Area Forecast Discussion
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000 FXUS61 KPBZ 050653 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 253 AM EDT TUE MAY 5 2015 .SYNOPSIS...
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A SLOW MOVING FRONTAL BOUNDARY WILL KEEP RAIN CHANCES IN THE FORECAST THROUGH WEDNESDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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CURRENT RADAR IMAGERY SHOWS ISOLATED TO SCATTERED SHOWERS STRETCHING FROM WEAK ECHOES OVER FAYETTE COUNTY PA WEST TO STRONGER RETURNS NEAR DAYTON OH. THIS ACTIVITY IS LOCATED ALONG AND JUST SOUTH OF THE CURRENT WEAK SURFACE FRONT...ORIENTED WITH HIGHER MOISTURE CONTENT. EXPECTING CURRENT TRENDS OF DECAYING CONVECTION TO FURTHER WEAKEN AS IT MOVES INTO THE FORECAST AREA DURING THE PRE-DAWN HOURS. BROAD FRONTAL ZONE AND DEEPER MOISTURE WILL SHIFT NORTH SOME THROUGH MIDDAY AS A WAVE CURRENTLY PRODUCING STRONG CONVECTION OVER EASTERN IOWA TRACKS ACROSS THE SOUTHERN GREAT LAKES. THIS WILL SHIFT THE FOCUS OF ANY AFTERNOON SHOWER OR THUNDERSTORM ACTIVITY NORTH AS WELL. HI-RES MODELS THAT ARE HANDLING THE CURRENT TRENDS WITH SOME SUCCESS...ARE BEARISH WHEN IT COMES TO CONVECTIVE DEVELOPMENT THIS AFTERNOON...TO THE POINT OF VERY LITTLE PRECIPITATION ACROSS THE FORECAST AREA. DONT THINK THIS IS NECESSARILY PRUDENT...GIVEN THE AVAILABILITY OF MOISTURE AND THE AT LEAST MARGINAL INSTABILITY NOTED IN THE AFTERNOON SOUNDINGS. WILL MAINTAIN CHANCE TO LIKELY POPS NORTH OF PITTSBURGH. MODEL GUIDANCE HAS TRENDED FURTHER NORTH WITH THE TRACK OF THE UPPER-LEVEL WAVE TONIGHT...AS THE RIDGE OF HIGH PRESSURE RE-BUILDS IN THE MID-WEST. MODIFICATIONS WERE MADE TO PUSH TONIGHTS RAIN CHANCES WELL NORTH OF PREVIOUS FORECAST. SOME OF OUR SOUTHERN AND WESTERN ZONES SHOULD EVEN GET SOME CLEARING HEADING INTO TONIGHT WITH THE FOCUS OF DEEPER MOISTURE SHIFTING NORTH. TAX
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY/... FRONT WILL REMAIN ACROSS THE REGION INTO WEDNESDAY BUT EXACT PLACEMENT STILL UNCERTAIN...AS WELL HAS WHERE BEST RAIN CHANCES WILL SET UP. AS UPPER LEVEL RIDGE BUILDS MID WEEK FRONT WILL BECOME MORE DIFFUSE WITH DECREASING SHOWER CHANCES WEDNESDAY. MOISTURE MAY BEGIN TO SNEAK BACK UP THE RIDGES THURSDAY WITH DEVELOPING EASTERLY FLOW AND HAVE LEFT A LOW CHANCE FOR SHOWERS IN THE RIDGES SOUTH OF THE MASON DIXON. TEMPERATURES WILL REMAIN WARM THROUGH THE PERIOD AS HEIGHTS RISE ALOFT BUT LESS SO FOR THE I-80 CORRIDOR WHERE COOL ADVECTION WILL LIMIT HIGHS TO THE LOWER 70S WEDNESDAY. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... A BROAD H5 RIDGE WILL DOMINATE THE NERN CONUS INTO THE WEEKEND. AGGRESSIVE WARM AIR ADVECTION /WITH H9 TEMPS REACHING 20-22C/ IS INDICATED IN BOTH ECMWF AND GFS DESPITE DIFFERENCES IN THE DETAILS OF THE OVERALL PATTERN EVOLUTION. WARM TEMPERATURES WITH MAXIMA IN THE 80S AND MINIMA IN THE UPPER 50S-LOWER 60S EXPECTED THROUGH THE PERIOD. THIS WARM AIR AND INCREASING LOW-LEVEL MOISTURE WILL COMBINE TO FUEL OCCASIONAL SHOWERS AND STORMS THROUGH THE EXTENDED PERIOD. ANY SUCH STORMS WILL BE TIMED WITH SUBTLE WAVES THAT ARE NOT RESOLVED PARTICULARLY WELL BY THE MODELS AT THIS TIME. THUS...POPS IN THIS FORECAST FOLLOW A GENERAL DIURNAL TREND AND ARE FOCUSED HIGHEST IN PROXIMITY TO LARGER-SCALE UPPER-LEVEL TROUGH POSITION. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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A COMPLICATED NEAR-TERM FORECAST EARLY THIS MORNING AS A BROAD FRONTAL ZONE IS HOLDING HIGHER MOISTURE CONTENT ACROSS THE FORECAST AREA. THIS HAS RESULTED IN VERY SELECT REGIONAL TERMINALS DROPPING DOWN TO VERY LOW VISIBILITIES...ALTHOUGH MOST OF OUR MAJOR TERMINALS HAVE BEEN IMMUNE THUS FAR. HAVE CURRENT VFR CONDITIONS GIVING WAY TO MVFR IN THE PRE-DAWN HOURS WITH VISIBILITY REDUCTIONS. THIS IS BY FAR THE AREA OF LEAST CONFIDENCE. ADDITIONALLY A LINE OF RESIDUAL SCATTERED SHOWERS STRETCHES FROM ZZV TO JUST SOUTH OF HLG. NOT EXPECTING MUCH FURTHER EXPANSION OR STRENGTHENING OF THESE SHOWERS...BUT IF ONE DRIFTS OVER ZZV/HLG...IT COULD LEAD TO TEMPORARY RESTRICTIONS. LATER TODAY...HAVE THIS LINE OF SHOWERS LIFTING NORTH WITH THE BROAD FRONTAL ZONE WHERE INSTABILITY THIS AFTERNOON COULD DRIVE ADDITIONAL SHOWERS/THUNDERSTORMS. HAVE INCLUDED VCTS FOR MOST TAF SITES...BUT SPATIAL EXTENT OF THUNDERSTORM ACTIVITY SHOULD BE FAIRLY LIMITED. TAX .OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/... SCATTERED RESTRICTIONS IS A POSSIBILITY EARLY WEDNESDAY AS FRONTAL BOUNDARY SLOWLY DECAYS.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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