Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 062012 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 412 PM EDT MON JUL 6 2015 .SYNOPSIS... A WEAKENING WAVE OF LOW PRESSURE WILL MOVE INTO THE REGION TODAY AND TONIGHT. A COLD FRONT WILL APPROACH TUESDAY NIGHT...AND STALL ALONG JUST SOUTH OF THE MASON DIXON LINE FOR MIDWEEK. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... REGIONAL RADAR SHOWS SCATTERED SHOWERS/THUNDERSTORMS BREAKING OUT IN THE UNSTABLE AIRMASS...MAINLY OVER THE WESTERN HALF OF MY CWA AT THE CURRENT TIME. ACTIVITY BREAKING OUT OVER MD/VA STILL HAS ME CONFIDENT THAT EVEN MY EASTERN ZONES WILL SEE RAIN CHANCES INCREASE AS WE GET DEEPER INTO THE AFTERNOON. SOUTHERLY FLOW AHEAD OF A SHEARING OUT UPPER LOW/TROUGH HAS HELPED PUSH PWATS IN EXCESS OF 1.5 INCHES...SOME 1-3 STD DEV ABOVE NORMAL. RAP SHOWS MIXED LAYER CAPES IN THE 500-1000J RANGE. MID LEVEL LAPSE RATES ARE NOT TERRIBLY IMPRESSIVE SO THE CHANCES FOR SEVERE SEEM FAIRLY LOW. SPC HAS OUTLOOKED MY FAR SERN ZONES FOR A MARGINAL RISK OF SEVERE. SHEAR IS SLIGHTLY MORE IMPRESSIVE THERE...BUT AS OF MID DAY THE CONVECTION IS STILL RATHER SQUAT AND NOT ORGANIZED. MODEL BLENDED QPF OF A .25" TO .50" SEEMS REASONABLE FOR BASIN AVERAGE AMOUNTS. HOWEVER CONVECTION-ALLOWING MODELS IMPLY LOCALIZED HEAVIER AMOUNTS IN PLACES WHERE SOME TRAINING OCCURS. GIVEN THE WET GROUND AND 1HR FFG VALUES LESS THAN AN INCH OVER MUCH OF CENTRAL PA...WILL MAINTAIN THE MENTION OF LOCALIZED FLOODING IN THE HWO. BEST CHANCE SHOULD BE ACROSS THE WESTERN AND SOUTHERN COUNTIES...WHERE MOISTURE AND INSTABILITY ARE GREATEST. SHORT RANGE GUIDANCE IS CONSISTENT MAKING THE SHOWERS AND STORMS DWINDLE THIS EVENING...WITH POPS DROPPING OFF QUICKLY AFTER WE LOSE THE HEATING. THE UPPER LOW/TROUGH WILL BE FALLING APART PRETTY MUCH OVERHEAD SO OTHER THAN THE SHOWER CHANCES DROPPING OFF...TEMPS WILL NOT CHANGE MUCH LEAVING THE REGION MUGGY WITH LOWS RUNNING SEVERAL DEG ABOVE NORMAL. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... TUESDAY WILL BE VERY WARM AND MUGGY BUT MAINLY RAIN-FREE. WARMING TEMPS IN THE MID LEVELS TUESDAY AFTERNOON AND EVENING WILL HELP LIMIT/CAP OFF SHOWERS AND STORMS ACROSS MUCH OF CENTRAL PA AND THE SUSQ VALLEY. THE BEST CHANCE FOR A POP UP SHOWER OR THUNDERSTORM WILL BE IN THE AFTERNOON OR EVENING...MAINLY OVER WESTERN HIGHER ELEVATIONS. FAR NWRN PA IS OUTLOOKED FOR A MARGINAL RISK FOR LATE TUESDAY INTO THE OVERNIGHT IN ADVANCE OF A COLD FRONT APPROACHING FROM THE OHIO VALLEY. HIGH TUESDAY WILL LIKELY BE THE WARMEST THIS WEEK...AND ABOUT 3-4 DEG ABOVE NORMAL. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... THE 07/00Z MODEL AND ENSEMBLE GUIDANCE IS PROVIDING A FAIRLY CONSISTENT SIGNAL THAT THE AREA WILL REMAIN IN A LOW AMPLITUDE QUASI-ZONAL MID/UPPER FLOW PATTERN WITHIN THE NORTHERN STREAM WESTERLIES. AS MIGHT BE EXPECTED IN THIS PATTERN...THERE IS LOW PREDICTABILITY/CONFIDENCE GIVEN DEGREE OF SPREAD AND MEANINGFUL DIFFERENCES ASSOCIATED WITH SHORTWAVE DETAILS. THIS LARGELY UNSETTLED AND RECENTLY PERSISTENT WEATHER PATTERN FOR THE LOCAL AREA WILL BE MODULATED TO SOME EXTENT BY RETROGRESSION OF UNSEASONABLY STRONG UPPER TROUGH/RIDGE COUPLET OFF THE WEST COAST AND OVER THE SOUTHEAST AND SCENTRL U.S. THERE IS BROAD SUPPORT FOR ANOTHER MEAN TROUGH TO DEVELOP OVER THE NORTHEAST/MID ATLANTIC STATES BY NEXT WEEK/JULY 13TH AS ENERGY EJECTING FROM CA UPPER LOW EVOLVES DOWNSTREAM IN THE WESTERLIES AND TEAMS WITH VORTEX OVER HUDSON BAY. IN TERMS OF SENSIBLE WEATHER...A WELL-DEFINED COLD FRONT ENTERS CENTRAL PA EARLY WEDNESDAY ACCOMPANIED BY SHOWERS/TSTMS...THEN BECOMES WAVY AS IT STALLS OUT FROM NEAR THE OH RIVER/MASON DIXON LINE. EXPECT ONE OR MORE EPISODES OF PCPN THRU LATE WEEK MOST LKLY DUE TO MCS REMNANTS OR CONVECTIVELY INDUCED LOWS TRACKING EWD FROM THE MID MS/OH VLY...BUT TOO DIFFICULT TO PIN POINT TIMING/LOCATION AT THIS POINT. FWIW THE MODEL BIAS IS USUALLY TOO FAR NORTH WITH MCS ACTIVITY. PCPN RISK SHOULD EVENTUALLY BE ENHANCED TOWARD THE END OF THE PERIOD INTO EARLY NEXT WEEK AS CA LOW ENERGY AND ASSOCIATED SFC SYSTEM REACHES THE GREAT LAKES. WHAT WE CAN SAY WITH RELATIVE CERTAINTY IS THAT WE DO NOT EXPECT ANY HEAT WAVES OR EXTENDED PERIODS OF DRY WEATHER OVER THE NEXT 7+ DAYS. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... CONDITIONS OVER THE STILL MAINLY RAIN FREE LOWER SUSQ VALLEY...WITH REDUCED CONDITIONS CONTINUING OVER THE LAUREL HIGHLANDS WHERE SHOWERS ARE MORE NUMEROUS. EXPECT SHOWER ACTIVITY TO INCREASE IN COVERAGE AND SPREAD FROM SOUTH TO NORTH THROUGH THE AFTERNOON. SHOWERS WILL TEND TO BE SLOW-MOVING AND COULD PRODUCE HEAVY DOWNPOURS AND LOCAL IFR CONDITIONS. THE UPPER LOW WILL WEAKEN AS IT ENTERS CENTRAL PA OVERNIGHT...BUT WE SHOULD MAINTAIN A RISK FOR SCT SHOWERS. EXPECT CIGS/VSBYS TO TREND GRADUALLY LOWER OVERNIGHT GIVEN DIURNAL COOLING...VERY HUMID AIRMASS AND LIGHT WINDS...WITH AT LEAST MARGINAL RESTRICTIONS LIKELY AT MANY SITES INTO TUESDAY MORNING. LOWER CONDITIONS TUESDAY MORNING WILL IMPROVE BY MID MORNING TO MID DAY. A COLD FRONT WILL APPROACH THE AIRSPACE FROM THE LOWER LAKES/OH VALLEY BY LATE IN THE DAY AND SHIFT SLOWLY SEWD INTO THE AIRSPACE TUE NIGHT/WED BEFORE STALLING OUT NEAR PA/MD BORDER THURS INTO FRIDAY. OUTLOOK... TUE-FRI...VFR/MVFR WITH PERIODS OF SHRA/AFTN TSTMS. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LA CORTE NEAR TERM...LA CORTE SHORT TERM...LA CORTE LONG TERM...GARTNER/STEINBUGL AVIATION...LA CORTE

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