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Area Forecast Discussion
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000
FXUS61 KPBZ 211532
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1132 AM EDT THU AUG 21 2014

.SYNOPSIS...
UNSETTLED WEATHER WILL CONTINUE THROUGH THE WEEKEND WITH
OCCASIONAL SHOWERS AND THUNDERSTORMS.

&&

.NEAR TERM /THROUGH TONIGHT/...
SHOWERS AND THUNDERSTORMS SUPPORTED BY UPPER LEVEL WAVE IS PROGGED
TO MOVE ESE FROM WESTERN OHIO. POPS FOR THIS AFTERNOON AND EVENING
WERE MODIFIED BASED ON LATEST HI-RES GUIDANCE AS INITIALIZATION
RANKED BEST FROM MODELS. ADDED LIKELY POPS TO THE NORTH AS UPPER
WAVE PASSES THROUGH IN THE AFTERNOON WITH COVERAGE OF CONVECTION
EXPECTED TO INCREASE. VISIBLE SATELLITE IMAGERY SHOWS AMPLE CLOUD
COVERAGE ACROSS MUCH OF THE REGION. HENCE...OPTIMAL DAYTIME HEATING
WILL NOT OCCUR...HOWEVER...INCREASING MOISTURE WILL AID IN
INSTABILITY YIELDING THUNDERSTORMS...BUT TO BELOW SEVERE STATUS AS
SHEAR AND CAPE REMAIN MARGINAL.

GREATER COVERAGE OF CONVECTION IS EXPECTED TO WANE LATER IN THE
EVENING DUE TO LOSS OF HEATING. SOME SHOWERS MAY STILL LINGER
ACROSS THE AREA DUE TO THE NEARLY STATIONARY SURFACE BOUNDARY. NEXT
ROUND OF SHOWERS AND THUNDERSTORMS ARE FORECASTED TO OCCUR EARLY
MORNING FRIDAY AS THE NEXT SHORTWAVE APPROACHES.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
WEAK WARM FRONT LIFTS NORTHEAST EARLY FRI...ALLOWING COPIOUS DEEP 
MOISTURE TO SHIFT FURTHER EAST REACHING THE WRN EDGE OF THE FORECAST 
AREA BY DAYBREAK. A SFC LOW PRESSURE SYSTEM WILL SLIDE ALONG THE 
BOUNDARY FRI...SUPPORTED ALOFT BY A RELATIVELY WEAK H7-H5 SW TROF. 
SHOWERS AND THUNDERSTORMS SHOULD OVERSPREAD A MAJORITY OF THE CWA BY 
AFTERNOON. WIND PROFILES ARE SUPPORTIVE OF A FEW STRONGER STORMS 
WITH ROUGHLY 30KTS OF 0-6KM BULK SHEAR...HOWEVER...RESIDUAL CLOUD 
COVER AHEAD OF THE SYSTEM SHOULD ACT TO KEEP SFC TEMPS AND 
ULTIMATELY INSTABILITY LIMITED. 

EVEN WITH SEVERE POTENTIAL LIMITED...SHOWERS AND THUNDERSTORMS WILL 
BE ABLE TO TAP INTO A WARM AND HUMID AIR MASS WITH PWAT VALUES AT OR 
JUST ABOVE 2"...VALUES APPROACHING 2SD ABOVE THE MEAN. 
ADDITIONALLY...FREEZING LEVELS SHOULD BE NEARING 13KFT ALLOWING FOR 
IMPRESSIVE WARM CLOUD LAYER DEPTHS. MODERATE TO HEAVY RAIN SHOWERS 
COULD PRODUCE LOCAL WATER PROBLEMS...ESPECIALLY IN THOSE AREAS 
ALREADY SATURATED FROM TUES/WEDS RAINS. WILL CONTINUE TO MENTION THE 
HEAVY RAIN THREAT IN THE HWO FRI. 

TEMPS FRI WILL BE HIGHLY DEPENDENT ON TIMING OF WAVE AND RESULTANT 
CLOUD COVER AS WELL AS HOW FAR NORTHEAST THE WARM FRONT ADVANCES. 
BECAUSE OF THESE FACTORS...LARGE SPREAD EXISTS ACROSS THE MOS 
GUIDANCE. KNOCKED DOWN HIGH TEMPS FRI A DEGREE OR TWO...BUT TRIED TO 
STAY CLOSER TO THE WARMER MAV VALUES AS ANY BREAKS IN THE CLOUDS 
COULD SHOOT TEMPERATURES QUICKLY UP UNDER THE STILL POTENT AUGUST 
SUN.
TAX

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
MORE CLARITY EXISTS IN THE EXTENDED FORECAST WITH THE LATEST ROUND 
OF MODEL GUIDANCE. BY SUN THE SFC LOW FROM THE EARLY WEEKEND DEEPENS 
OVER THE PIEDMONT OF VA/NC PULLING THE DEEPER MOISTURE SOUTH WITH 
IT. IN THE MEANTIME...THE UPPER RIDGE CURRENTLY SETTING UP OVER THE 
SRN MS VALLEY WILL BUILD NORTH FURTHER WITH ITS AXIS SHIFTING EAST 
THROUGH SUN. THIS WILL WORK TO DEFLECT AN ADVANCING LOW PRESSURE 
SYSTEM WELL NORTH OF THE GREAT LAKES EARLY NEXT WEEK...RESULTING IN 
A WARMING AND DRYING TREND. TEMPERATURES SHOULD REMAIN AT OR EVEN 
JUST ABOVE AVERAGE INTO THE MIDDLE OF NEXT WEEK. 
TAX

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
STILL LOOKING AT THE BEST PRECIP CHANCES ACROSS NORTHERN WEST
VIRGINIA AND SOUTHEAST OHIO THIS AFTERNOON...LESS TO THE NORTH.
KEPT PREVAILING SHRA AT ZZV/MGW AND HAVE ONLY VCTS MENTIONED TO
THE NORTH. IFR POSSIBLE IN ANY THUNDERSTORM. SHOULD SEE A DECREASE
IN COVERAGE WITH LOSS OF HEATING DURING THE EVENING. PUT IN MVFR
FOG AT SOME LOCATIONS LATE. WILL NEED TO WATCH EASTERN OHIO LATE
TONIGHT FOR POSSIBLE INTRUSION OF MCS. ZZV WOULD HAVE THE BEST
CHANCE OF BEING AFFECTED.


OUTLOOK.../FRIDAY THROUGH MONDAY/...
SEVERAL CROSSING DISTURBANCES WILL CAUSE PERIODIC RESTRICTIONS
INTO THE WEEKEND.

&&

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

&&

$$






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