Area Forecast Discussion
Issued by NWS

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000 FXUS61 KPBZ 212225 AAA AFDPBZ AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PITTSBURGH PA 625 PM 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 WEDNESDAY/...
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630PM UPDATE...POPS WERE MODIFIED WITH A COMBINATION OF LATEST RADAR PICS AND INCOMING MODEL GUIDANCE. SHOWER ACTIVITY WILL CONTINUE TO DRIFT TOWARD THE SOUTH WITH SHORTWAVE ROTATING AROUND 50H LOW. TEMPS HAVE ALSO BEEN ADJUSTED WITH LATEST LAMP NUMBERS. PREVIOUS DISCUSSION... IMPRESSIVE CIRCULATION PRESENT ON CURRENT RADAR AS A DECAYING LOW- TOPPED MCV HAS STALLED NEAR JEFFERSON COUNTY PA. DESPITE ENHANCED RADAR REFLECTIVITIES ALONG THE NRN EDGE OF THE 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...WITH FREEZING LEVELS RIGHT AROUND 7KFT. LATEST WATER VAPOR IMAGERY SHOWS ANOTHER SW TROF SWINGING SOUTH THROUGH OHIO WITH AN ATTENDANT VORT MAX THROUGH SRN OHIO. THIS GENERATED LAKE ENHANCED RAIN SHOWERS OVER THE SRN SHORE OF LAKE ERIE THAT HAVE SINCE DE-TATCHED FROM THE LAKE AND HAVE CONGEALED WITH THE BACK EDGE OF THE AFOREMENTIONED CIRCULATION. THIS VORT WILL EFFECTIVELY CUT-OFF THE UPPER LOW AND ALLOW IT TO DRIFT RIGHT OVERTOP OF US. WITH COPIOUS AMOUNTS OF LLVL MOISTURE AND THE COLD POOL ALOFT...FURTHER DEVELOPMENT OF CONVECTIVELY DRIVEN RAIN SHOWERS ARE EXPECTED EAST OF LAKE-ENHANCED AXIS OF RAIN SHOWERS. 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
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... NORTHWESTERLY AND NORTHERLY FLOW IN THE LOW AND MID LEVELS CONTINUE THROUGH WEDNESDAY NIGHT AND INTO THURSDAY AS LOW LEVEL SHEAR SLOWLY INCREASES. THIS SHOULD ALLOW FOR UNSTABLE UPSLOPE FLOW SHOWERS TO SLOWLY WIND DOWN DURING THE PERIOD. SOME CLEARING SHOULD START TO WORK ITS WAY FROM WEST TO EAST ACROSS THE AREA AS LAYER MOISTURE SLOWLY PEELS OFF TO THE EAST AS WELL. YESTERDAY`S GFS...AND NOW TODAY`S ECMWF AND GFS BOTH INDICATE A SOMEWHAT ANOMALOUS LOOKING SHORT WAVE TRACKING SOUTHEASTWARD DOWN THE FRONT FLANK OF THE UPPER RIDGE THAT BUILDS TOWARD THE AREA BY LATE IN THE WEEK. DEEP MOISTURE DOES NO SEEM PARTICULARLY EVIDENT WITH THIS SYSTEM...AND THE DEPTH OF THE SYSTEM IS NOT PARTICULARLY WELL AGREED UPON. GIVEN THE FACT THAT THE GFS HAS BEEN A BIT MORE CONSISTENT WITH THE FEATURE IN ITS RUNS...TIMING AND PLACEMENT CLOSER TO THE GFS WAS FAVORED...WHICH WILL LIKELY ALLOW FOR AN INCREASE IN CLOUDS LATE IN THE WEEK...AND A VERY VERY SLIGHT CHANCE OF A FLEETING SPRINKLE. OTHERWISE...TEMPERATURES CONTINUE THEIR SLOW TREND TO CREEP BACK TOWARD NORMAL. FRIES && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... 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 /00Z WEDNESDAY THROUGH SUNDAY/... 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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