Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 300631 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 231 AM EDT TUE SEP 30 2014 .SYNOPSIS... A WEAK COLD FRONT AND AN UPPER LEVEL DISTURBANCE WILL MOVE OUT OF THE GREAT LAKES AND BRING AN INCREASE IN CLOUDS ALONG WITH SOME SHOWERS OR THUNDERSTORMS TUESDAY INTO WEDNESDAY. A STRONGER COLD FRONT WILL PUSH EAST INTO THE COMMONWEALTH LATE FRIDAY NIGHT OR SATURDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... A LONE SHOWER COULD AFFECT A FEW SPOTS ALONG THE MASON DIXON LINE IN YORK AND ADAMS CO BTWN 04Z-07Z. SHIELD OF MID AND HIGH LVL CLOUDS OVER EASTERN PA SHOULD PUSH EAST OF THE AREA BY ARND 06Z...AS SHORTWAVE AND ASSOC WAA ALOFT SHIFT EAST OF THE STATE. CENTRAL PA WILL BE IN BTWN SHORTWAVES TONIGHT...ONE DEPARTING THE E COAST AND NEXT SHORTWAVE DIVING ACROSS THE GRT LKS. LG SCALE SUBSIDENCE BTWN THESE SYSTEMS SHOULD ENSURE A DRY FCST OVERNIGHT. MCLEAR SKIES AND A CALM WIND WILL PROMOTE AREAS OF LATE NIGHT VALLEY FOG. LATEST SREF AND RAP OUTPUT SUGGEST...UNLIKE MANY RECENT NIGHTS...SOME OF THE FOG COULD AFFECT EVEN THE LOWER SUSQ VALLEY. DWPTS IN THE 50S SHOULD TRANSLATE TO ANOTHER MILD NIGHT FOR LATE SEPT...WITH LOWS MOSTLY IN THE L/M 50S. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... A POTENT UPPER SHORTWAVE/LOW OVR THE GRT LKS WILL DIVE SE ACROSS PA ON TUESDAY. DECREASING STABILITY UNDER THE COLD POOL ALOFT WILL HELP SUPPORT THE DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS. ENSEMBLES AND OPERATIONAL GUIDANCE INDICATE THAT CAPE WILL BE MODEST...BUT FORECAST TOTAL-TOTALS IN EXCESS OF 50 ARE USUALLY A GOOD INDICATOR FOR THE POTENTIAL OF SOME LOW TOPPED CONVECTION. BASIN AVERAGE RAINFALL IS EXPECTED TO BE LIGHT...ON THE ORDER OF 0.10 OF AN INCH OR LESS...BUT AMOUNTS COULD BE SLIGHTLY HEAVIER...0.15 TO 0.25 OF AN INCH...ACROSS THE FAR NW TUESDAY AFTERNOON AND EVENING. MAX TEMPS TUESDAY ARE EXPECTED TO BE JUST A FEW DEG COOLER AND IN THE LOWER TO MID 70S. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... PROGRESSIVE UPPER LOW/COMPACT TROF AXIS OVER THE NERN U.S. AT THE START OF THE PERIOD IS FORECAST TO LIFT OUT BY THE END OF THE WEEK...AS UPPER RIDGE REBUILDS ACROSS THE REGION INTO THE EARLY PART OF THE WEEKEND. A SECOND...MUCH STRONGER AND EXPANSIVE UPPER TROF AXIS EXTENDING SWD FROM AN UPPER LOW ANCHORED OVER NRN ONTARIO IS FORECAST TO SWEEP ACROSS THE EASTERN U.S. OVER THE WEEKEND. CLOUDIER AND MORE UNSETTLED WEATHER THAN RECENT DAYS IS EXPECTED TO ACCOMPANY THE FIRST TROF WED...HOWEVER THE SYSTEM IS SOMEWHAT MOISTURE-LIMITED AND SIGNIFICANT PCPN IS NOT EXPECTED. TEMPS ON WED HOWEVER WILL BE COOLER THAN RECENT DAYS. WARMER WEATHER MAKES A BRIEF RETURN THUR...FRI AND EARLY SAT AS THE UPPER RIDGE REBUILDS....WITH MAXES AND MINS AT LEAST SEVERAL DEGREES ABOVE CLIMO NORMALS. THE ARRIVAL OF THE SECOND TROF WILL SUPPORT A STRONG COLD FRONT WITH DEEPER CONNECTIONS TO THE GOMEX AND THE ATLANTIC OCEAN...THUS POTENTIAL FOR MORE WIDESPREAD AND HEAVIER RAINFALL. PASSAGE OF THE FRONT WILL ALSO BRING NOTICEABLY COOLER TEMPS TO THE REGION FOR SUNDAY INTO MONDAY. A SHORT WAVE WITHIN THE THEN EXPECTED CYCLONIC FLOW OVER THE REGION WILL BRING ANOTHER FRONTAL SYSTEM TO THE REGION WITH AN INCREASED CHANCE OF SHOWERS FOR THE END OF THE PERIOD. && .AVIATION /06Z TUESDAY THROUGH 06Z WEDNESDAY/... CLR SKIES/LGT WINDS AGAIN SUPPORTING VALLEY FOG FORMATION ACRS CENTRAL PA. HIGHEST CONFIDENCE IN IFR OR BLW AT BFD/IPT/LNS (PERSISTENCE) FOLLOWED BY AOO/UNV. MDT HAS YET TO REALLY GET INTO THE FOG OVER THE LAST SEVERAL DAYS AND WILL CAP VSBY AT 3-5SM. DEWPT DEPRESSION AT JST SUGGEST FOG IS UNLIKELY ALTHOUGH DID SHOW SCT015 GROUP TWD DAYBREAK. FOG WILL GIVE WAY TO VFR FOR THE MORNING HOURS...AHEAD OF COMPACT UPPER LEVEL LOW AND WEAK COLD FRONT FCST TO SHIFT SEWD FROM THE GRT LKS ACRS PA LATER TODAY INTO TNGT. MODEL GUIDANCE IS SUPPORTIVE OF VCSH/-SHRA MENTION AT ALL SITES FROM THIS AFTN INTO EARLY TNGT ALONG WITH A GENERAL LOWERING TREND IN CIGS/VSBYS. ARRIVAL OF COOLING ALOFT ASSOCD WITH UPPER LOW FAVORABLY TIMED WITH DAYTIME HEATING SHOULD SUPPORT ISOLD-SCT TSTM DEVELOPMENT...FOCUSING ALONG/AHEAD OF SFC COLD FRONT. THE COOL TEMPS ALOFT WILL FAVOR HAIL AS THE PRIMARY TSTM HAZARD. OUTLOOK /WEDNESDAY THROUGH SATURDAY/... WED...UPPER LOW WILL BE SLOW TO MOVE NEWD THEREFORE CHC OF SHOWERS WILL CONTINUE ON WED. SOME LOW CIGS PSBL AS WELL. THU...LOW CIGS LKLY EARLY...AND COULD PERSIST THRU MUCH OF THE DAY OR REFORM THU NGT DUE TO HIGH PRES WEDGE/MARITIME FLOW E OF THE APPLCHNS. FRI...SHOWERS AND THUNDERSTORMS LKLY ASSOCD WITH WELL-DEFINED GUSTY COLD FROPA. LLWS LKLY DUE TO STG SLY WINDS AHEAD OF THE COLD FRONT. SAT...AM SHOWERS ERN AREAS. BREEZY WITH IMPROVING CONDITIONS E OF THE MTNS DUE TO WLY DOWNSLOPE. ISOLD SHOWERS AND LOCAL MVFR POSSIBLE OVER N/WRN AREAS. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LA CORTE NEAR TERM...DEVOIR/FITZGERALD SHORT TERM...FITZGERALD/LA CORTE LONG TERM...LAMBERT/GARTNER AVIATION...STEINBUGL

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