Area Forecast Discussion
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000 FXUS61 KPBZ 211031 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 631 AM EDT THU AUG 21 2014 .SYNOPSIS... OCCASIONAL SHOWERS AND THUNDERSTORMS CAN BE EXPECTED THROUGH THE WEEKEND AS A SERIES OF DISTURBANCES MOVE THROUGH THE REGION. && .NEAR TERM /THROUGH TONIGHT/...
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630 AM UPDATE...STILL A COUPLE OF STUBBORN SHOWERS IN FAYETTE COUNTY TO DEAL WITH. OTHERWISE...LOOKING AT UPSTREAM ACTIVITY IN IN/OH THAT MAY GET INTO CWA PRIOR TO NOON. AREA OF AC IN OHIO NECESSITATED UPDATING THE SKY GRIDS AS WELL. PREVIOUS DISCUSSION... ISOLATED SHRA FINALLY EXITING THE EASTERN CWA BORDER ALONG WITH VORT MAX. FOG BEING HELD IN CHECK A BIT BY MIXING AT THE TOP OF THE BOUNDARY LAYER. STILL THINK PATCHY DENSE FOG IS POSSIBLE... ESPECIALLY IN VALLEYS...GIVEN THE WET GROUND AND MOSTLY CLEAR SKIES. FRONTAL BOUNDARY WILL CONTINUE TO HANG AROUND THE CWA TODAY AND TONIGHT...ALTHOUGH IT WILL GET A SLIGHT NORTHWARD PUSH LATER IN THIS PERIOD. DEEPER MOISTURE MAKES A RUN BACK TO THE EAST...WITH THE 1.5 INCH PWAT LINE GETTING CLOSE TO PIT THIS AFTERNOON. EXPECT SOME POCKETS OF UP TO 2500 J/KG OF CAPE TO DEVELOP...WHICH WILL ONCE AGAIN ALLOW FOR DIURNAL STORM DEVELOPMENT. 0-6KM BULK SHEAR OF 30-40 KNOTS MAY BE JUST ENOUGH TO ALLOW FOR SOME STRONG TO MARGINALLY SEVERE STORMS...ALTHOUGH ORGANIZATION WILL REMAIN LOW. EXPECTING HIGHER COVERAGE ALONG/SOUTH OF BOUNDARY WITH THE JUICIER AIRMASS...AND HAVE THE LIKELY POPS TARGETED IN THIS AREA. CHANCE POPS ARE FORECAST IN THE FKL/DUJ FAR NORTHERN REGION. DESPITE ALL THIS...AM NOT SOLD ENOUGH ON THREAT OF HEAVY RAINFALL/FLOODING TO HOIST ANY FLOOD WATCHES. BEST ORGANIZATION AND RAINFALL POTENTIAL WILL LIE OFF TO THE SOUTH AND WEST...WHERE ISENTROPIC UPGLIDE ALONG WITH H250 UPPER DIVERGENCE IN RRQ OF MODEST JET WILL ALLOW FOR ENHANCED LIFT...NOT TO MENTION THE 2 INCH PLUS PWAT VALUES. THINK THE WET AREAS IN EASTERN OHIO WILL BE ABLE TO ESCAPE ANY FURTHER IMPACTS TODAY. TONIGHT...ACTIVITY WILL DIURNALLY DECREASE AND CLOUDS WILL BREAK SOMEWHAT. CANNOT RULE OUT A SHOWER ANYWHERE OVERNIGHT THOUGH GIVEN THE AIRMASS AND FRONT. THERE ARE HINTS IN THE MODELS THAT SOME SORT OF CONVECTIVE CLUSTER/MCS MAY ATTEMPT TO FORM AND RIDE THROUGH THE OHIO VALLEY. AGAIN...EXPECT THIS TO BE MAINLY OFF TO THE SOUTHWEST...BUT COULD SEE THE ZZV VICINITY GET CLIPPED AROUND 12Z. WILL NEED TO KEEP AN EYE ON THIS. NEAR OR SLIGHTLY ABOVE NORMAL TEMPS CONTINUE TO BE FORECAST.
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&& .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 /12Z THURSDAY THROUGH MONDAY/...
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A FEW ISOLATED SHRA CONTINUED OVERNIGHT. MOST LOCATIONS ARE VFR OUTSIDE OF FKL/DUJ. BOUNDARY LAYER REMAINED A LITTLE MORE MIXED THAN EXPECTED OVERNIGHT...RESULTING IN LESS FOG. VFR CONDITIONS ARE FORECAST FOR THE BALANCE OF THE MORNING ONCE WHATEVER FOG THERE IS LIFTS. 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.../THURSDAY THROUGH SUNDAY/... SEVERAL CROSSING DISTURBANCES WILL CAUSE PERIODIC RESTRICTIONS INTO THE WEEKEND.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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