Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 210251 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1051 PM EDT MON OCT 20 2014 .SYNOPSIS... LOW PRESSURE AT THE SURFACE AND ALOFT WILL BE DRIFTING SOUTHEAST ACROSS THE LOWER GREAT LAKES TONIGHT. THIS FEATURE WILL FILL IN SLOWLY AS IT MOVES OVER THE STATE...THEN RE-FORMS JUST OFF THE COAST ON TUESDAY. THE LOW PRESSURE WILL LINGER OFF THE MID ATLANTIC COAST AND KEEP IT DAMP AND SHOWERY INTO WEDNESDAY. CONDITIONS WILL SLOWLY IMPROVE DURING THE LATTER PART OF THE WEEK...AS THE STORM SLOWLY MOVES AWAY FROM THE AREA. && .NEAR TERM /UNTIL 8 AM TUESDAY MORNING/... SFC LOW ON THE EASTERN SHORE OF GEORGIAN BAY HAS A COLD FRONT EXTENDING SSW THROUGH KCLE AND KCVG AT 02Z TUES. A COMPACT...BUT RATHER POTENT MID/UPPER LEVEL VORT MAX IS WELL-DEFINED IN BOTH WATER VAPOR IMAGERY AND REGION 88D REFL LOOP JUST SW OF KPIT. TSRA HAVE DIMINISHED IN AREAL COVERAGE AND HAVE BECOME CONFINED TO SRN OHIO ATTM...WITHIN A POCKET OF 850-500MB LAPSE RATES ON THE ORDER OF 6.5C/KM. SHOWERS ACROSS EASTERN OHIO AND NWRN PENN WILL /WITH NARROW BANDS OF SHRA ACROSS CENTRAL AND SERN PENN/ WILL CONTINUE TO DRIFT TO THE EAST OVERNIGHT. ACROSS THE LOWER SUSQ VALLEY...AN INJECTION OF LLVL MOISTURE VIA A SSE FLOW OFF THE CHESAPEAKE WILL COMBINE WITH ENHANCED LIFT BENEATH THE RIGHT ENTRANCE REGION OF A 90 SWRLY JET MAX...A WEAK SFC/LEE TROUGH...AND INCREASING LLVL CONVERGENCE AT THE NOSE OF A 35 KTS SWRLY 850 MB JET TO BRING AN AREA OF SHOWERS IN FROM MD AND NRN VA. RAINFALL OVERNIGHT WILL BE GENERALLY LIGHT AND LESS THAN ONE TENTH OF AN INCH IN MOST PLACES. THE EXCEPTION WILL BE ACROSS THE NW MTNS /AND PERHAPS THE LAURELS/ WHERE UP TO 2 OR 3 TENTHS IS POSSIBLE. WILL KEEP POPS GENERALLY LOW UNTIL AROUND OR SHORTLY AFTER MIDNIGHT OVER THE EASTERN PORTIONS OF THE FCST AREA. THE PROB OF RAIN WAS MODIFIED A BIT FOR THE OVERNIGHT...WITH 80-100 POPS ACROSS THE NWRN HALF OF THE CWA...TRENDING TO HIGH CHC/LOW LIKELY FOR THE SE HALF OF THE FCST AREA. TEMPS SHOULD STAY RATHER MILD FOR THIS TIME OF YEAR UNDER THE CLOUDS AND INITIAL/LIGHT SRLY SFC WIND. LOWS WILL BE IN THE LOWER TO MID 40S. && .SHORT TERM /8 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... THE LOWERED PRESSURES WILL SLIDE EASTWARD ON TUESDAY AND BY TUES NIGHT A DEEPER LOW WILL FORM NEAR ATLANTIC CITY. WILL NOT GAMBLE AND WILL GO WITH THE VERY HIGH PROBABILITY FORECAST WHICH BY NO CHANCE IS ALSO CONTINUITY. COOL BUT WET NRLY/WRLY FLOW AROUND THE LOW WILL CREATE VERY CLOUDY AND DAMP WX OVER THE SHORT RANGE PERIOD. THE UPPER LOW WILL BE OVERHEAD TUESDAY NIGHT AND THE FALLING HEIGHTS AND COOLER AIR ALOFT /WITH 850-500 MB LAPSE RATES OF 6-6.5C/KM/ DURING THE DAY TUESDAY COULD ALLOW FOR SEVERAL HUNDRED J/KG OF CAPE TO DEVELOP ACROSS PRIMARILY THE SUSQ VALLEY/. CONDITIONS THERE WILL BE VERY SIMILAR TO WHAT WE/RE CURRENTLY SEEING IN SUPPORT OF THE TSRA ACROSS CENTRAL OHIO. DIURNAL TEMP RANGE TUES WILL BE JUST 8-12F IN MOST PLACES...WHICH WILL HELP TO KEEP MAXES BELOW NORMALS. 8H TEMPS GENERALLY STAY ABOVE ZERO. BUT LATE TUES NIGHT/WED AM MAY BE COLD ENOUGH OVER THE LAURELS TO HAVE SOME SNOW MIX IN WITH ANY RAIN SHOWERS ON THE HIGHEST ELEVS. HAVE CHOSEN TO LEAVE OUT MENTIONS OF ANY MIX AT THIS POINT. THE CORE OF THE COLD AIR COULD GO TO OUR SOUTH WITH HELP FROM THE CIRCULATION OF THE UPPER LOW...WHICH KEEPS THAT MARITIME AIR WRAPPING IN TO THE AREA. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... AN UNUSUALLY HIGH DEGREE OF MODEL/ENSEMBLE AGREEMENT IS LEADING TO A HIGH CONFIDENCE FORECAST FOR MUCH OF THE LONG TERM PERIOD. THE OVERWHELMINGLY DOMINANT MAIN FEATURE TO AFFECT THE LOCAL AREA DURING THIS PERIOD WILL BE A CUT-OFF...SLOW-MOVING UPPER LOW...PROGGED TO GRADUALLY DEEPEN AS IT DRIFTS OVERHEAD AND REACHES THE EAST COAST /TO AROUND 550DM/ THEN PICK UP SOME SPEED AS IT LIFTS TO THE NORTHEAST THROUGH THE FIRST HALF OF THE LONG TERM PERIOD. THE POSITION OF THE STORM WILL KEEP LOTS OF MARITIME AIR FLOWING IN FROM THE NORTH/EAST AND KEEP POPS PRETTY HIGH ON WED...BUT SOME IMPROVEMENT IS POSSIBLE ON THURSDAY. THE HIGHEST POPS WILL GENERALLY BE IN THE NRN HALF - ESP THE NE. BUT THE MOISTURE WILL WRAP AROUND THE STORM COMPLETELY AT TIMES. THUS...A MOIST UPSLOPE FLOW IN THE WRN MTNS WILL KEEP PLENTY OF CLOUDS IN PLACE WITH SHOWER CHCS HIGH THERE AS WELL DURING MID-WEEK. AS A SURFACE LOW DEVELOPS UNDER THE UPPER SYSTEM OFF THE NJ/NY COAST...NORTHERLY LOW LEVEL FLOW WILL INCREASE AND BRING A PERIOD OF BREEZY CONDITIONS WED INTO THU...AND POSS EVEN INTO FRI. EVENTUALLY...SFC HIGH PRESSURE AND CONCURRENT UPPER RIDGING SHOULD LEAD TO A DRY WEEKEND WITH WESTERLY FLOW AND MILDER TEMPERATURES ON SAT. THERE COULD BE A WEAK AND DRY FRONT DROP ACROSS THE GREAT LAKES AND MID-ATLANTIC ON SUNDAY...WHICH MAY PRODUCE WIDELY SCT SHOWERS...BUT IT IS NOT WORTH A POP AT THIS POINT. TEMPS MAY THEN DIP A FEW DEGS FROM SAT-SUN. OTHERWISE... GENERALLY ZONAL FLOW LOOKS TO BE THE RULE AT THE LONGEST OF RANGES IN THE LOCAL FORECAST WITH CHANCE FOR JUST WEAK WAVES TO IMPACT CENTRAL PA. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... LOW PRESSURE APPROACHING FROM THE GRT LKS WILL BRING DETERIORATING FLYING CONDS TO CENTRAL PA TONIGHT IN THE FORM OF LOWERING CIGS AND SHOWERS. AS OF 23Z...WIDESPREAD VFR CONDS REPORTED. HOWEVER...A PERIOD OF STEADY RAIN IS LIKELY TO MOVE INTO THE NW MTNS THIS EVENING AND SCT SHOWERS ARE LIKELY ELSEWHERE OVERNIGHT. MAIN CONCERN OVERNIGHT WILL BE DEVELOPING LOW CIGS AT KBFD. MDLS SUGGEST AN INCREASINGLY MOIST SOUTHERLY FLOW ASCENDING THE NW MTNS WILL CAUSE CIGS TO FALL INTO THE IFR RANGE AT KBFD LATE TONIGHT. ELSEWHERE...NO WORSE THAN MVFR CONDS EXPECTED OVERNIGHT. AS COLD FRONT PUSHES THRU TUE AM...WIND WILL SHIFT FROM SOUTHERLY TO NWRLY. THE RESULTING UPSLOPE FLOW OVR THE LAUREL HIGHLANDS WILL PLACE KJST AT RISK FOR IFR CIGS BTWN 11Z-15Z. EXPECT RISING CIGS EVERYWHERE BY AFTN...AS MODEST DIURNAL WARMING OCCURS WITHIN THE SFC TO 1KM LAYER. BY AFTN...MDL SOUNDINGS AND MOS GUIDANCE SUPPORT MVFR CIGS AT KBFD/KJST...WITH PREDOMINATELY VFR CONDS FURTHER EAST. HOWEVER...COOL TEMPS ALOFT WILL CREATE AN UNSTABLE ENVIRONMENT THAT WILL LEAD TO NUMEROUS PM SHRA AND EVEN A POSS TSRA. ANY OF THESE SHRA/TSRA COULD PRODUCE A BRIEF DIP TO IFR VSBY. SCT SHOWERS OF DIMINISHING INTENSITY WILL CONTINUE TO AFFECT THE REGION TUE NIGHT...AS SLOW MOVING LOW PRES SYSTEM MOVES THRU THE AREA. HOWEVER...BIGGEST AVIATION CONCERN WILL BE THE POTENTIAL OF LOW CIGS REDEVELOPING TUE NIGHT AT KBFD/KJST...THE RESULT OF RADIATIONAL COOLING OF THE SFC-1KM LAYER AND UPSLOPE FLOW. DOWNSLOPING NW FLOW SHOULD YIELD MUCH MORE FAVORABLE CONDS FURTHER EAST. OUTLOOK... WED-FRI...LOW CIGS POSS W MTNS...MAINLY AT NIGHT/EARLY AM. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DANGELO/LAMBERT NEAR TERM...LAMBERT SHORT TERM...DANGELO/LAMBERT LONG TERM...RXR AVIATION...FITZGERALD

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