Area Forecast Discussion
Issued by NWS State College, PA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KCTP 191953 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 353 PM EDT SUN APR 19 2015 .SYNOPSIS... A WARM FRONT AND UPPER LEVEL DISTURBANCE APPROACHING FROM THE TENNESSEE VALLEY WILL BRING A SOAKING RAIN TO THE REGION TONIGHT AND EARLY MONDAY. ADDITIONAL SHOWERS AND SCATTERED STRONG...TO POTENTIALLY SEVERE THUNDERSTORMS WILL DEVELOP ALONG AND AHEAD OF A COLD FRONT AS IT PUSHES EAST ACROSS THE STATE MONDAY AFTERNOON AND EVENING. A LARGE UPPER LEVEL LOW WILL SET UP OVER ONTARIO AND QUEBEC FOR THE MIDDLE AND LATTER PART OF THE WEEK...USHERING IN UNSEASONABLY COOL AIR WHICH WILL LAST INTO THE WEEKEND OR LONGER. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... THE DECENT AMOUNT OF SUNSHINE THROUGH HIGH CLOUDS SO FAR TODAY HAS HELPED TO BOOST TEMPS INTO THE LOWER AND MIDDLE 60S ACROSS THE NRN AND WRN HIGH TERRAIN...WITH MID 60S IN MOST OF THE CENTRAL VALLEYS...AND UPPER 60S THROUGHOUT PORTIONS OF THE SUSQ VALLEY. THICKENING MID AND HIGH CLOUDS WILL STREAM IN QUICKLY FROM THE SW DURING THE MID TO LATE AFTERNOON HOURS TODAY...WITH THE ONSET OF RAIN OCCURRING ABOUT 2 TO 3 HOURS AFTER THE THICKER MID DECK ARRIVES. LATEST MODEL TIMING OF THE LEADING...NE EDGE OF STRATIFORM RAIN SHIELD /INCLUDING THE 12Z NAM...09Z SREF...AND LATEST 16Z HRRR RUN/ SUGGESTS THAT ALL OF THE REGION /EXCEPT FOR THE LAUREL HIGHLANDS/ WILL BE DRY FOR THE REST OF THE DAYLIGHT HOURS. FAR SOUTHWESTERN AREAS WILL LIKELY SEE THE RAIN BEGIN AROUND 5-6PM /21-22Z/...WHILE THE ONSET OF RAIN MOVES TO NEAR A KBFD...TO KUNV AND KMRB LINE AROUND 01-02Z MONDAY...THEN ACROSS THE SUSQ VALLEY BETWEEN 03Z-05Z MONDAY. A STEADY SOAKING RAIN IS IN STORE FOR MUCH OF TONIGHT AS THE AXIS OF A HIGHLY ANOMALOUS /APPROX 4 SIGMA/ SOUTHERLY LLJ SLIDES NE ACROSS THE REGION...WITH PWATS OF 1-1.5 INCHES FALLING IN THE PLUS 2-3 SIGMA RANGE. THE BEST CHANCE FOR OVER 1 INCH OF RAIN TONIGHT WILL BE FOUND ACROSS THE CENTRAL AND SCENT MTNS. HIGHEST PROBABILITY OF THE 1 INCH/12 HOURS WILL BE ACROSS THE LAURELS AND SOUTHERN TIER COUNTIES. THERE/S ACTUALLY A SMALL AREA OF LOW PROBABILITY FOR UP TO 2 INCHES ALONG THE EASTERN SLOPES AND CREST OF THE LAURELS. IF RAINFALL AMTS DO REACH 2 INCHES IN THAT 12 HOUR PERIOD...THERE COULD BE SOME SMALL STREAM...MAINLY MINOR FLOODING CONCERNS. TEMPS THROUGHOUT THE NIGHT TONIGHT WILL BE 7-10F ABOVE NORMAL...WITH MINS EARLY MONDAY IN THE MID 40S TO LOWER 50S. SOUTHEAST SFC WINDS WILL BE GUSTY AS AN AXIS OF 60-70 KT S-SE WIND IN THE 3-5 KFT AGL LAYER MOVES EAST ACROSS THE REGION. TYPICALLY MOST RESIDENTS OF CENTRAL DO NOT GET MUCH IN THE WAY OF STRONG WIND GUSTS DURING STABLE SERLY FLOW RAIN EVENTS. HOWEVER...SOME BORDERLINE WIND GUSTS OF 40 TO 45 MPH WILL BE POSSIBLE ON THE RIDGE TOPS...AND JUST TO THE NORTH OF THESE HIGHER RIDGE-LINES /AND GAPS IN THOSE SAME RIDGES/. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... THE STEADY STRATIFORM...WARM FRONTAL RAINS GRADUALLY TAPER OFF THEN END FOR A WHILE DURING THE MID TO LATE MORNING HOURS. THE WARM FRONT WILL LINGER ACROSS THE CENTRAL MTNS AND LOWER TO MID SUSQ VALLEY MONDAY AFTERNOON AND EARLY EVENING. HOWEVER...THE STRONG LOW AND MID LEVEL FLOW AND APPROACHING STRONG COLD FRONT /AND LEFT EXIT REGION OF AN UPPER LEVEL JETLET/ WILL COMBINE WITH THE 1-1.5 INCH PWATS TO TRIGGER ADDITIONAL TSRA MON AFTERNOON AND EVENING. ADDITIONAL RAINFALL AMOUNTS FROM THIS CONVECTION WILL AVERAGE 0.25 TO 0.50. THE POTENTIAL EXISTS FOR SKIES TO AT LEAST PARTIALLY CLEAR DURING PEAK HEATING MONDAY ACROSS SOUTHERN PENN. SHOULD THIS OCCUR... MANY CONVECTIVE AND SHEAR PARAMETERS /NEAR AND JUST SOUTH OF THE QUASI STNRY FRONT/ ACROSS SCENT PENN AND THE MIDDLE-LOWER SUSQ VALLEY WILL COMBINE TO BRING THE POTENTIAL FOR SVR TSRA. THE MAIN SVR THREAT WILL BE ISOLATED LARGE HAIL AND LOCALIZED DAMAGING STRAIGHT-LINE WIND GUSTS. HOWEVER...WITH EHI/S IN THE 2-4 M2/S2 RANGE NEAR THE I-81 CORRIDOR BETWEEN 19Z MONDAY AND 00Z TUESDAY...THE POTENTIAL EXISTS FOR SOME SUPERCELLS AND ONE OR TWO TORNADOES CLOSE TO THE FRONTAL BOUNDARY. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... THE PATTERN WILL BE DOMINATED BY A LARGE UPPER LEVEL LOW MOVING THROUGH THE NORTHERN GREAT LAKES...AND THROUGH SOUTHERN CANADA MIDWEEK TO THE WEEKEND. THERE IS GOOD MODEL CONSENSUS THROUGH THE MID RANGE PERIOD. AFTER THE FRONT LIFTS OUT BY TUESDAY MORNING THE UPPER LOW HANGS AROUND S CANADA/NEW ENGLAND FOR SEVERAL DAYS KEEPING FAIRLY BRISK W/NW FLOW ACROSS PA. THIS WILL BRING A STEADY STREAM OF COLDER AIR AS TEMPS SLOWLY SLIP A BIT LOWER EACH DAY WITH BELOW NORMAL READINGS FOR A SEVERAL DAY PERIOD LINGERING INTO NEXT WEEKEND. PROXIMITY OF UPPER LOW WILL ALSO KEEP MENTION OF SCT SHOWERS IN THE FORECAST. A SHORTWAVE SHOULD DROP THROUGH THE REGION WEDNESDAY AFTERNOON INTO THURSDAY MORNING. THIS COULD DROP EVEN COLDER AIR INTO THE REGION BRINGING THE POSSIBILITY OF SNOW TO THE NW TO THE CENTRAL REGIONS OF PA. THE MODELS THEN DIVERGE ON A SOLUTION BUT THE UPPER LEVEL LOW SHOULD CONTINUE ITS EASTWARD TREK...WITH ONLY A SLIGHT CHANCE FOR PRECIPITATION NEXT WEEKEND. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... VFR CONDITIONS WILL PREVAIL FOR THE REST OF THE DAY ACROSS CENTRAL AND EASTERN SECTIONS OF THE CWA...BUT WILL QUICKLY DETERIORATE FROM SOUTHWEST TO NORTHEAST /LATE TODAY ACROSS THE LAURELS/ AND TONIGHT ELSEWHERE. EXPECT RESTRICTIONS TO REACH THE FIRST CENTRAL PENNSYLVANIA AIRFIELDS AROUND 00Z MONDAY /KJST/...THEN ALONG A KBFD TO KUNV AND KMDT LINE BETWEEN 02Z AND 04Z MONDAY. TIGHTENING PRESSURE GRADIENT LATE TODAY AND TONIGHT AHEAD OF AN APPROACHING COLD FRONT WILL PRODUCE GUSTY SOUTHEASTERLY WINDS...AND LOW LEVEL WIND SHEAR CONDITIONS. THE WIND SHEAR WILL END DURING THE EARLY TO MID MORNING HOURS MONDAY FROM WEST TO EAST ACROSS THE STATE...AS THE CORE OF THE STRONGEST WINDS LIFTS NE INTO NEW YORK STATE. ALL TAF SITES CONTAIN LLWS TONIGHT. RAIN AND WIDESPREAD IFR TO LIFR EXPECTED TONIGHT INTO MONDAY...BEFORE THE PRECIPITATION BECOMES MORE SHOWERY WITH THE APPROACH OF THE FRONT LATE MONDAY MORNING AND MONDAY AFTERNOON. THIS COLD FRONT WILL ALSO INTRODUCE THE CHANCE OF THUNDERSTORMS MONDAY TO THE ENTIRE REGION...WITH SOME POTENTIALLY STRONG TO SVR /ESP ACROSS CENTRAL AND SERN PENN WHERE A QUASI-STNRY FRONT WILL RESIDE PRIOR TO THE ARRIVAL OF THE LATE DAY COLD FRONT/. OUTLOOK... MON...WIDESPREAD RESTRICTIONS IN RAIN EARLY...SOME IMPROVEMENT IN THE AFTERNOON...BUT SCTD TSRA AND BRIEF RESTRICTIONS WILL DEVELOP FOR THE MID AFTERNOON AND EVENING HOURS. TUE- THU...UNSETTLED WITH NW FLOW EACH DAY...WITH AREAS OF RESTRICTED CIGS/VSBYS IN SHRA IN THE WESTERN AND NORTHERN MOUNTAINS...SPOTTY RESTRICTIONS IN MORE SCATTERED SHRA IN CENTRAL MOUNTAINS...AND MAINLY VFR IN THE EAST AND SOUTHEAST. && .FIRE WEATHER... SFC WIND FROM THE SOUTHEAST WILL BE 10-15 KTS WITH GUSTS AROUND 20KT ACROSS THE HIGHER TERRAIN OF SOUTHERN AND WESTERN PENN FOR THE REST OF THIS AFTERNOON...WHILE THE WIND STAYS A BIT LIGHTER ACROSS THE NE HALF OF THE STATE - WHERE REL HUMIDITY IS EXPECTED TO DIP TO/STAY BELOW 30 PERCENT FOR THE REST OF THE AFTERNOON. GUSTS OF 15 TO 20 MPH ARE POSSIBLE IN THE NORTHEAST BY LATE AFTERNOON. BUT THE GUSTS OVER 20MPH WILL ONLY MATCH UP WITH THE LOW RH/S FOR AN HOUR OR TWO AT THE MOST AND ONLY IN A SMALL PORTION OF THE NORTHERN MOUNTAINS. THE TIMEFRAME OF OPTIMAL CONDITIONS FOR FIRE SPREAD IS VERY NARROW...AND WILL NOT WARRANT A RED FLAG WARNING. A SIGNIFICANT...LOCALLY HEAVY RAINFALL IS EXPECTED STARTING THIS EVENING AND LASTING UNTIL A WARM FRONT LIFTS NE TONIGHT...THEN A COLD FRONT PUSHES EAST THROUGH THE STATE MONDAY AFTERNOON AND EVENING. COOLER TEMPERATURES FOR THE REST OF THE WEEK WILL LIKELY LEAD TO HIGHER RH/S AND KEEP FIRE WEATHER CONDITIONS BELOW CRITICAL. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...CERU/RXR AVIATION...JUNG/LAMBERT FIRE WEATHER...

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.