Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 241827 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 227 PM EDT THU JUL 24 2014 .SYNOPSIS... HIGH PRESSURE AND A REFRESHINGLY COOLER AND LESS HUMID AIRMASS WILL PUSH SOUTHEAST FROM THE GREAT LAKES REGION TODAY AND STAY WITH US RIGHT INTO SATURDAY. A WARM FRONT WILL SLIDE EAST OUT OF THE OHIO VALLEY LATE SATURDAY FOLLOWED BY A WAVY...SLOW MOVING COLD FRONT FOR SUNDAY INTO SUNDAY NIGHT. PERIODS OF SHOWERS AND THUNDERSTORMS WILL AFFECT CENTRAL PENNSYLVANIA AND THE ALLEGHENY PLATEAU SATURDAY NIGHT THROUGH SUNDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... COLD AIR ALOFT AND GOOD SOLAR HEATING GENERATED LOTS OF CU OVER THE ENTIRE REGION. THE WEAK/MODERATE SHORT WAVE TROUGH PASSING OVERHEAD WILL BE PUSHING TO THE S/E SOON AND DIURNAL HEATING ON IT/S WAY DOWN SOON AS WELL. CLOUDS ARE ALREADY ON THE DECREASE AT 18Z AS DRY AIR HAS MIXED WELL/DEEP. BY SUNSET A LOT OF THE CLOUDS WILL BE GONE...WITH THE GREATEST COVERAGE OVER THE SW/SC MOUNTAINS. EXPECT MOST OF THE AREA TO BECOME CLEAR AND ALLOW TEMPS TO DROP OFF THE CLIFF. BUF POINTED OUT THAT A GOOD SMOKE LAYER IS HEADING AT US /MAINLY TO THE N OF PA/ FROM CANADA. THIS MAY SERVE TO KEEP TEMPS UP JUST SLIGHTLY TONIGHT...BUT WILL WEIGHT THE FORECAST ONLY VERY SLIGHTLY TO ACCOUNT FOR THIS POSSIBLE EFFECT. MOS GUIDANCE RARELY PUMPS OUT RECORD MINS AT ANY POINT...SO WHEN 2 OF OUR CLIMO SITES ARE GUIDED TOWARD REC MINS...THAT IS A STRONG SIGNAL FOR A SIGNIFICANT EVENT. THE SET UP IS NEARLY-PERFECT. HIGH PRESSURE MOVES OVERHEAD. HOWEVER...THE HIGH PRESSURES AND 8H TEMPS ARE NOT HIGHLY ANOMALOUS - JUST SLIGHTLY BELOW NORMAL. THE WIND SHOULD DIE DOWN TONIGHT AND THE CLOUDS DISSIPATE. WILL TAKE TEMPS DOWN TO WITHIN A DEG OR TWO EITHER SIDE OF RECORD MINS AT MANY PLACES TONIGHT. SEE THE CLIMO SECTION FOR THE CURRENT RECORD MINS. THE COLD TEMPS ARE A CLASSIC SCENARIO FOR FOG IN THE NRN VALLEYS. THE AIR WILL BE SO DRY THAT IT WILL MAKE IT TOUGH TO FOG IN. WILL GO AHEAD AND MENTION PATCHY FOG FOR NOW. THOSE COLD TEMPS IMMEDIATELY AROUND KBFD COULD ALSO CREATE SOME FROST IN THE OPEN AREAS. WILL ALSO MENTION PATCHY FROST BUT NOT GO ADVY BECAUSE OF THE LOW PROBABILITY OF WIDESPREAD COVERAGE AND THE ALREADY- TENUOUS TEMP FORECAST. && .SHORT TERM / FRIDAY THROUGH 6 AM FRIDAY/... AFTER THE CHILLY START...FRIDAY WILL SEE A GOOD RECOVERY IN TEMPS. SCT-BKN CLOUDS MAY SNEAK INTO THE NW EARLY IN THE DAY AND THEN THE COLD AIR OVERHEAD WILL ALLOW A FEW DIURNAL CU TO FORM. MAXES UNDER 12-14C 8H TEMPS WORKS OUT TO HIGHS IN THE L70S IN THE HIGHEST ELEVATIONS AND L80S IN THE EASTERN VALLEYS. && .LONG TERM /FRIDAY THROUGH THURSDAY/... OVERALL SCENARIO REMAINS UNCHANGED IN THE LONG TERM PERIOD AS A LARGE UPPER RIDGE BUILDING OVER THE FOUR CORNERS REGION IS FORECAST TO EXPAND NORTH AND EAST INTO THE ROCKIES AND PLAINS DURING THE PERIOD. DOWNSTREAM...THIS WILL LEAD TO MODERATE TO STRONG LONG WAVE TROFFING OVER THE EASTERN THIRD OF THE COUNTRY. UPPER LOW TO THE EAST OF HUDSON BAY WILL BE STRENGTHENED AT TIMES BY SHORTWAVE ENERGY IN THE STRONGER JET STREAM FLOW ACROSS CANADA. SOUTHWARD EXTENSION OF THIS LOW/TROF WILL AT TIMES DURING THE PERIOD STRENGTHENING THE TROFFING ACROSS THE NORTHEASTERN U.S./OUR REGION. THE TREND OF MEDIUM RANGE MODEL GUIDANCE IS FOR STRONGER/DEEPER TROFFING DOWNSTREAM ACROSS THE EASTERN U.S...DEVELOPING AN ALMOST FULL LATITUDE TROF EXTENDING FROM THE EASTERN CANADA LOW SWD TO FLORIDA. THIS WILL LIKELY SERVE TO EXPAND AND PROLONG THE CHANCES FOR PCPN THIS WEEKEND. A POTENTIALLY STRONGER SYSTEM /STRONGER THAN THE ONE THAT USHERED IN THE COOL AND MUCH LESS HUMID AIRMASS OVERNIGHT WEDNESDAY NIGHT/ WILL AFFECT THE REGION FOR THE SECOND HALF OF THE UPCOMING WEEKEND. THE TREND OF STRONGER TROUGHING MENTIONED ABOVE HAS LEAD TO SLOWER ARRIVAL AND DEPARTURE OF THE FRONTAL SYSTEM IN THE DAILY PROGS. THE ECMWF IN LATEST RUN HAS SLOWED UP THE PROGRESSION OF THIS UPPER LEVEL LOW...WHERE THE GFS OPERATIONAL AND ENSEMBLES HAVE SPED UP ITS PROGRESSION THROUGH THE GREAT LAKES REGION. A WARM FRONT WILL BE ON OUR WESTERN DOORSTEP LATE SATURDAY NIGHT AND SUNDAY...AS THE EC CONTINUES TO SLOW ITS PROGRESSION SO EXPECT THE WARM FRONT TO MOVE IN CLOSER TO MIDDAY SUNDAY. HAVE THUS ADJUSTED POPS/TIME. ASSOCIATED COLD FRONT DOES NOT CROSS THE STATE TIL MONDAY...WHERE SURPRISINGLY AT THIS POINT...THE EC AND GFS COME CLOSELY IN PHASE. THIS LARGE UPPER LEVEL LOW COULD BECOME QUASI STATIONARY OVER SOUTHERN CANADA...GREAT LAKES REGION WHICH COULD LEAD TO A POTENTIAL PROLONGED PERIOD OF SHOWERS AND THUNDERSTORM THROUGH THE MIDDLE OF NEXT WEEK. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... DIURNAL CU BEING HELPED ALONG BY WEAK SHORT WAVE TROUGH PUSHING SE THROUGH THE AREA AT 18Z. THIS FEATURE AND THE HEATING SHOULD BOTH BE GOING AWAY BY 00Z...AND CLOUDS WILL CONTINUE TO GET BIGGER BREAKS/DISSIPATE. BY OR SHORTLY AFTER SUNSET MOST OF THE CU WILL BE GONE. EXPECT VFR CONDITIONS AND LIGHT WINDS OVERNIGHT. ONLY THE NORTHERN VALLEYS WILL SEE THE USUAL VALLEY FOG FORM WITH SEASONALLY-COLD TEMPERATURES DIPPING TO WELL-BELOW THE STREAM/RIVER WATER TEMPS. HOWEVER...THE AIR IS PRETTY DRY AND HAVE KEPT MENTIONS OF FOG AWAY FROM ALL BUT KBFD. VFR EXPECTED FOR ALL OF FRIDAY AND INTO SATURDAY AS HIGH PRESSURE FLOATS OVERHEAD AND SLIDES TO THE EAST. HUMIDITY AND SCT TSRA WILL RETURN SAT AFTN/EVENING...BUT SUNDAY LOOKS WORSE FOR FLYING CONDITIONS WITH MORE-WIDESPREAD SH/TSRA IN ADVANCE OF A COLD FRONT. OUTLOOK... SAT...PATCHY AM VALLEY FOG N...OTHERWISE VFR. SCT PM TSRA/MVFR POSS W. SUN...SHRA/TSRA WITH WARM FRONT PASSAGE MON...MORE WIDESPREAD SHRA/TSRA WITH COLD FRONT PASSAGE. && .CLIMATE... MIN TEMP RECORDS FRIDAY MORNING JULY 25TH: BFD - 39 SET IN 2013 - NOT LONG AGO BUT SHORT PERIOD OF RECORD JST - 45 SET IN 1957 AOO - 48 SET IN 1957 IPT - 48 SET IN 1953 MDT - 53 SET IN 1953 && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DANGELO NEAR TERM...DANGELO SHORT TERM...DANGELO LONG TERM...LAMBERT/GARTNER AVIATION...DANGELO CLIMATE...DANGELO

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