Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 291207 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 807 AM EDT TUE JUL 29 2014 .SYNOPSIS... AN UNSEASONABLY DEEP UPPER LEVEL LOW PRESSURE AREA OVER JAMES BAY WILL DIRECT COOL AIR INTO THE EASTERN UNITED STATES THIS WEEK. IT WILL REMAIN COOLER THAN NORMAL FOR MOST OF THE WEEK...WITH ONLY A SLIGHT WARM UP TO NEAR NORMAL TOWARD THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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12Z UPDATE...MINOR CHANGES TO GRIDDED SKY COVER BASED ON LATEST STLT IMAGERY. COULD SEE AN INCREASE IN CLOUD COVER FOR THIS AFTN WITH CU FIELD LKLY TO DEVELOP UNDER UNSEASONABLY COLD AIR ALOFT. A RATHER COOL START TO THE DAY WITH SEVERAL SITES NEAR /WITHIN 3 DEGREES OR SO/ OF DAILY RECORD LOWS FOR LATE JULY...ESPECIALLY ACRS WRN PA. OUTSIDE AN ISOLD-SCT INSTABILITY SHOWER OVER THE N/W MTNS...EXPECT A MAINLY DRY/P-M CLOUDY AND RELATIVELY COOL/COMFORTABLE FALL-LIKE DAY WITH HIGHS IN THE UPPER 60S TO MID 70S...OR ABOUT 10-15 BELOW DAILY CLIMATE NORMALS. THE BEST CHC FOR PCPN IS OVER THE WRN ZONES IN ADVANCE OF WK S/W TROUGH EMBEDDED IN BROAD CYC FLOW ALOFT...AND NEAR EDGE OF BETTER MID-LVL LAPSE RATES 6C/KM. PREVIOUS DISCUSSION... 555 DAM UPPER LOW CIRCULATING OVER JAMES BAY IS PULLING COLD AIR ACROSS THE LAKES. THE MOISTURE IS CLIMBING THE SLOPE INTO THE NORTHWESTERN AND CENTRAL MOUNTAINS. THIS SOUNDS LIKE WHAT WE WOULD NORMALLY TYPE IN MID-WINTER AND NOT IN THE DOG DAYS. THE RESULTING SENSIBLE WEATHER WILL BE A PLEASANT IF NOT CHILLY SUMMER/S DAY. HIGH TEMPERATURES WILL RUN ABOUT 5 TO 15 DEGREES BELOW NORMAL TODAY WITH 8H TEMPS ONLY IN THE MID TO UPPER SINGLE DIGITS. THE COLD AIR ALOFT WILL ALSO RESULT IN INSTABILITY SHOWERS DEVELOPING IN THE DAYTIME...MAINLY THE PEAK HEATING TIME. THE HIGHEST POPS IT IS WORTH IS ABOUT 30 DUE TO THE EXPECTEDLY SPARSE COVERAGE OVER THE NORTHWEST UNDER THE COLDEST AIR. WILL JUST MENTION A SLIGHT CHC OF T IN THE FAR NW AS WELL. THE REST OF THE AREA WILL STAY DRY WITH DEWPOINTS INCHING DOWN INTO THE M/U40S EVERYWHERE.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... SOME MEASURE OF STABILIZATION SHOULD OCCUR IN THE EVENING AND RESULT IN A QUIET NIGHT. THERE COULD STILL BE A STRAY SHOWER IN THE PRE-MIDNIGHT HOURS. BUT A LULL IN THE UPPER FORCING SHOULD DIMINISH ALL THE SHOWERS AND MANY OF THE CLOUDS OVERNIGHT. TEMPS WILL BE CHILLY AGAIN WITH LOWS TONIGHT VERY SIMILAR TO CURRENT READINGS. AROUND SUNRISE ON WEDNESDAY MOST OF THE SHORT-TERM GUIDANCE BRINGS THE NEXT WAVE OF FORCING ALONG IN THE UPPER FLOW FROM THE WEST. WINDS IN THE LOW LEVELS DO BACK A LITTLE. HEIGHTS DO NOT REALLY FALL ON WEDNESDAY...BUT THE VORT MAX IS VERY POTENT. THE BEST OF THE FORCING STAYS TO THE NORTH OF THE LOWER LAKES. WILL INTRODUCE A MENTION OF SMALL HAIL TO THE SCT/NMRS TSRA FOR THE NW ON WED AS SPC HAS ALSO MENTIONED IN THE DY2 OUTLOOK. TEMPS WILL STAY BELOW NORMAL BUT WE SHOULD ADD 3-4F ONTO WHAT WE SEE TODAY/TUES. AGAIN...WITH THE LOSS OF DAYTIME HEATING...THE SHOWERS/STORMS WILL DIMINISH AND PERHAPS QUICKLY/COMPLETELY BY 9 PM...AS THE FORCING WILL MOVE TO THE EAST AND THE FOLLOWING SUPPRESSIVE FORCING/SINKING WILL QUELL THE INSTABILITY. MEANWHILE...THE 8H TEMPS WILL HAVE WARMED A LITTLE AND WILL BE UP TO A BALMY 10C FOR THE NIGHT. DEWPOINTS WILL HAVE RISEN SLIGHTLY AND THURS MORNING LOWS WILL BE IN THE 50S AREAWIDE. && .LONG TERM /THURSDAY THROUGH MONDAY/... THE DEEP TROUGH WILL LINGER THROUGH THE WEEK WITH INDIVIDUAL IMPULSES MOVING THROUGH THE GREAT LAKES. DAYTIME HEATING AND INSTABILITY WILL BE THE FAVORED TIMES FOR SHOWERS THROUGH THURSDAY. THEN THE MODELS SHOW GOOD AGREEMENT IN RETROGRADING THE UPPER TROUGH...IN THE FRIDAY THROUGH SUNDAY TIMEFRAME. THIS ALLOWS FOR A SLIGHT REBOUND IN THE WESTERN ATLANTIC RIDGE AND FOR AN INCREASE IN MOISTURE MOVING UP THE EASTERN SEABOARD. IT WILL ALSO ALLOW FOR A MODERATION IN TEMPERATURES WITH HUMIDITY RETURNING TO SOMETHING MORE RECOGNIZABLE FOR THE HEIGHT OF SUMMER. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... STILL A LARGE AREA OF CLOUDS OVER THE AREA. NW FLOW ACROSS THE GREAT LAKES ADDING TO THE MOISTURE AND CLDS. MAIN CHANGE FOR THE 12Z TAFS IS TO SLOW DOWN CIGS GOING TO VFR. THERE COULD BE SOME SHOWERS AGAIN TODAY...BUT EXPECT LESS ACTIVITY THAN YESTERDAY. COLD AIR ALOFT WILL PRODUCE PLENTY OF AFTN CU THE NEXT SEVERAL DAYS. ON WED...NOT...THU...WE COULD SEE A LITTLE MORE IN THE WAY OF SHOWERS AND STORMS. SOME IMPROVEMENT BY THU AFT. OUTLOOK... WED...SCT PM TSRA IMPACTS POSSIBLE. THU...AM FOG POSSIBLE NW MTNS. FRI-SAT...SCT PM TSRA IMPACTS POSSIBLE. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DANGELO NEAR TERM...DANGELO/STEINBUGL SHORT TERM...DANGELO LONG TERM...LA CORTE/STEINBUGL AVIATION...MARTIN

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