Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 272056 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 356 PM EST TUE JAN 27 2015 .SYNOPSIS... A STRONG STORM SYSTEM EAST OF NEW ENGLAND TONIGHT WILL REACH THE CANADIAN MARITIMES ON WEDNESDAY. HIGH PRESSURE WILL MOVE IN FROM THE OHIO VALLEY WEDNESDAY AND SETTLE OVER THE REGION WEDNESDAY NIGHT AND THURSDAY MORNING. LOW PRESSURE WILL MOVE THRU THE GREAT LAKES ON THURSDAY AND REFORM EAST OF NEW ENGLAND ON FRIDAY. HIGH PRESSURE WILL MOVE IN FROM THE GREAT LAKES ON SATURDAY...FOLLOWED BY A LOW PRESSURE SYSTEM MOVING THROUGH THE APPALACHIANS EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... ALL WINTER STORM WARNINGS AND ADVISORIES WERE CANCELED EARLY THIS AFTERNOON. SOME SCATTERED SNOW SHOWERS OR FLURRIES ARE POSSIBLE EARLY THIS EVENING IN THE SOUTHERN POCONOS AND NORTHWEST NEW JERSEY...BUT ANY SUCH ACTIVITY IS EXPECTED TO END BEFORE MIDNIGHT. THE LOW PRESSURE SYSTEM RESPONSIBLE FOR THE WINTRY WEATHER THE PAST DAY OR SO WILL CONTINUE TO MOVE SLOWLY NORTHEAST OVERNIGHT...REACHING THE CANADIAN MARITIMES BY MORNING. SKIES ARE EXPECTED TO GRADUALLY CLEAR FROM WEST TO EAST DURING THE OVERNIGHT HOURS AS THIS LOW MOVES FURTHER AWAY. ON THE OTHER HAND, NORTHWEST WINDS IN THE 10 TO 20 MPH RANGE...WITH HIGHER GUSTS...WILL CONTINUE AS THE GRADIENT BETWEEN THIS LOW AND INCOMING HIGH PRESSURE FROM THE WEST PERSISTS INTO WEDNESDAY. ONCE THE CLOUDS CLEAR...THE FRESH SNOW COVER UP NORTH SHOULD ALLOW TEMPERATURES TO DROP INTO THE SINGLE DIGITS. LOWS IN THE MID-TEENS TO AROUND 20 ARE EXPECTED FURTHER SOUTH WERE THE SNOW COVER ISN/T AS DEEP OR WIDESPREAD. A BLEND OF MAV/MET GUIDANCE WAS USED FOR OVERNIGHT TEMPERATURES, UNDERCUT BY A DEGREE OR TWO UP NORTH TO ACCOUNT FOR SNOWCOVER. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... MOSTLY SUNNY CONDITIONS ARE EXPECTED...EXCEPT FOR MORNING CLOUDINESS IN NORTHERN NJ (LINGERING EFFECTS FROM THE DEPARTING LOW). NORTHWEST WINDS WILL PICKUP ONCE AGAIN AS DAYTIME MIXING TAKES PLACE...THEN GRADUALLY DECREASE LATE IN THE DAY AS THE SUN BEGINS TO SET AND AS THE PRESSURE GRADIENT CONTINUES TO DECREASE. TEMPS ARE EXPECTED TO MAX OUT IN THE LOW TO MID 20S FAR NORTH, AND IN THE LOW 30S SOUTH. AGAIN...A BLEND OF MAV/MET GUIDANCE WAS USED FOR HIGH TEMPERATURES WITH A SLIGHT CUT IN THE LOCATIONS OF DEEPER SNOWPACKS. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... THE MID LEVEL PATTERN AT 00Z THU IS COMPRISED OF A DEEP TROUGH AT 70W WITH A NORTHERN STREAM RIDGE ALONG THE BRITISH COLUMBIA COAST AND A SOUTHERN STREAM CLOSED LOW INVOF THE CALIFORNIA COAST. BETWEEN THESE TWO FEATURES...S/WV RIDGE WILL CREST OVER THE MID ATL ON THU...THEN NORTHERN AND SOUTHERN STREAM S/WV ENERGY IS PROGGED TO PHASE INVOF THE MISSISSIPPI VALLEY AND BECOME NEG TILTED AS IT REACHES 70W AROUND 00Z SAT. THIS LEADS TO LOW PRESSURE MOVING THRU THE GREAT LAKES ON THU WITH REDEVELOPMENT CURRENTLY MODELED INVOF GEORGES BANK ON FRI. BY SAT...NORTHERN STREAM S/WV ENERGY ENTERING THE NORTHERN PLAINS IS EXPECTED TO INTERACT WITH SOUTHERN STREAM S/WV ENERGY EJECTING OUT OF A CLOSED LOW INVOF THE FOUR CORNERS REGION. THIS LEADS TO A COMPLEX AREA OF LOW PRESSURE...WHICH IS CURRENTLY PROGGED TO MOVE THRU THE APPALACHIANS EARLY NEXT WEEK. THE BEST CHANCES FOR PRECIP IN THE LONG TERM WILL BE THU NIGHT INTO EARLY FRI AND THEN AGAIN EARLY NEXT WEEK...WITH PTYPE ISSUES LIKELY WITH BOTH SYSTEMS...AS TEMPERATURES ROLLER COASTER FROM NEAR NORMAL TO WELL BELOW NORMAL THROUGHOUT THE PERIOD. DETAILS... WED NIGHT AND THU... GENERALLY TRANQUIL WEATHER AS A RIDGE OF HIGH PRES CRESTS OVER THE REGION. EXPECTING IDEAL CONDITIONS FOR RADIATIONAL COOLING THU AM AS ATMOS DECOUPLES WITH CLEAR SKIES...LIGHT WINDS...AND FRESH SNOW COVER. EXPECTING MIN TEMPS 10 TO 15 DEGREES BELOW NORMAL REGION- WIDE. ON THU LARGE SCALE FLOW BECOMES SOUTHWEST AND MODEL X-SECS INDICATE MID LEVEL MOISTURE STREAMING INTO THE REGION...ESPECIALLY IN THE AFTN. THE GFS AND CANADIAN ARE MOST AGGRESSIVE IN BRINGING PRECIP IN PRIOR TO 00Z ALONG AND WEST OF THE DE RIVER...AND THIS TIMING IS REFLECTED IN THE FCSR. MAX TEMPS WILL GENERALLY BE 5 TO 10 DEGREES BELOW NORMAL. THU NIGHT THRU FRIDAY NIGHT... LOW PRESSURE MOVES THRU THE SAINT LAWRENCE VALLEY WITH GOOD MODEL AGREEMENT ON THE STRONGEST DYNAMICS JUST TO THE NORTH AND WEST... AND THUS RESULTANT QPF BULLSEYE. ATTM...MODEL QPF IS GENERALLY A TRACE OVER THE DELMARVA TO 0.2 INCHES OVER THE FAR NORTHWEST. THE GREATEST UNCERTAINTY IS IN MODEL THERMAL PROFILES AND THUS PTYPE. THIS DOES NOT APPEAR TO BE A COLD AIR DAMMING SITUATION WITH HIGH PRES OFFSHORE AND THE ABSENCE OF AN INVERSION. NEVERTHELESS...LOW PRES WELL NORTHWEST WILL LEAD TO BOUNDARY LAYER WINDS INSUFFICIENT FOR WARM AIR ADVECTION. MODEL SOUNDINGS INDICATE A RAIN/SNOW EVENT WITH CURRENT PROFILES CONFINING RAIN TO SOUTHEAST NJ...DE...AND MD WHERE MODEL QPF IS LIGHTEST. EXPECTING SNOW-LIQUID RATIOS RANGING FROM 5:1 TO 10:1 WHICH WOULD GIVE ACCUMULATIONS UP TO 1 INCH INVOF I-95 TO 3 INCHES OVER THE NORTHWEST...BUT THIS IS PRELIMINARY... STAY TUNED. PRECIP ENDS EARLY FRI WITH STRONG COLD AIR ADVECTION AS LOW PRESSURE REDEVELOPS EAST OF NEW ENG...AS TEMPS FALL THRU THE DAY AFTER MORNING MAXS. THERE IS ALSO THE POTENTIAL FOR SNOW SQUALLS...PARTICULARLY OVER THE POCONOS...WITH A COLD FRONTAL PASSAGE FRI AFTN. MODEL SOUNDINGS SHOW MIXING TO 850 HPA WITH POTENTIAL FOR WIND GUSTS AROUND 30 KNOTS. THE COMBINATION OF BLUSTERY WINDS AND BELOW NORMAL TEMPERATURES ON FRIDAY NIGHT WILL LEAD TO LOW WIND CHILLS...THEREFORE...A WIND CHILL ADVISORY MAY EVENTUALLY BE NEEDED. SAT AND SUN... MID-LEVEL CYCLONIC FLOW OVER THE REGION ON SAT GRADUALLY GIVES WAY TO BRIEF RIDGING ON SUN. ON SAT THE COLUMN WILL DRY OUT...ASIDE FOR POSSIBILITY OF STRATOCUMULUS BENEATH A MODELED SUBSIDENCE INVERSION...WITH ONE LAST BRISK DAY IN NORTHWEST FLOW BEHIND DEPARTING LOW. MID LEVEL FLOW ON SUNDAY BECOMES SOUTHWEST...AND THE COLUMN WILL GRADUALLY MOISTEN IN ADVANCE OF STORM SYSTEM TO THE SOUTHWEST. TEMPS EXPECTED TO BE 10 TO 15 DEGREES BELOW NORMAL. SUNDAY NIGHT THRU TUESDAY... COMPLICATED FORECAST AS LOW PRESSURE TRAVERSES THE APPALACHIANS LATE SUNDAY INTO EARLY MONDAY. STRONG MID-LEVEL VORT MAX APPROACHES THE COAST WITH DUAL JET SETUP FAVORING REDEVELOPMENT INVOF MID ATL OR NEW ENGLAND. ATTM...THERMAL PROFILES GENERALLY FAVOR SNOW WITH RAIN MIXING IN CLOSER TO THE COAST...BUT THIS IS HIGHLY UNCERTAIN. REDEVELOPMENT COULD LEAD TO COLDER AIR BEING DRAWN IN...WHICH WOULD BRING SNOW FURTHER SOUTH ALONG THE COAST. ANY WINTER WX WOULD BE EXACERBATED BY COLD ANTECEDENT CONDITIONS...MAKING SURFACES MORE PRONE TO ICING. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. CONDITIONS HAVE GRADUALLY IMPROVED TO VFR AND SKIES WILL TRANSITION TO BROKEN AND SCATTERED THROUGHOUT THE EVENING. NORTHWEST WIND GUSTS AROUND 20 KNOTS WILL CONTINUE AT ALL TAF SITES. FOR TONIGHT THERE IS POTENTIAL FOR SOME SCATTERED LOW CLOUDS AROUND 2,000 FEET TO FORM. HOWEVER, WITH CONTINUED NORTHWEST WINDS OVER 10 KNOTS THERE IS LITTLE TO MODERATE CONFIDENCE THIS WILL OCCUR. WEDNESDAY WILL BE A VFR DAY WITH NORTHWEST GUSTS AGAIN AROUND 20 KNOTS. SOME HIGHER GUSTS ARE POSSIBLE IN THE AFTERNOON. GUSTS WILL AGAIN DECREASE AFTER SUNSET. OUTLOOK... WEDNESDAY NIGHT...PRIMARILY VFR. THURSDAY INTO FRIDAY MORNING...PRIMARILY VFR FOR MUCH OF THU. LIGHT SNOW IS EXPECTED TO OVERSPREAD THE AREA FROM WEST TO EAST THU NIGHT BUT MAY REACH ABE/RDG BY LATE AFTERNOON. MVFR/IFR POSSIBLE WITH THE SNOW. HIGHEST CONFIDENCE IS AT NORTHERN TERMINALS. FRIDAY AFTERNOON...VFR WITH NW WINDS GUSTING AROUND 30 KT. FRI NIGHT...VFR WITH GUSTY NW WINDS EXPECTED TO CONTINUE. SATURDAY...VFR. SUNDAY...LIGHT SNOW IS EXPECTED TO OVERSPREAD THE AREA FROM WEST TO EAST DURING THE DAY...LOW CONFIDENCE ON TIMING. MVFR/IFR POSSIBLE WITH THE SNOW. && .MARINE... GALE WIND GUSTS HAVE TAPERED OFF IN CONJUNCTION WITH THE DEPARTING LOW PRESSURE SYSTEM. HOWEVER, ON THE BACKSIDE OF THE LOW PRESSURE STRONG NORTHWEST WINDS WITH SCA GUSTS WILL LIKELY CONTINUE TILL AROUND 18Z WEDNESDAY IN ALL MARINE ZONES, WITH SOME SCATTERED SCA GUSTS THROUGH 23Z. WAVE HEIGHTS WILL GRADUALLY DECREASE BY WEDNESDAY AFTERNOON TO AROUND FIVE FEET. WE HAVE CANCELLED THE REMAINDER OF THE GALE WARNING AND REPLACED WITH A SCA THROUGH 23Z WEDNESDAY, ENDING EARLIER ON THE BAY. OUTLOOK... WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...NO MARINE HEADLINES ARE ANTICIPATED. SOME FREEZING SPRAY POSSIBLE WEDNESDAY NIGHT. FRIDAY...NEAR GALE-FORCE NW GUSTS BEHIND DEPARTING LOW PRESSURE. FRIDAY NIGHT...POSSIBLE LEFTOVER NW GALE FORCE GUSTS. FREEZING SPRAY LIKELY. SATURDAY...SCA CONDITIONS POSSIBLE. FREEZING SPRAY POSSIBLE... ESPECIALLY EARLY. SUNDAY...CONDITIONS ARE EXPECTED TO REMAIN BELOW SCA THRESHOLDS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...GALE WARNING UNTIL 6 PM EST THIS EVENING FOR ANZ430-431- 450>455. && $$ SYNOPSIS...FRANCK NEAR TERM...MIKETTA SHORT TERM...MIKETTA LONG TERM...FRANCK AVIATION...FRANCK/GAINES MARINE...FRANCK/GAINES

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