Area Forecast Discussion
Issued by NWS State College, PA

Current Version | Previous Version | Text Only | 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
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KCTP 240309 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1009 PM EST FRI JAN 23 2015 .SYNOPSIS...
-- Changed Discussion --
LOW PRESSURE WILL MOVE QUICKLY NORTHEAST TO THE DELMARVA COAST BY EARLY SATURDAY MORNING...BEFORE PASSING EAST OF NEW ENGLAND SATURDAY NIGHT. THIS STORM WILL BRING A BRIEF BUT MODERATE TO HEAVY SNOWFALL TO THE SOUTHEAST HALF OF PENNSYLVANIA. ANOTHER LOW PRESSURE AREA...IN THE FORM OF AN ALBERTA CLIPPER WILL TRACK JUST SOUTH OF PENNSYLVANIA SUNDAY NIGHT. AN UPPER LVL TROUGH WILL REMAIN OVER THE NORTHEAST CONUS THRU THE REST OF THE WEEK.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 10 AM SATURDAY MORNING/...
-- Changed Discussion --
1000 PM... THE ONLY TWEAKS TO MAKE ARE WITH AN EYE TOWARD THE NAM/HRRR/RAP WHICH ALL PORTRAY A BIT OF A DRY SLOT - AS FORSEEN BY THE DAYSHIFT - WHICH WILL LIKELY DROP SNOW/PRECIP INTENSITY FROM SOUTH TO NORTH STARTING EVEN BEFORE SUNRISE...MAYBE EVEN BY 4-5AM...OVER FRANKLIN CO/SC MTNS. ALL PRECIP MAY END AN HOUR OR TWO FASTER ELSEWHERE IF THE NEWEST HIGH-RES GUIDANCE IS ON TOP OF THINGS. THE LATEST IS NOT ALWAYS THE GREATEST...THOUGH. SO SMALL CHANGES ARE ALL THAT WILL BE MADE. HAVE LOWERED POPS A BIT IN THE SC COS...BUT LEFT THEM AT LIKELY OR BETTER LATE TONIGHT AND EARLY SAT. REALLY HIGH RETURNS ON LWX RADAR JUST TO THE S OF THE MD BORDER ARE MOST LIKELY A MIX OR HEAVY SNOW PER OBS AND DUAL POL HINTS. SO SNOW TOTALS SHOULD BE IN FAIRLY GOOD SHAPE. JUST A SMALL TWEAK DOWNWARD IN THE SRN PARTS OF THE AREA ARE ALL THAT WERE MADE FOR THIS UPDATE...BUT ALL THE WARNINGS AND ADVYS WILL CONTINUE AS IS...SINCE THE CHANGES DID NOT DROP ANY AREA OFF THEIR RESPECTIVE PLATFORMS. 640 PM... RAIN/SNOW ON THE DOORSTEP JUDGING BY OBS AND INCREASING RADAR ECHOES ON THE MD BORDER. TEMPS ALONG THERE ARE M30S...SO IT COULD START AS RAIN OR SNOW. BUT THE EVAP COOLING PROCESS WILL TURN IT TO SNOW AS THE LOWER ATMOS MOISTENS UP. MILD SRLY WIND IN MD/VA COULD STILL LIFT SOME MILDER AIR INTO THE AREA AND PROLONG THE RAIN CHCS THRU THE NIGHT...AND THIS ALREADY IN THE FCST. PREV... MID AFTERNOON SATELLITE LOOP SHOWS THICKENING CLOUD SHIELD RACING INTO OUR AREA FROM THE SW...AHEAD OF A POTENT SOUTHERN STREAM TROUGH AND IT/S ASSOCIATED...GRADUALLY STRENGTHENING SFC LOW /1007 MB/ CENTERED NEAR KPNS. EXPECT THE CLOUD BASES TO LOWER TO AN ALTOSTRATUS...7-10 KFT AGL BY 22Z ACROSS THE SOUTH...AND DURING THE EARLY EVENING HOURS NORTH OF INTERSTATE 80. WINDS FOR THE REST OF TODAY/EARLY TONIGHT WILL BE LIGHT AND GRADUALLY BACK THROUGH THE SOUTH...THEN TO THE SE OR EAST. TEMPS FOR THE REST OF THE DAYLIGHT HOURS WILL BE IN THE MID 20S ACROSS THE NORTH...AND LOWER TO MID 30S AS YOU HEAD SOUTH ACRS CENTRAL AND SRN PENN. 09Z SREF AND 12Z U.S. OPER MODEL CONSENSUS POINTS TWD A SWATH OF SIGNIFICANT/HEAVY SNOWFALL OCCURRING NEAR AND A FEW LAYERS OF COUNTIES TO THE NORTHWEST OF I-81 TONIGHT AND SAT MORNING...WITH THE SLIGHTLY SUB-1000 MB SFC LOW ANTICIPATED TO TRACK ACROSS THE SRN DELMARVA PENINSULA BETWEEN 10-12Z SATURDAY. MADE JUST SOME MINOR UPWARD MODIFICATIONS TO SNOWFALL ACROSS THE COUNTIES NEAR THE ALLEGHENY FRONT...AND SLIGHTLY TRIMMED AMOUNTS NEAR KTHV AND KLNS...WHERE A TRANSITION TO LIGHTER INTENSITY PRECIP /SNOW...RAIN OR FREEZING RAIN/ MAY OCCUR EARLY SATURDAY AS SUBSIDENCE OCCURS IN ASSOCIATION WITH THE NEWD DEPARTURE OF THE HIGHER SEEDER-FEEDER CLOUDS...AND PASSAGE OF THE UNFAVORABLE LEFT ENTRANCE REGION OF A 140 KT UPPER JET. AN ADVISORY TYPE SNOWFALL OF 3-5 INCHES STILL APPEARS HIGHLY LIKELY TONIGHT INTO EARLY SAT JUST TO THE SE OF THE ALLEGHENY FRONT IN CENTRAL PENN /AND ACROSS THE FAR SE/ WHILE LOW END...WINTER STORM WARNING AMOUNTS OF 6-8 INCHES SHOULD FALL ACROSS THE BULK OF THE REGION BETWEEN I-81 AND THE I99/ROUTE 22O CORRIDOR. NO OTHER CHANGES/ADDITIONS MADE TO THE WARNING AND ADVISORY AREAS WITH THIS MID AFTERNOON UPDATE. RADAR AND LATEST HIGH RES MODEL DATA ALL POINT TOWARD SNOW ARRIVING ACROSS THE S TIER ARND 00Z AND REACHING IT/S FURTHEST WESTWARD EXTENT ACROSS THE NW MTNS BY ARND MIDNIGHT. 12Z MDL BLENDED QPF /AND MEDIAN VALUES ON THE 09Z SREF/ RANGES FROM PRACTICALLY NOTHING OVR WARREN CO...TO 0.3 TO 0.5 INCHES ACROSS THE LAURELS...CENTRAL MTNS...AND MIDDLE SUSQ VALLEY...TO PERHAPS 0.75 INCHES NEAR THE I-81 CORRIDOR. THE PASSAGE OF SOUTHERLY LL JET LATE TONIGHT WILL DRAW MILDER AIR INTO FAR SE PA...LIKELY MIXING OR CHANGING THE PTYPE TO EITHER LIGHTER RAIN OR -FZRA FOR UP TO SEVERAL FROM ARND KLNS SOUTH AND EASTWARD. STILL...EXPECT SEVERAL INCHES OF ACCUM BEFORE ANY CHANGEOVER ACROSS THE SE. FURTHER NORTH...SNOW/WATER RATIOS LOOK TO BE ARND 12/1...TYPICAL FOR COASTAL STORMS.
-- End Changed Discussion --
&& .SHORT TERM /10 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... BY DAWN SATURDAY...LL JET AND BEST ISENTROPIC LIFT SHOULD HAVE SHIFTED EAST OF THE REGION. HOWEVER...LIGHTER /TO BRIEFLY MDT/ SNOW /ASSOC WITH MID LVL SHORTWAVE AND LINGERING 850-700 MB DEFORMATION BAND/ IS LIKELY TO LAST THRU ARND MIDDAY...AND PERHAPS A BIT LONGER OVR THE NE COUNTIES. NW FLOW IN WAKE OF THIS SYSTEM SHOULD BRING PARTIAL CLEARING LATE TO EASTERN PA. HOWEVER...A FAST MOVING AND WEAK CLIPPER TYPE SHORTWAVE WILL BE DIVING INTO THE REGION FROM THE GRT LKS TOWARD EVENING...LIKELY PRODUCING -SHSN ACROSS THE ALLEGHENY PLATEAU SAT EVENING. THE AIR MASS BEHIND TONIGHT/S LOW IS NOT PARTICULARLY COLD AND ENS MEAN 925 TEMPS SUPPORT HIGHS SATURDAY IN THE M/U30S OVR MUCH OF THE AREA...WHICH SHOULD RESULT IN MUCH IMPROVED ROAD CONDS BY SAT AFTN. && .LONG TERM /SUNDAY THROUGH FRIDAY/... TROFFY NW FLOW PATTERN WILL PERSIST THROUGH MUCH OF THE PERIOD IN THE WAKE OF THE EARLY WEEKEND STORM. THIS WILL LEAD TO LIMITED OPPORTUNITIES FOR PHASING WITH ANY SRN STREAM ENERGY. MED RANGE MDLS ALL TRACKING A POTENT ALBERTA CLIPPER JUST SOUTH OF PA SUN NIGHT. LATEST TRENDS ARE FARTHER SOUTH ON THE TRACK AND HAVE BACKED OFF ON QPF AND THUS SNOW TOTALS. PLENTY OF COLD AIR AVAILABLE AND EXPECT NO PRECIP TYPE ISSUES WITH THIS EVENT. AS THE LOW INTENSIFIES OFF THE THE ATLANTIC COAST ON MONDAY...WE COULD SEE LIGHT SNOW/SHOWERS CONTINUING THROUGH THE DAY WITH TEMPERATURES REMAINING STEADY OR SLOWLY FALLING THROUGH THE 20S. COLDEST AIR OF THE WEEK DIVES IN BEHIND THE DEPARTING SYSTEM ON TUESDAY WITH STATEWIDE HIGHS A FEW DEGREES EITHER SIDE OF 20F. SUB-ZERO LOWS POSSIBLE ACROSS A GOOD PART OF CENTRAL PA TUESDAY...AS SFC HIGH BUILDS OVR THE AREA. CLEARING SKIES...A CALM WIND AND FRESH SNOW COVER COULD RESULT IN AN IDEAL RADIATIONAL COOLING SCENARIO. MODERATING CHILL IS IN STORE FOR THE MID TO LATE WEEK...AS RIDGING AT THE SURFACE AND ALOFT MOVES IN AHEAD OF NEXT IN SERIES OF ALBERTA CLIPPERS. ANOTHER POTENT SHORTWAVE WILL BRING A COLD FRONT THROUGH THE REGION THUR NIGHT INTO FRIDAY WITH MAIN SCATTERED SNOW SHOWERS. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... SNOW IS SLOWLY SPREADING NORTHWARD AND IS ONLY STARTED TO SNOW THROUGH THE SOUTHERN HALF OF PENNSYLVANIA. SNOW WILL OVERSPREAD THE REMAINDER OF THE AREA BY LATE EVENING. THE SNOW WILL BE ACCOMPANIED BY LOWERING CIGS/VSBYS WITH MAJORITY OF TERMINALS DROPPING TO IFR BY MID EVENING AND LINGERING THROUGH MUCH OF THE OVERNIGHT. SOME FREEZING RAIN LIKELY WORKS INTO THE SOUTHERN MTNS AND LOWER SUSQ AFTER MIDNIGHT...WHICH COULD BRING ICING ISSUES. ANY PRECIPITATION WILL WEAKEN AND TAPER OFF MID TO LATE SATURDAY MORNING...WITH AREAS CLEARING AS WINDS SHIFT TO THE WEST NORTHWEST...SATURDAY AFTERNOON. EXPECT CIGS AND VSBYS TO LIFT THROUGH THIS TIMEFRAME. AS A MORE NORTHWESTERLY FLOW TAKES HOLD...WINDS WILL BECOME BREEZY WITH CONDITIONS ONCE AGAIN DROPPING TOMORROW NIGHT AT BFD AND JST...BEGINNING BETWEEN 22Z TO 02Z. OUTLOOK... SUN...VFR INTO THE AFTERNOON...THEN SNOW DEVELOPING ACROSS THE WEST IN THE AFTERNOON OR EVENING...AND OVERSPREADING ALL OF CENTRAL PENN AND THE SUSQ VALLEY AT NIGHT. MON...AM SNOW WITH WIDESPREAD MVFR TO IFR LIKELY. TUE...NO SIG WEATHER EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 1 PM EST SATURDAY FOR PAZ019-024- 025-033-042-045-046-064>066. WINTER STORM WARNING UNTIL 1 PM EST SATURDAY FOR PAZ026>028- 034>036-049>053-056>059-063. && $$ SYNOPSIS...LAMBERT NEAR TERM...DANGELO/LAMBERT SHORT TERM...LAMBERT LONG TERM...FITZGERALD/GARTNER AVIATION...LAMBERT/CERU

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