Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 162202 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 602 PM EDT THU APR 16 2015 .SYNOPSIS... LOW PRESSURE EAST OF THE CAROLINA COAST TONIGHT WILL BE PUSHED OUT TO SEA BY A WEAK COLD FRONT MOVING THROUGH OUR AREA ON FRIDAY NIGHT. A STRONGER COLD FRONTAL PASSAGE WILL OCCUR SATURDAY AFTERNOON. HIGH PRESSURE WILL BRIEFLY MOVE IN FROM THE NORTH ON SUNDAY. LOW PRESSURE IS THEN EXPECTED TO STALL OVER THE GREAT LAKES REGION NEXT WEEK... LEADING TO A COLD FRONTAL PASSAGE MONDAY NIGHT...WITH ANOTHER COLD FRONTAL PASSAGE POSSIBLE ON WEDNESDAY OR THURSDAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... WITH THIS ESTF UPDATE NOT TOO MANY CHANGES WERE MADE. BASED ON RADAR IMAGERY, SFC OBS WITH MEASURABLE AND RECENT HRRR/RAP RUNS, WE LOWERED MEASURABLE POPS FOR MOST OF THIS EVENING. LOOKS LIKE DC AREA PCPN IS MAINLY SPRINKLES WITH DECENT SHOWERS IN WESTERN PA AT LEAST INITIALLY SHOULD BY-PASS OUR CWA. SLIGHT TEMP ADJUSTMENTS MADE BASED ON CURRENT READINGS. SURFACE HIGH PRESSURE HAS SHIFTED SOUTHEAST FROM NEW ENGLAND AND IS NOW EAST OF OUR AREA...WITH A RIDGE AXIS EXTENDING SOUTHWEST ACROSS THE MID-ATLANTIC REGION. THIS HAS ALLOWED SFC WINDS TO VEER AROUND TO THE SOUTHEAST IN THE COASTAL ZONES AND MORE SOUTHERLY FARTHER INLAND. SKIES HAVE BEEN MOSTLY SUNNY THIS AFTERNOON...EXCEPT FOR SOME CIRRUS...WHICH HAS ALLOWED INLAND TEMPS TO RISE TO THE UPPER 60S MOST AREAS. COASTAL AREAS ARE SOMEWHAT COOLER DUE TO ONSHORE FLOW FROM THE OCEAN WATER WHERE TEMPS ARE STILL IN THE 40S. SURFACE WINDS TONIGHT WILL SLACK OFF A BIT WHILE REMAINING SLY... BUT WINDS AT 850 MB WILL BECOME SOUTHWEST AND INCREASE TO 30-35 KT. THUS LOW-LEVEL MOISTURE WILL BE ON THE INCREASE. MID LEVEL CLOUDS ARE ALREADY PRESENT TO OUR WEST FROM WESTERN PA SOUTH INTO VA. THESE WILL BE SPREADING EAST ACROSS THE AREA THIS EVENING AND CONTINUE TO THICKEN OVERNIGHT. BY LATE TONIGHT SHOWERS ARE EXPECTED TO DEVELOP AHEAD OF A SHORTWV TROF MOVING EAST FROM THE GRTLKS/OHIO VLY. OVERNIGHT POPS GENERALLY INCREASE FROM CHANCE ALONG THE COAST TO LIKELY IN THE FAR NORTHWEST. THE INCREASING CLOUD COVER WILL ALSO KEEP OVERNIGHT MIN TEMPS CONSIDERABLY WARMER THAN LAST NIGHT. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... SCATTERED SHOWERS ARE EXPECTED TO CONTINUE ACROSS THE AREA FRIDAY MORNING WITH A TENDENCY TO SPREAD FARTHER SOUTHEAST INTO SOUTH NJ AND NORTHERN DELMARVA. SKIES WILL BE CLOUDY IN THE MORNING BUT PARTIAL CLEARING IS EXPECTED IN THE AFTERNOON AS DEEPER MOISTURE MOVES OFF TO THE EAST. A FEW HUNDRED J/KG OF CAPE ARE FCST TO DEVELOP IN THE AFTERNOON ALONG WITH LOW-LVL CONVERGENCE ALONG A SURFACE TROF...THUS WE HAVE MAINTAINED A CHANCE OF SHOWERS AND ADDED SOME ISOLD T-STORMS AS WELL. MAX TEMPS FRIDAY AFTERNOON COULD BE A COUPLE OF DEGREES WARMER THAN TODAY...GIVEN ENOUGH SUN AND A SLIGHTLY WARMER AIR MASS. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... OVERVIEW... THE FAIRLY PROGRESSIVE MID-LEVEL PATTERN OVER THE PAST 7+ DAYS WILL GRADUALLY BECOME MORE BLOCKY THROUGH NEXT WEEK. A GENERAL SOUTHERN STREAM REX BLOCK WILL BE PARKED INVOF THE CA COAST...AS A HIGH AMPLITUDE NORTHERN STREAM RIDGE BUILDS INTO THE WESTERN CONUS. MEANWHILE...A S/WV CURRENTLY OVER THE GULF OF ALASKA WILL TRAVERSE THIS RIDGE AND DIVE SOUTHEASTWARD INTO THE UPPER MS VALLEY...HEIGHT FALLS WITH THIS FEATURE WILL BE SUFFICIENT TO EJECT A CLOSED FOUR- CORNERS LOW NEWD. THE COMBINATION OF THE RIDGE BUILDING INTO THE WESTERN CONUS AND STRONG DOWNSTREAM BLOCKING DEVELOPING OVER THE NORTH ATLANTIC WILL LEAD TO A DEEP CLOSED LOW OVER THE UPPER MS VALLEY DURING THE EARLY-MID NEXT WEEK. OVERALL...GENERALLY FAIR WEATHER THIS WEEKEND WILL BECOME MORE ACTIVE DURING THE MON THRU THU TIME FRAME. IN PARTICULAR...LOW PRESSURE MOVING THROUGH THE GREAT LAKES EARLY NEXT WEEK WILL LEAD TO REDEVELOPMENT ALONG THE MID-ATLANTIC COASTLINE...WITH HEAVY RAIN AND GUSTY WINDS POSSIBLE IN THE MON-TUE TIME FRAME. THEREAFTER...WITH THE UPPER LOW TO THE NORTHWEST...UNSETTLED WEATHER IS PROBABLE THRU AT LEAST THURSDAY. DALIES... FRI NIGHT...LINGERING SHOWERS AND POSSIBLE THUNDER WITH A WEAK COLD FRONTAL PASSAGE EARLY. BEST CHANCE OF THUNDER IS OVER THE DELMARVA AND FAR SOUTH JERSEY. SYNOPTIC SETUP AND MODEL SOUNDINGS INDICATE THE POTENTIAL FOR PATCHY FOG IF ENOUGH CLEARING TAKES PLACE. SAT...OVERALL A NICE DAY. A STRONGER BUT DRY COLD FROPA IS EXPECTED DURING THE DAY. SUN...HIGH PRESSURE BUILDS IN. EXPECTING A DRY DAY WITH SOME MID TO HIGH LEVEL CLOUDS STREAMING IN FROM THE SOUTHWEST. FLOW WILL BECOME ONSHORE SO COASTAL LOCALS WILL BE COOLER. MONDAY AND TUESDAY...LOW PRESSURE MOVING THROUGH THE GRT LAKES WILL REDEVELOP TO SOME EXTENT OFF THE MID-ATLANTIC COAST. GOOD KINEMATICS AND THERMODYNAMICS ARE IN PLACE FOR THE POSSIBILITY OF SOME HEAVIER RAIN DURING THE MON NIGHT THRU TUESDAY MORNING TIME FRAME. SUPPORTING THIS...PRECIPITABLE WATER VALUES APPROACH 1.5 INCHES...WHICH IS +2 STANDARD DEVIATIONS ABOVE NORMAL FOR THE MONTH OF APRIL. THIS SYSTEM MAY ALSO MOVE SOMEWHAT SLOWER THAN CURRENTLY MODELED...WHICH WOULD INCREASE RAINFALL VALUES AS WELL. IT/S TOUGH TO SAY WHETHER WE MAKE IT INTO THE WARM SECTOR...BUT AT LEAST ELEVATED CONVECTION POSSIBLE PER MODEL STABILITY INDICES. GUSTY SE WINDS ALONG THE COAST. WED AND THU...WITH A DEEP CLOSED LOW TO OUR WEST AND CYCLONIC FLOW ALOFT...EXPECT GENERALLY UNSETTLED WEATHER TO CONTINUE DURING THIS PERIOD. && .AVIATION /22Z THURSDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. WINDS THIS AFTERNOON HAVE VEERED TO THE SE FOR NEAR COASTAL AREAS AND MORE TO THE S OR EVEN SW FARTHER INLAND. THIS HAS OCCURRED IN RESPONSE TO SFC HIGH PRES SLIDING SEWD OFF OF NEW ENGLAND. SOUTH WINDS BETWEEN 5 AND 1O KT WILL CONT OVER NIGHT. CLOUDS WILL ALSO BE INCREASING BUT VFR CONDS SHOULD CONTINUE UNTIL WELL AFTER MIDNIGHT. CIGS ARE EXPECTED TO LOWER TO MVFR SHORTLY BEFORE SUNRISE FRIDAY MORN. CIGS AND VSBYS MAY BE LOCALLY LOWER MVFR OR BRIEFLY IFR IN SCATTERED SHOWERS TOMORROW MORNING. CONDS SHOULD GRADUALLY IMPROVE DURG THE AFTN BUT THERE IS ALSO A CHANCE FOR SCT TSTMS. OUTLOOK... SAT NIGHT...MVFR IN SHRA AND LOW CLOUDS GRADUALLY IMPROVING TO VFR WITH THE PASSAGE OF A COLD FRONT. ISOLATED THUNDER IS ALSO POSSIBLE PRIOR TO THE FROPA. GROUND FOG MAY DEVELOP TOWARD DAYBREAK LEADING TO MVFR CONDITIONS OVER THE INTERIOR. SUN...MVFR IN GROUND FOG POSSIBLE EARLY. OTHERWISE...VFR CONDITIONS. MON AND TUE...MVFR/IFR IN LOW CLOUDS...SHRA AND FOG ACROSS THE AREA. GUSTY SOUTHEAST WINDS MAY ALSO LEAD TO LLWS. && .MARINE... SUB SCA CONDS ARE EXPECTED THROUGH TONIGHT AND FRIDAY. SWLY WINDS AND ASSOCD SEAS SHOULD INCREASE SOME ON FRIDAY BUT STILL REMAIN BELOW SCA CONDS. SLY WINDS TONIGHT WILL BRING INCREASINGLY WARMER AND MOIST AIR OVER THE COLD WATER WHICH COULD RESULT IN AREAS OF FOG. VSBY ON FRIDAY COULD BE LOCALLY POOR IN SCT SHOWERS AND ISOLD TSTMS. OUTLOOK... SAT AND SAT NIGHT...SCA MAY BE NEEDED IN POST-FRONTAL GUSTY NW FLOW. SUN...SUB-SCA CONDITIONS EXPECTED. MON AND TUE...SOUTHEAST WINDS MAY REACH SCA LEVELS. CONSIDERABLE UNCERTAINTY DUE TO ULTIMATE TRACK AND STRENGTH OF LOW PRESSURE. COOL SEA SURFACE TEMPERATURES MAY ALSO LEAD TO AN INVERSION WITH STRONGER WINDS REMAINING ALOFT. && .FIRE WEATHER... A STRONGER BUT DRY COLD FROPA IS EXPECTED ON SATURDAY. THIS WILL LEAD TO VERY DRY CONDITIONS ALONG WITH GUSTY NORTHWEST WINDS. GIVEN NO HEAVY QPF IN THE FCST LEADING UP TO SATURDAY...AS WELL AS LOW SFC RELH AND THE GUSTY WINDS...CONDITIONS MAY BE CLOSE TO RED FLAG CRITERIA DURING THE DAY ON SAT. AGAIN THIS IS DEPENDENT ON THE FUEL MOISTURE AND ANTECEDENT RAINFALL. && .TIDES/COASTAL FLOODING... TIDES WILL NEED MONITORING FOR POTENTIAL MINOR COASTAL FLOODING ISSUES AS POSITIVE DEPARTURES INCREASE SUNDAY THROUGH MONDAY NIGHT WITH DEVELOPING ONSHORE FLOW. THIS WILL OCCUR IN CONJUNCTION WITH A NEW MOON THIS WEEKEND SO ASTRONOMICAL TIDES WILL ALREADY BE HIGH. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...FRANCK NEAR TERM...AMC/GIGI SHORT TERM...AMC LONG TERM...FRANCK AVIATION...AMC/FRANCK MARINE...AMC/FRANCK FIRE WEATHER... TIDES/COASTAL FLOODING...

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