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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