THEN THE LARGE SCALE
CYCLONIC FLOW WILL FACILITATE MIXING AND A RATHER DEEP BOUNDARY
LAYER WILL SET UP TODAY. MODEL SOUNDINGS ARE ALL IN RELATIVELY
GOOD AGREEMENT WITH THIS AND SHOW THE BL EXTENDING UP TO AROUND
700MB ON AVERAGE BY THIS AFTERNOON. WITH THE TROUGH IN PLACE AND
JET SAGGING FARTHER SOUTH...WINDS ALOFT ARE MUCH STRONGER THAN
NORMAL FOR THIS TIME OF YEAR...WHICH STICKS OUT LOOKING AT NAEFS
RETURN INTERVALS WHICH SHOW 90TH PERCENTILE TO MAX VALUES THROUGH
THE WEEK...AND U COMPONENT ANOMALIES NEAR 3 STANDARD DEVIATIONS
ABOVE NORMAL. A WIND ADVISORY WAS ISSUED FOR WESTERN PORTIONS OF
THE FORECAST AREA CONSIDERING THE DEEP MIXING WILL TAP INTO THESE
WINDS (WHICH CAN CLEARLY BE SEEN VIA BUFKIT MOMENTUM TRANSFER
VALUES) AND SFC PRESSURE GRADIENTS ARE RATHER STRONG. SUSTAINED
WINDS ON AVERAGE WILL BE AROUND 25 MPH OVER THE COURSE OF THE
DAY...BUT WE COULD SEE GUSTS TWICE THAT MUCH AT TIMES...ESPECIALLY
IN THE VICINITY OF ANY HIGH- BASED SHOWERS TODAY. OPTED NOT TO
INCLUDE MENTION OF THUNDER IN THE FORECAST...BUT AN ISOLATED
LIGHTNING STRIKE HERE AND THERE WILL CERTAINLY BE POSSIBLE ALONG
WITH GRAUPEL.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
WINDS WILL BEGIN TO WIND DOWN BY LATE AFTERNOON AND INTO THE
EVENING AS THE MIXING DECREASES BUT SFC PRESSURE GRADIENTS AND A
SHORTWAVE APPROACHING FROM THE WEST SHOULD KEEP SUSTAINED WINDS
ELEVATED ENOUGH TO KEEP THINGS MODERATELY MIXED IN THE LOWER
LEVELS AND KEEP OVERNIGHT LOWS FROM DROPPING A CONSIDERABLE
AMOUNT. PRECIPITATION CHANCES AND GUSTY WINDS DURING THE AFTERNOON WILL
BE MAINTAINED THROUGH THE REMAINDER OF THE PERIOD AS MULTIPLE
SHORTWAVES MOVE ALONG THE BASE OF THE LONGWAVE TROUGH. AT THIS
TIME IT DOES NOT LOOK LIKE ADVISORY LEVEL WINDS WILL BE SEEN AGAIN
ON WEDNESDAY OR THURSDAY...BUT THIS WILL NEED TO BE WATCHED.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
GFS/ECMWF MODELS HAVE FLIP FLOPPED OVER THE LAST 24 HOURS ON WHETHER
THE SATURDAY SYSTEM WILL PASS ACROSS THE FORECAST AREA OR REMAIN TO
THE SOUTH. ECMWF NOW HAS THE MORE NORTHERN TRACK WHILE THE GFS HAS
THE SOUTHERN TRACK. SIMILAR TO YESTERDAY...ENSEMBLES SUPPORT THE
ECMWF SOLUTION...SO HAVE ADDED SOME POPS BACK INTO THE FORECAST FROM
PITTSBURGH SOUTH. TEMPERATURES WILL REMAIN BELOW NORMAL THROUGH THE
EXTENDED FORECAST...WITH SEVERAL NIGHTS OF NEAR FREEZING
TEMPERATURES.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
MID LEVEL CLOUDS ARE EXPECTED THROUGHOUT THE TAF PERIOD. BIGGEST
IMPACT THROUGH THE NEXT 24 HOURS WILL BE WINDS DURING THE AFTERNOON
HOURS. WIDESPREAD WEST-SOUTHWEST WIND GUSTS TO 35-40 KT ARE
EXPECTED...AND THESE SPEEDS MAY STILL BE CONSERVATIVE. GUSTS WILL
CONTINUE INTO THE EVENING HOURS...BUT SHOULD NOT BE AS STRONG BY
THAT TIME PERIOD. HIGH-RESOLUTION MODELS SHOW LINE OF SHOWERS
DEVELOPING ALONG A BOUNDARY THIS AFTERNOON EXTENDING FROM DUBOIS
SOUTHWEST BACK TOWARDS WHEELING...AND HAVE GONE WITH VCSH FOR MANY
LOCATIONS. MORE WIDESPREAD RAIN IS EXPECTED TO MOVE IN FOR
WEDNESDAY...WHICH HAS BEEN ADDED TO THE EXTENDED PORTION OF THE
PIT TAF.

.OUTLOOK.../WEDNESDAY THROUGH SATURDAY/... PERIODIC RESTRICTIONS
ARE POSSIBLE MUCH OF THE PERIOD MAINLY NORTH OF PIT AS THE UPPER
TROUGH PERSISTS OVER THE GREAT LAKES.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...WIND ADVISORY FROM 11 AM THIS MORNING TO 7 PM EDT THIS EVENING
     FOR OHZ039>041-048>050-057>059.
PA...WIND ADVISORY FROM 11 AM THIS MORNING TO 7 PM EDT THIS EVENING
     FOR PAZ007-013-014-020>022-029-073.
WV...WIND ADVISORY FROM 11 AM THIS MORNING TO 7 PM EDT THIS EVENING
     FOR WVZ001>003.

&&

$$



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