Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 200438 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1238 AM EDT MON OCT 20 2014 .SYNOPSIS... HIGH PRESSURE BUILDS TO THE SOUTH THIS MORNING...THEN OFF THE MID ATLANTIC COAST LATER TODAY. LOW PRESSURE WILL THEN APPROACH FROM THE GREAT LAKES TONIGHT. SECONDARY LOW PRESSURE DEVELOPS NEAR THE MID-ATLANTIC COAST BY LATE TUESDAY...THEN SLOWLY MEANDERS TO THE GULF OF MAINE BY FRIDAY MORNING...THEN TO THE CANADIAN MARITIME PROVINCES BY SATURDAY MORNING. A COLD FRONT APPROACHES FROM THE NORTHWEST SATURDAY...THEN CROSSES THE AREA SATURDAY NIGHT. HIGH PRESSURE BUILDS IN FROM SOUTH CENTRAL CANADA SUNDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... MEAN TROF RESIDES ACROSS THE EASTERN U.S. AS IT ONCE AGAIN WILL RELOAD WITH SHORT WAVE ENERGY ACROSS THE UPPER MIDWEST...CARVING OUT ANOTHER AMPLIFIED TROF ACROSS THE GREAT LAKES AND OHIO VALLEY STATES BY TONIGHT. PRIOR TO THAT TIME...RIDGING BOTH ALOFT AND AT THE SFC MOVES INTO THE AREA THIS MORNING. WINDS WILL DIMINISH WITH THE APPROACH OF THE HIGH. THE COMBINATION OF A LIGHT W/NW FLOW LATE...MAINLY CLEAR SKIES...AND A DRY AIR MASS WILL ALLOW INTERIOR LOCATIONS TO DROP TO AROUND FREEZING AND MOST OTHER LOCATIONS OUTSIDE OF METRO NY INTO THE UPPER 30S. FREEZE WARNINGS AND FROST ADVISORIES REMAIN UP FOR MOST LOCATIONS WITH THE EXCEPTION OF NYC METRO AND WESTERN LI. THE AVERAGE FIRST AUTUMN FREEZE IS OCTOBER 21 FOR THE INTERIOR...SO THIS RIGHT ON TIME FROM A CLIMATOLOGICAL PERSPECTIVE. MOST LOCATIONS WILL BE ABOUT 5 TO 10 DEGREES BELOW NORMAL. THE MAIN FORECAST CHALLENGE THOUGH REMAINS THE AMOUNT OF HIGH CLOUDS PRECLUDING SFC HEAT TO RADIATE...AND THE AIR MASS PERHAPS BEING JUST DRY ENOUGH TO LIMIT FROST FORMATION. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/... HIGH PRESSURE WILL MOVE OFF THE MID ATLANTIC COAST TODAY WITH A RETURN SW FLOW...WHILE LOW PRESSURE DROPS SE ACROSS THE GREAT LAKES. THERE IS SOME UNCERTAINTY WITH THE OPAQUENESS OF THE MID AND HIGH LEVEL CLOUDS AND THE AMOUNT OF SUN FILTERING THROUGH. CONDITIONS WILL LIKELY START OFF PARTLY TO MOSTLY SUNNY...BUT BECOME MOSTLY CLOUDY LATE AS MID LEVEL CLOUDS FILTER IN FROM THE WEST. HIGHS WILL BE A TOUCH WARMER WITH A SW FLOW...BUT A SUBSIDENCE INVERSION WILL INHIBIT DEEP MIXING...WITH HIGH ONLY IN THE MID AND UPPER 50S. FOR TONIGHT...WEAK LIFT AND DEEPENING MOISTURE MAY RESULT IN SOME SHOWER ACTIVITY AFTER MIDNIGHT. RAINFALL AMOUNTS WILL BE LIGHT. HEIGHTS BEGIN TO FALL LATE AT NIGHT IN RESPONSE TO THE APPROACHING LONGWAVE TROF TO THE WEST. LOWS WILL BE CONSIDERABLY WARMER DUE TO THE CLOUD COVER AND SW FLOW...WITH MOST LOCATIONS 45 TO 50. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... MODELS START OUT IN SOLID AGREEMENT ON OVERALL PATTERN...AND MOST DETAILS ON TUESDAY...BUT THEN BEGIN TO DIVERGE LATTER IN THE WEEK...ESPECIALLY ON THE HANDLING OF SYSTEMS TO THE WEST OF THE CUTOFF LOW THAT EXITS TO OUR NORTHEAST LATE THIS WEEK. USED A BLEND OF ALL AVAILABLE GUIDANCE THROUGH FRIDAY NIGHT...THEN LEANED TOWARDS THE ECMWF FOR SATURDAY THROUGH SUNDAY. I USED THIS BLEND LATE IN THE PERIOD DUE TO THE ECMWF BETTER RUN TO RUN CONSISTENCY...THE GEFS ENSEMBLES SUPPORTING A LESS PROGRESSIVE PATTERN...ESPECIALLY WITH REGARDS TO THE LARGE AMPLITUDE RIDGE TO OUR WEST...AND BETTER HISTORICAL VERIFICATION OF THE ECMWF IN THIS TIME FRAME. THE WEATHER WILL BE UNSETTLED FROM TUESDAY INTO AT LEAST FRIDAY AS A CUTOFF LOW INITIALLY TRACKS TO OUR S...THEN MEANDERS NEAR US DURING THE MIDDLE OF THE WEEK...THEN SLOWLY LIFTS TO THE NORTHEAST TO THE CANADIAN MARITIMES BY THE WEEKEND. HOWEVER...WITH THE CUTOFF LOW SO CLOSE TO THE REGION...WOULD NOT EXPECT CONTINUOUS PRECIPITATION DURING THIS TIME FRAME. ISENTROPIC LIFT OF ANY SIGNIFICANCE APPEARS TO HOLD OFF UNTIL TUESDAY NIGHT...SO ONLY FORECASTING A CHANCE OF SHOWERS ON TUESDAY - EXCEPT LIKELY W 1/3 OF CWA CLOSER TO CLOSED LOW. THEN HAVE RAIN LIKELY TUESDAY NIGHT-WEDNESDAY IN RESPONSE TO DECENT ISENTROPIC LIFT - ULTIMATELY WILL LIKELY END UP BEING PERIODS OF RAIN IN THIS TIME FRAME...LINGERING LIKELY POPS INTO WEDNESDAY NIGHT AS BEST ISENTROPIC LIFT TRANSITIONS EAST WITH FORECAST TRACK OF SURFACE LOW. HAVE LIKELY POPS ON THURSDAY ACROSS NORTHERN ZONE IN RESPONSE TO LIKELY LOCATION OF DEFORMATION AXIS AS CLOSED LOW BEGINS TO LIFT TO THE NE. THEN LINGER CHANCE POPS INTO FRIDAY AS THE LOW LIFTS FARTHER NE. FOR NOW GOING DRY FRIDAY NIGHT-SUNDAY...AS APPEARS WILL BE LIMITED LOW LEVEL MOISTURE AVAILABLE FOR PASSING COLD FRONT/NORTHERN STREAM TROUGH TO ACT ON SATURDAY NIGHT...WITH WEAK RIDGING AHEAD OF THE TROUGH. SHOULD THEN HAVE A DRY NW FLOW ON THE BACKSIDE OF THE TROUGH. FOR HIGHS ON TUESDAY USED A BLEND OF MAV/MET/ECS GUIDANCE WITH NAM 2-METER TEMPERATURES AND A MIX DOWN FROM 925-875 HPA PER BUFKIT SOUNDINGS. EXPECT HIGHS TO BE NEAR TO SLIGHTLY ABOVE NORMAL. A BLEND OF MAV AND MET GUIDANCE WITH NAM 2-METER TEMPERATURES WAS USED FOR LOWS TUESDAY NIGHT WITH READINGS FORECAST TO BE 5 TO 10 DEGREES ABOVE NORMAL. ON WEDNESDAY A BLEND OF MEX/MEN/EKD/ECE/ECM/WPC GUIDANCE WITH NAM 2-METER TEMPERATURES AND A MIX DOWN FROM 950 HPA PER BUFKIT SOUNDINGS WAS USED FOR HIGHS. EXPECT VALUES TO BE AROUND 5 DEGREES BELOW NORMAL. FROM WEDNESDAY NIGHT THROUGH SUNDAY A BLEND OF MEX/MEN/EKD/ECE/ECM/WPC GUIDANCE WAS USED FOR TEMPERATURES. LOWS WILL RUN SLIGHTLY ABOVE NORMAL IN THIS TIME FRAME...AND AFTER SLIGHTLY BELOW NORMAL HIGHS ON THURSDAY...HIGHS WILL RUN NEAR TO SLIGHTLY ABOVE NORMAL AS WELL FRIDAY THROUGH SUNDAY. IT SHOULD BE NOTED THAT HIGHS ON SUNDAY COULD END UP BEING SOME 5-10 DEGREES COLDER THAN FORECAST IF THE ECMWF VERIFIES - IN RESPONSE TO SHALLOW LOW LEVEL COLD ADVECTION BEHIND THE COLD FRONT. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... HIGH PRESSURE OVER THE TERMINALS REMAINS THROUGH THE OVERNIGHT AND THEN MOVES OFF THE MID ATLANTIC COAST MONDAY MORNING. LOW PRESSURE APPROACHES FROM THE NORTHWEST MONDAY AFTERNOON WITH A WARM FRONT MOVING THROUGH LATE IN THE DAY. VFR. THERE COULD BE SOME SPRINKLES WEST OF THE TERMINALS LATE IN THE DAY. NORTHWEST WIND LESS THAN 10 KT BACKS TO WEST OVERNIGHT. THE WIND CONTINUES TO BACK TO THE SOUTHWEST MONDAY MORNING AND THEN WILL BE NEARLY SOUTHERLY LATE IN THE AFTERNOON. SPEEDS INCREASE TO AROUND 10 KT DURING THE DAY. .OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY... .MONDAY NIGHT THROUGH THURSDAY...MVFR OR LOWER CONDS IN RAIN. BEST CHANCES TUESDAY THROUGH WEDNESDAY. .FRIDAY...IMPROVING CONDS. NW WINDS 15-20 KT WITH 20-25 KT GUSTS. && .MARINE... AS WINDS DIMINISH...CONDITIONS WILL IMPROVE ACROSS THE WATERS EARLY THIS MORNING. HIGH PRESSURE BUILDS IN FROM THE WEST WITH A DIMINISHING NW FLOW...AND SWELLS FROM DISTANT HURRICANE GONZALO CONTINUE TO DIMINISH. HIGH PRESSURE WILL THEN PASS OFF THE MID ATLANTIC COAST TODAY WITH A RETURN SW FLOW. CONDITIONS ARE FORECAST TO REMAIN BELOW SCA CRITERIA THROUGH THE DAY AND INTO TONIGHT. SUB-SMALL CRAFT CONDITIONS ARE MOST LIKELY ON ALL WATERS TUESDAY THROUGH FRIDAY. WIND GUSTS SHOULD BE AROUND 20 KT FROM WEDNESDAY INTO THURSDAY NIGHT...AND COULD POSSIBLY REACH 25 KT MAINLY ON THE COASTAL OCEAN WATERS IN THIS TIME FRAME. ALSO...SEAS ON THE COASTAL OCEAN WATERS EAST OF MORICHES INLET COULD REACH 5 FT ON WEDNESDAY...AND POSSIBLY ON THE REMAINDER OF THE COASTAL OCEAN WATERS FROM WEDNESDAY NIGHT INTO THURSDAY NIGHT. FOR NOW THERE IS TOO MUCH UNCERTAINTY TO FORECAST SMALL CRAFT CONDITIONS DURING THE MIDDLE OF THE WEEK..EXCEPT FOR THE SCA LEVEL SEAS EAST OF MORICHES INLET ON WEDNESDAY. && .HYDROLOGY... THERE IS THE POTENTIAL FOR AROUND AN INCH OF RAIN FROM TUESDAY INTO THURSDAY. BECAUSE THIS WILL BE SPREAD OVER AROUND 48 HOURS...THERE DOES NOT APPEAR TO BE AN SIGNIFICANT HYDROLOGIC IMPACT EXPECTED AT THIS TIME. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR CTZ009>012. FREEZE WARNING UNTIL 8 AM EDT THIS MORNING FOR CTZ005>008. NY...FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR NYZ069-070- 079>081. FREEZE WARNING UNTIL 8 AM EDT THIS MORNING FOR NYZ067-068. NJ...FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR NJZ004-103-105- 107. FREEZE WARNING UNTIL 8 AM EDT THIS MORNING FOR NJZ002. MARINE...SMALL CRAFT ADVISORY UNTIL 5 AM EDT EARLY THIS MORNING FOR ANZ350-353. && $$ SYNOPSIS...MALOIT/DW NEAR TERM...JM/DW/PW SHORT TERM...DW LONG TERM...MALOIT AVIATION...MET MARINE...MALOIT/DW/PW HYDROLOGY...MALOIT/DW

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