Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 300730 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 330 AM EDT TUE SEP 30 2014 .SYNOPSIS... A COLD FRONT WILL DROP ACROSS THE REGION THIS AFTERNOON AND EVENING...BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS. WHILE SOME HAIL IS LIKELY TO ACCOMPANY THUNDERSTORMS OVER WESTERN AND CENTRAL SECTIONS DUE TO COLD AIR ALOFT...STRONG WIND GUSTS ARE NOT EXPECTED DUE TO RELATIVELY WEAK WINDS ALOFT. UNSETTLED WEATHER WILL MOVE EAST OF THE REGION LATER WEDNESDAY...WITH DRY WEATHER EXPECTED THROUGH THE END OF THE WEEK. A STRONGER COLD FRONT WILL PUSH EAST INTO THE COMMONWEALTH LATE FRIDAY NIGHT AND SATURDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... SHORTWAVE TROF OVER NORTHERN VIRGINIA TRACKING EASTWARD EARLY THIS MORNING...TAKING DEEPER LAYER MOISTURE AND AND SHOWER CHANCES WITH IT FOR NOW. THROUGH EARLY MORNING...MAIN SENSIBLE WEATHER CONCERN WILL BE AREAS OF FOG...WHICH WILL BE DENSE FROM THE NORTHWEST MOUNTAINS EASTWARD ACROSS THE NORTH CENTRAL MOUNTAINS AND SOUTHWARD THROUGH THE LOWER SUSQ RIVER VALLEY...ALREADY LOTS OF 1/2SM TO 1/4SM VSBYS SHOWING UP SO WILL GO AHEAD AND ISSUE DENSE FOG HEADLINES FOR THESE AREAS THROUGH 13Z. ACROSS THE LAUREL HIGHLANDS AND EXTENDING INTO THE WEST CENTRAL AND MOUNTAINS AND CENTRAL/SOUTH CENTRAL MOUNTAINS...ENOUGH OF A SOUTHERLY COMPONENT AHEAD OF THE FRONT APPROACHING THE EASTERN GLAKS TO PREVENT ANY FOG WHICH FORMS FROM BECOMING DENSE...BUT WILL CONTINUE TO MONITOR THERE. AFTER MORNING FOG DISSIPATES...AN INTERESTING CONVECTIVE DAY IS IN STORE. COLD FRONT NOW REACHING THE NORTHERN/WESTERN SHORES OF LAKE ERIE WILL SLOWLY PUSH EAST OF LAKE ERIE BY EARLY AFTERNOON. PARAMETERS SETTING UP WELL FOR HAIL TO ACCOMPANY ANY STORMS DURING MAX HEATING WITH HEALTHY CAPES (MUCAPES IN EXCESS OF 1200 J/KG) AND WET BULB ZERO BETWEEN 7K FT AND 8.5 FT ACROSS WESTERN AND CENTRAL PA. BOUNDARY LAYER WINDS ARE WEAK...SO THE MAIN THREAT WILL BE HAIL. THIS IS OUTLINED IN SPC SEE TEXT AREA OVER NORTHWEST PA. ADDED SMALL HAIL WX TYPE AS WELL...SOMETHING I USUALLY DON`T DO ON THE MID SHIFT PRECEDING A CONVECTIVE DAY...BUT GIVEN THERMO PARAMETERS HAVE HIGH CONFIDENCE IN AT LEAST SMALL HAIL TODAY WEST AND CENTRAL. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... 4KM SPC WRF INDICATES AFTERNOON CONVECTION WILL LINGER WELL INTO THE EVENING HOURS OVER ESPECIALLY CENTRAL AND EASTERN SECTIONS. AFTER STORMS DIMINISH EARLY THIS EVENING...KEPT SCATTERED SHOWERS IN THESE AREAS THROUGH LATE EVENING. FOG MAY ONCE AGAIN BECOME AN ISSUE LATE TONIGHT...ESPECIALLY OVER THE EAST WHERE SFC RIDGE AXIS BUILDS AND A WEAK INVERSION SETS UP IN LIGHTS WINDS. MINS WILL RANGE THROUGH THE 50S. SLOWLY FILLING UPPER TROF WOBBLES SLOWLY EASTWARD ACROSS THE COMMONWEALTH ON WEDNESDAY. IT LOOKS QUITE CLOUDY GIVEN FAIRLY STEEP LAPSE RATES...BUT GENERALLY DRY WITH ONLY SLGT CHC POPS UNDER THE "COOL" CORE ALOFT. AN UNDERWHELMING UPPER LOW OF 571 DM TRACKS INTO SOUTHERN NEW ENGLAND BY 00Z THU...WITH RISING HEIGHTS LATE IN THE DAY ACROSS WESTERN AND CENTRAL PA. TEMPS ON WED HOWEVER WILL BE COOLER THAN RECENT DAYS...DUE TO THE CLOUD COVER. EXPECT HIGHS TO RANGE FROM THE UPPER 60S NORTH TO THE LOWER 70S SOUTH. && .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. 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 /07Z TUESDAY THROUGH SATURDAY/... 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...DEVOIR NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...LAMBERT/GARTNER AVIATION...STEINBUGL

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