Area Forecast Discussion
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000 FXUS61 KPBZ 211540 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 1140 AM EDT TUE OCT 21 2014 .SYNOPSIS... DAMP AND COOL WEATHER WILL CONTINUE UNTIL UPPER LOW PRESSURE SHIFTS EASTWARD DURING THE LATTER HALF OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... IMPRESSIVE CIRCULATION PRESENT ON CURRENT RADAR AS AN MCV FEATURE IS VERY SLOWLY MOVING W TO E ACROSS THE NRN 1/3 OF THE CWA. DESPITE ENHANCED RADAR REFLECTIVITIES ALONG THE NRN EDGE OF THE MCV CIRCULATION...THE HIGHEST RAINFALL REPORTS RECEIVED HAVE BEEN AROUND 1/3" PER HR. EXAMINATION OF THE INDIVIDUAL RADAR SLICES REVEALS THAT A GOOD PORTION OF THE ENHANCEMENT IS DUE TO BRIGHT BANDING ON THE RADAR...WITH FREEZING LEVELS RIGHT AROUND 7KFT. LATEST WATER VAPOR IMAGERY SHOWS ANOTHER SW SWINGING SOUTH THROUGH LAKE ERIE WITH AN ATTENDANT VORT MAX THROUGH OHIO. THIS IS GENERATING LAKE ENHANCED RAIN SHOWERS OVER THE SRN SHORE OF LAKE ERIE EXTENDING INTO OUR NRN CWA AND CONGEALING WITH THE BACK EDGE OF THE SLOW MOVING CIRCULATION CURRENTLY OVER THE NE CWA. THIS VORT WILL EFFECTIVELY CUT-OFF THE UPPER LOW OVER THE NEXT SEVERAL HOURS AND ALLOW IT TO DRIFT RIGHT OVERTOP OF US. WITH COPIOUS AMOUNTS OF LLVL MOISTURE AND THE COLD POOL ALOFT MAXIMIZING OVER OUR AREA NEXT SEVERAL HOURS...WOULD EXPECT FURTHER DEVELOPMENT OF CONVECTIVELY DRIVEN RAIN SHOWERS. WE ARE ALREADY BEGINNING TO SEE THIS OVER NRN WV AFTER A RELATIVELY DRY MORNING. TONIGHT THE UPPER LOW DRIFTS SOUTH OF THE AREA...ENHANCING NRLY FLOW ALOFT WRAPPING MOISTURE BACK AROUND THE SYSTEM. THE LLVL FLOW WILL REMAIN NWRLY ENABLING AN UPSLOPE COMPONENT...THUS WILL CONTINUE THE LIKELY POPS IN THE SE RIDGES. ELSEWHERE...MULTIPLE WEAK MID-LEVEL VORTS ARE PROGGED TO SWING AROUND THE PARENT LOW...AND SHOULD CONTINUE TO AID THE DEVELOPMENT OF LIGHT RAIN SHOWERS. KEEPING CHC POPS IN ACROSS MUCH OF THE CWA THROUGH WEDS MORNING. WITH TEMPS MODERATED BY CLOUD COVER AND SHOWER ACTIVITY...LARGE MODIFICATIONS WERE NOT NECESSARY. TAX && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... COLD MID LVLS WL PERSIST OVR THE REGION THROUGH WEDNESDAY DESPITE THE LOW CNTR SHIFTING TWD THE COAST. DESPITE A CONSIDERABLE REDUCTION IN POPS...SHWRS CHCS IN THE LOW THRESHOLD CONVECTIVE ENVIRONMENT WERE MAINTAINED WITH EMPHASIS OVR THE UPSLOPE AREAS ALNG THE I 80 CORRIDOR AS WELL AS THE RIDGES. THEREAFTER...WARMING ALOFT/LOWERING INVERSION IS FORECAST TO SUPPRESS PCPN CHCS ON THURSDAY...ALTHOUGH SLGT TO CHC NMBRS WERE KEPT OVR THE HIGHER ELEVATIONS IN COLLABORATION WITH NEIGHBORING WFOS. TRAILING SHRTWV IS PROGGED FOR A FRIDAY CROSSING OF THE REGION...BUT SOME CLDS ARE ALL THAT IS ANTICIPATED GIVEN THE LACK A THERMAL TROF ALOFT AS WELL AS SUFFICIENTLY DEEP MSTR. SHORT TERM TEMPS WERE TWEAKED USING BIAS CORRECTED GFS MOS TRENDS...BUT LITTLE CHANGE WAS NEEDED. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... BLDG RIDGING ACRS THE CNTRL CONUS WL SHIFT E THRU ERLY NXT WK KEEPING DRY WEA IN THE FCST. SEASONALLY COOL TEMPS ARE EXP TO PUSH ABV AVG LVLS BY ERLY NXT WK. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... A LARGE AND VERY SLOW MOVING SYSTEM IS MOVING THROUGH THE GREAT LAKES AND ACROSS THE AREA OVER THROUGH WEDS. THE MOISTURE ASSOCIATED WITH THIS SYSTEM IS FOUND PRIMARILY IN THE LOW TO MID-LEVELS WITH AN EXPANSIVE CLOUD DECK AND LIGHT RAIN SHOWERS GENERATED...THUS MVFR-IFR CONDITIONS ARE EXPECTED AREA-WIDE THROUGH MID-MORNING WEDS. AS OF 15Z MOST TERMINALS HAVE IMPROVED TO MVFR...BUT ARE EXPECTED TO DIP AGAIN INTO IFR AND POSSIBLY LIFR TONIGHT WITH REDEVELOPMENT OF LOW CIGS. TAX .AVIATION /WEDNESDAY THROUGH SATURDAY/... DUE TO THE LARGE AND SLOW MOVING UPPER LEVEL LOW PRESSURE SYSTEM...PERIODIC RSTRNS COULD LAST THROUGH THURS IN SCATTERED SHRA. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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