Area Forecast Discussion
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000 FXUS61 KPBZ 181814 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 214 PM EDT SAT OCT 18 2014 .SYNOPSIS... SHOWERS AND MUCH COLDER TEMPERATURES ARE EXPECTED TODAY. SHOWERS WILL END LATE TONIGHT...BUT TEMPERATURES ON SUNDAY WILL REMAIN BELOW NORMAL. && .NEAR TERM /THROUGH SUNDAY NIGHT/... CDFNT HAS CROSSED THE FCST AREA...WITH TEMPS GENLY XPCD TO INCR VERY LITTLE RMNDR OF TDA OWING TO STRONG COLD AIR ADVCTN OFFSET ONLY BY A FEW BREAKS IN CLD CVR. GUSTY NWLY WINDS XPCD TO CONT THRU THIS EVE AS STEEPENING LOW-LVL LAPSE RATES PROMOTE MIXING. SHRTWV TROF WILL SUPPORT SCT-NMRS SHWRS THIS AFTN AND EVE...SPCLY NRN HALF OF FCST AREA. PROLONGED NWLY FLOW WILL INCR UPSLOPE COMPONENT OF WIND ON RDGS...WHERE POPS WERE INCRD TO CATEGORICAL LATE THIS AFTN AND EVE. ALTHOUGH RAIN AMTS WILL NOT BE HIGH...PCPN XPCD TO BE MEASURABLE. CLD CVR WILL PERSIST MUCH OF TNGT BUT MAY BGN TO CLR EARLY SUN MRNG IN ERN OH ZONES. GIVEN LATE DEPARTURE OF ANY CLDS...FROST DVLPMT APPEARS UNLKLY ATTM. PATCHY FROST MAY BE INCLD WITH LATER FCST. OTHERWISE...MINIMA XPCD TO RMN IN MID-UPR 30S MOST AREAS. PCPN IN RDG ZONES WILL CONT INTO THIS EVE BUT WILL BGN TO WANE AS UPR SUPPORT PROGRESSES EWD. PREV SHIFT HAD CONFIDENCE THAT PCPN WOULD END BY 06Z...BUT LATEST GUIDANCE SUGGESTS VERY LGT PCPN MAY CONT THRU LATE TNGT. AFTER 06Z...THERE MAY BE A FEW SNOWFLAKES MIXED IN WITH ANY LINGERING RAIN...BUT NO SGFNT ACCUMS XPCD. SFC HIPRES WILL TRANSITION EWD ON SUN...WITH FLOW BCMG LGT TO SLY. THIS SLY FLOW WILL PROMOTE MODEST INCR IN TEMPS FOR WRN ZONES BY SUN AFTN...ALTHOUGH SUN GENLY WILL NOT BE MUCH WARMER THAN TDA GIVEN CLD CVR LINGERING INTO MID-DAY. ONCE LOW CLDS VACATE...HIGH CLDS XPCD TO INCR IN CVRG AS A JET MAX DVLPS IN ASSOCIATION WITH SHRTWV TROF APRCHG FROM NW. SFC HIPRES WILL ATTEMPT TO ASSERT ITSELF SUN EVE BUT WILL BE SUPPLANTED SWD LATE SUN NGT AS H5 TROF DIGS INTO GRTLKS RGN. SLY WIND AND INCRD CLD CVR FROM MID-LVL JET WILL RETARD COOLING SUN NGT AND WILL PREVENT FROST FROM BEING A CONCERN. PCPN CHCS WILL INCR LATE SUN NGT AS MID-LVL SATURATED LYR DPNS AND LWRS. POPS WERE LWRD SUN EVE...BUT WERE INCRD AFTER 20/06Z AS LGT PCPN XPCD TO DVLP AND SPREAD SEWD INTO FAR WRN ZONES. && .SHORT TERM /MONDAY THROUGH TUESDAY/... WARM ADVECTION BEGINS TO AFFECT THE AREA ON MONDAY WITH SOUTHWESTERLY FLOW CONTINUING INTO MONDAY NIGHT. THIS COMBINED WITH 850 MB TEMPERATURES RISING UP TOWARD +4C SHOULD ALLOW FOR A POOR DIURNAL TEMPERATURE FALL ON MONDAY NIGHT IN ADVANCE OF THE NEXT SERIES OF WAVES WHICH WILL BEGIN TO CROSS THE AREA ON MONDAY. THE FIRST WAVE LOOKS RATHER HIGHLY SHEARED AND MOISTURE STARVED ON MONDAY...WITH A LAYER OF DRY AIR BELOW IT LIKELY TO ERODE WHAT LITTLE BIT OF PRECIPITATION MAY BE GENERATED FROM THE WEAK ELEVATED SATURATION AND LIFT IT MANAGES TO MUSTER. A DEEPER WAVE WILL MOVE AROUND THE BASE OF THE TROUGH FOR MONDAY NIGHT...DECREASING ITS TILT AS IT DOES SO. THIS WILL AGAIN WORK A BIT WARMER LOW LEVEL AIR TOWARD THE AREA FOR MONDAY NIGHT...WHILE YIELDING A WINDOW OF REDUCED CHANCES OF RAINFALL IMMEDIATELY PRECEDING IT. HOWEVER...BY MONDAY LATE AFTERNOON AND EVENING...RAIN SHOULD AGAIN OVERSPREAD THE AREA SLOWLY FROM NORTHWEST TO SOUTHEAST AND CONTINUE INTO TUESDAY. YET ANOTHER DEEPER WAVE WILL TRAVERSE THE LONG WAVE TROUGH GOING INTO TUESDAY...WHICH WILL AGAIN INCREASE THE CHANCE OF PRECIPITATION OWING TO PROGRESSIVELY COLDER AIR ALOFT. IT IS THIS WAVE THAT SEEMS TO BE THE CULPRIT IN REALLY HALTING THE EASTWARD PROGRESSION OF THE LONG WAVE PATTERN. AS IT DIVES INTO THE BASE OF THE LONG WAVE TROUGH ON TUESDAY...MODEL SOLUTIONS BEGIN TO FAVOR A CLOSING OFF OF THE MID AND UPPER LEVELS...IN ADVANCE OF THE EVENTUAL CUTTING OFF OF THE MID/UPPER LEVEL FLOW OVER OUR AREA FROM THE POLAR JET. FRIES && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... MODELS CONTINUE TO FLIP FLOP ON HOW FAR EAST THE CLOSED/CUT OFF LOW WILL END UP AFTER MID-WEEK. CURRENT SOLUTIONS ARE AGAIN TOO CLOSE TO THE FORECAST AREA TO KEEP THE MENTION OF RAIN CHANCES OUT OF THE FORECAST UNTIL AFTER WEDNESDAY NIGHT. HOWEVER...EVEN STILL...CLOUDS ARE STILL LIKELY TO REMAIN A PLAYER THROUGH MUCH OF THE COMING WEEK. FRIES && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... SCT-NMRS RAIN SHWRS WILL BE SUSTAINED THIS AFTN NR AND N OF KPIT AS SHRTWV TROF CROSSES GRTLKS RGN. NWLY SFC WIND WILL GUST 20-25KT BFR SUBSIDING THIS EVE. MVFR CIGS XPCD RMNDR OF TDA...WITH VSBY AND CIGS PSBLY LWR IN SHWRS. STRATOCU WILL PERSIST TNGT AMID COLD ADVCTN AND LWRG INVERSION HEIGHTS. CIGS LKLY WILL RMN IN MVFR CATEGORY THRU SUN MID-AFTN. .AVIATION /SUNDAY THROUGH WEDNESDAY/... PERIODIC RESTRICTIONS ARE EXPECTED TO PERSIST THROUGH EARLY NEXT WEEK AS UPR TROFG CONTS IN THE UPR OH REGION. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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