Area Forecast Discussion
Issued by NWS State College, PA

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279 FXUS61 KCTP 190647 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 247 AM EDT TUE MAY 19 2015 .SYNOPSIS...
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A COLD FRONT WILL MOVE ACROSS CENTRAL PENNSYLVANIA TODAY WITH A MARGINAL/ISOLATED SEVERE WEATHER RISK FROM THE EASTERN COAL REGION INTO THE POCONOS. A COOLER WEATHER PATTERN WILL GRIP THE REGION INTO THE WEEKEND BEFORE SUMMER HEAT RETURNS BY MEMORIAL DAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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06Z RADAR SHOWS SCT SHOWERS MAINLY S/E OF I-99 CORRIDOR WITH THE GREATEST CONCENTRATION /INCLUDING RECENT UPTICK/ OF PCPN ACTIVITY FOCUSED OVER THE LWR SQV. HRRR FAVORS THIS SCENARIO AND PLACED HIGHEST POPS FROM THE SOUTH-CENTRAL MTNS NEWD INTO THRU THE SUSQ VLY. SUBTLE BACKDOOR TYPE FRONT HAS ALLOWED MARINE AIR/EASTERLY LLVL FLOW TO PENETRATE WWD TO ALONG THE SUSQ RIVER WITH WDSPRD LOW CIGS AND FOG EXPECTED TO PERSIST THROUGH DAYBREAK. TO THE WEST...WEAK BUT MOIST UPSLOPE IS PROMOTING LOW CIGS AND FOG ALONG THE RT 219 CORRIDOR. SITES SUCH AS AOO/UNV WILL LKLY SEE AT LEAST SOME PATCHY FOG GIVEN LGT WINDS AND MUGGY AIR W/60-65F DEWPTS BUT MAY ESCAPE THE WORST CONDITIONS. SHORTWAVE CURRENTLY MOVING THROUGH THE WESTERN GREAT LAKES WILL TEAM WITH ADDITIONAL ENERGY DROPPING DOWN FROM HUDSON BAY UPPER TROUGH TO FLATTEN THE ANOMALOUS RIDGE OVER THE NORTHEASTERN U.S. ONCE THE LOW CLOUDS/FOG ARE ERODED...STRONG PRE-FRONTAL BOUNDARY LAYER WARMING SHOULD PROVE MORE THAN ADEQUATE FOR CONVECTION WITH HRRR SHOWING DEVELOPMENT ALONG/EAST OF THE SUSQ VLY BY 18-19Z. SPC HAS OUTLOOKED EAST-CENTRAL PA FROM THE COAL REGION ENEWD INTO THE POCONOS WITH MARGINAL SEVERE RISK WITH INCREASING SHEAR TO THE NORTH. HOWEVER DESPITE WEAKER FLOW ALOFT...CANT RULE OUT THREAT FOR GUSTY WINDS/SMALL HAIL IN MORE CAPE-DRIVEN STORMS IN STEEP LLVL LAPSE RATE ENVIRONMENT OVER THE LWR SQV. HEAVY DOWNPOURS COULD POSE MINOR FLOOD THREAT PROBABLY MORE SO TO URBAN/POOR DRAINAGE AREAS VS. SMALL STREAMS GIVEN RECENT DRY CONDITIONS AND BELOW NORMAL STREAM FLOWS FOR THIS TIME OF YEAR. ANY EARLY EVENING ACTIVITY OVER FAR ERN SXNS SHOULD PUSH OUT OF THE CWA AFTER 00Z AS NOTICEABLY DRIER AIR SPREADS ACROSS THE AREA IN THE WAKE OF THE COLD FRONT.
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&& .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
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A COOLER BROAD CYCLONIC FLOW WILL BEGIN TO GRIP THE REGION ON WEDNESDAY WITH DAYTIME HIGHS SOME 15-20F COOLER THAN TODAY. THE COOLER AIR ALOFT SHOULD PROMOTE AFTN CU DEVELOPMENT WITH A NW BREEZE ADDING TO THE RELATIVE CHILL. THE MODELS SHOW A SHORTWAVE TROUGH MOVING QUICKLY FROM THE UPPER GREAT LAKES TOWARD THE MID ATLANTIC WITH SOME SHOWERS POSSIBLY REACHING THE SW MTNS BY 12Z THU. THE OTHER CONCERN IS FROST FOR THE NRN MTNS WITH THE FINAL 3 ZONES STARTING THE GROWING SEASON ON 5/21 BUT THE OVERALL PATTERN DOES NOT LOOK THAT FAVORABLE ATTM SUGGESTING LOW CONFIDENCE.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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A WEAK WAVE EJECTS EASTWARD FROM THE S PLAINS TOWARD THE CAROLINA/S ON THU...WHILE TROUGH CONTINUES TO SPIN OVER EASTERN CANADA. CENTRAL PA REMAINS BETWEEN THESE TWO FEATURES...WHICH WILL KEEP US DRY. EVEN WITH NW FLOW...DAYTIME TEMPS WILL REBOUND A BIT WARMER EACH DAY. BUT DIURNAL TEMP RANGES WILL BE FAIRLY LARGE THANKS TO THE DRIER AIRMASS...WHICH WILL BRING CHILLY MORNINGS. THE COLDEST CONTINUES TO LOOK LIKE THURSDAY MORNING WHERE THERE REMAINS A RISK FOR PATCHY FROST...MAINLY OVER THE NORTH-CENTRAL ZONES WHERE GUIDANCE IS SHOWING POSS FOR MID 30S AOA BFD /JUST IN TIME FOR THE START OF THE GROWING SEASON/. THE WEAK LOW OVER CAROLINAS/MID ATLANTIC REGION SLIDES OFFSHORE FRI...WITH SPRAWLING HIGH PRESSURE AREA BUILDING IN FOR SAT/SUN. ONCE RIDGE AXIS SLIDES BY SAT NIGHT...HUMIDITY WILL BEGIN TO SLOWLY INCREASE ON SUNDAY WITH RISING TEMPS /AND ISOLATED LATE DAY CONVECTION POSS/. WARMER AND MUGGIER CONDITIONS ON MEMORIAL DAY...WITH SCATTERED TO EVEN NUMEROUS SHOWERS/TSTMS IN THE FORECAST.
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&& .AVIATION /06Z TUESDAY THROUGH SATURDAY/... AN UNSTABLE AIR MASS AHEAD OF AN APPROACHING COLD FRONT WILL ALLOW FOR SCATTERED SHRA TO CONTINUE TO MOVE ACROSS CENTRAL PA OVERNIGHT. ANY OF THESE SHRA COULD PRODUCE BRIEF VIS REDUCTIONS. HOWEVER...THE MAIN AVIATION CONCERN OVERNIGHT AND THROUGH THE FIRST HALF OF THE MORNING WILL BE THE DEVELOPING LOW CIGS ACROSS CENTRAL PA. THE LOW CIGS IN EASTERN PA IS A RESULT OF MARINE AIR FLOWING OFF THE ATLANTIC OCEAN...COUPLED WITH THE AMPLE LOW LEVEL MOISTURE PROVIDED BY THE SHOWERS FROM EARLIER. IFR CIGS ARE ALREADY PRESENT ACROSS MUCH OF EASTERN AND WESTERN PA AT 06Z...WITH AOO AND UNV THE LONE HOLD OUTS. NEAR TERM MDL DATA SUPPORT THESE LOW CIGS CONTINUING THROUGH 12Z. THE WESTERN TAF SITES THAT ARE IFR ARE DUE TO A PLUME OF MOISTURE AHEAD OF APPROACHING COLD FRONT THAT WILL ASCEND THE W MTNS...LIKELY RESULTING IN IFR CIGS AT KBFD/KJST OVERNIGHT. BOTH THE SREF AND LATEST HRRR SUPPORT THIS SCENARIO. MOST FAVORABLE CONDS OVERNIGHT SHOULD BE AT KAOO/KUNV...WHERE SIG REDUCTIONS APPEAR UNLIKELY. LOW CIGS ACROSS THE W MTNS AND EASTERN PA SHOULD LIFT BY LATE AM. CAN/T RULE OUT AN ISOLD SHRA/TSRA ACROSS EASTERN PA ARND MIDDAY WITH PASSAGE OF COLD FRONT. OTHERWISE...EXPECT A RETURN TO WIDESPREAD VFR CONDS...AS A GUSTY WEST WIND BRINGS MUCH DRIER AIR INTO THE REGION BEHIND THE COLD FRONT. OUTLOOK... WED-SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...STEINBUGL NEAR TERM...STEINBUGL SHORT TERM...STEINBUGL LONG TERM...RXR AVIATION...FITZGERALD/CERU

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