Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 181731 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 131 PM EDT SAT APR 18 2015 .SYNOPSIS... A COLD FRONT WILL CROSS THE TRI-STATE LATE THIS AFTERNOON AND EARLY THIS EVENING. HIGH PRESSURE THEN BUILDS OVER THE AREA INTO SUNDAY AND MOVES OFFSHORE SUNDAY AFTERNOON AND NIGHT. A WARM FRONT NEARS THE AREA ON MONDAY...WITH A WAVE OF LOW PRESSURE RIDING ALONG THE FRONT PASSING NEAR OR OVER THE AREA MONDAY NIGHT. THIS WILL BE FOLLOWED BY A COLD FRONTAL PASSAGE FROM LATE MONDAY NIGHT INTO TUESDAY MORNING. A SERIES OF WEAK COLD FRONTS AND/OR TROUGHS OF LOW PRESSURES WILL MOVE THROUGH DURING THE MIDWEEK PERIOD FOLLOWED BY HIGH PRESSURE AT THE END OF THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... MINOR CHANGES WERE MADE THIS UPDATE TO REFLECT THE LATEST TRENDS IN OBSERVATIONS AND GUIDANCE. WEAK 700-500 HPA SHORTWAVE PASSES TO THE N/NE INTO THIS AFTERNOON...WITH STRENGTHENING WNW-NW LOW LEVEL FLOW AS A RESULT. STILL ON TRACK TO HAVE THE WARMEST DAY OF THE YEAR SO FAR DUE TO THE COMBINATION OF A MAINLY SUNNY SKY...DEEP MIXING...850 MB TEMPS RANGING FROM 7-10C...AND DOWNSLOPING WNW LOW FLOW...INCREASING TO 15-25KT IN THE AFTERNOON - STRONGEST FAR N AND FAR W ZONES. HIGHS WILL RUN AROUND 15-20 DEGREES AROUND NORMAL...IT WOULD NOT BE SURPRISING IF A FEW LOCATIONS IN NE NJ/NYC/LOWER HUDSON VALLEY REACHED OR BROKE THE 80 DEGREE MARK. BASED ON LATEST TRENDS SHOWING TEMPERATURES RUNNING A FEW DEGREES ABOVE FORECAST...DID TWEAK HIGHS UP A FEW DEGREES AT MOST LOCATIONS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... COLD FRONT MOVES ACROSS THE REGION THIS EVENING. WINDS MAY INCREASE TO 15-20 MPH WITH 20-30 MPH WITH ITS PASSAGE...BUT WINDS DIMINISH AS THE EVENING PROGRESSES...AND WINDS WILL SHIFT TO THE NORTH AT 5-10 MPH BY MIDNIGHT TONIGHT. THE FRONT SHOULD COME THROUGH DRY...WITH THE EXCEPTION OF SOME MID-LEVEL CLOUDS WITH ITS PASSAGE. HIGH PRES OVER EASTERN CANADA WILL DROP INTO THE GULF OF MAINE WITH THE CENTER OF THE HIGH JUST EAST OF CAPE COD ON SUNDAY. AS A RESULT...WINDS WILL SHIFT TO THE SOUTHEAST...USHERING A MUCH COOLER AND MORE SEASONAL AIRMASS INTO THE REGION. HIGHS ON SUNDAY WILL TOP OFF IN THE MID 50S TO LOW 60S...EXCEPT FOR LONG ISLAND AND COASTAL CT...WHERE HIGHS WILL ONLY BE IN THE LOW 50S. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... AN AMPLIFYING FULL LATITUDE TROF WILL LIFT NORTH AND EAST ACROSS THE GREAT LAKES AND INTO THE NE SUN NIGHT INTO TUE. THIS WILL RESULT IN AN APPROACHING FRONTAL SYSTEM THAT WILL HAVE BOTH ATLANTIC AND GULF MOISTURE TO WORK WITH. PRECIPITABLE WATERS VALUES WILL BE ON THE ORDER OF 2SD ABOVE NORMAL. THE 00Z GLOBAL MODELS HAVE SPED UP THE TIMING OF THIS SYSTEM BY A LITTLE...BUT STILL SOME DIFFERENCES REGARDING PLACEMENT OF HIGHER RAIN AMOUNTS. A FRONTAL WAVE IS FORECAST TO PASS OVER OR NEARBY JUST THE AREA MON NIGHT...IN ESSENCE KEEPING THE AREA NEARBY DECENT LIFT. LIFT WILL BE ENHANCED...ESPECIALLY OVER THE EASTERN HALF OF THE CWA...BY FRONTOGENETIC FORCING AND A 50-60 KT SE LOW LEVEL JET LATE SUN NIGHT INTO EARLY MON MORNING. THINKING IS THAT EASTERN ZONES WILL PROBABLY END UP WITH HIGHER RAIN AMOUNTS IN GENERAL. INSTABILITY ALOFT COULD ALSO RESULT IN SOME ISOLATED ELEVATED THUNDER MON NIGHT...WHICH WOULD ADD TO THE VARIABILITY AND SOME UNCERTAINTY WITH THE HIGHEST RAIN AMOUNTS FOR THE TRI STATE AREA. RAINFALL AMOUNTS OF 1 TO 1.5 INCHES ARE FORECAST...WITH THE HIGHEST AMOUNTS OVER LONG ISLAND AND CT. UP TO 2 INCHES LOCALLY IS STILL POSSIBLE. THE SE FLOW PROBABLY ENHANCES OROGRAPHIC LIFT...SO FORECAST AMOUNTS NW OF THE CITY COULD BE A LITTLE TOO LOW. SO IN GENERAL...RAIN BECOMES LIKELY LATE SUNDAY NIGHT FOR MOST SPOTS...WITH MODERATE TO POTENTIALLY BRIEFLY HEAVY RAIN MONDAY MORNING. MID LEVELS DRY OUT MONDAY AFTERNOON...SO LIGHT RAINFALL OR POSSIBLY EVEN DRIZZLE WOULD BE EXPECTED BY LATE IN THE DAY. LIGHT RAIN REMAINS LIKELY MONDAY NIGHT AS A WEAK LOW PRESSURE WAVE CENTER MOVES THROUGH. SOME FOG DEVELOPMENT EXPECTED MON NIGHT AS WELL WITH WINDS BECOMING LIGHTER AND PLENTY OF MOISTURE AROUND. GUSTS UP TO 25 TO 30 MPH WILL POSSIBLE AT THE SFC ON MON...BUT TEMP PROFILES WILL BE INVERTED LIMITING ANY STRONGER WINDS FROM COMING DOWN. CONDITIONS DRY OUT TUE INTO WED WITH A SERIES OF WEAK FRONTS AND/OR TROUGHS MOVING ACROSS THE REGION. THESE WILL REINFORCE A SEASONABLE AIRMASS. HIGH PRESSURE THEN FOLLOWS FOR THE END OF THE WEEK. UPPER AIR PATTERN WILL BE DOMINATED BY A BROAD...FLAT TROUGH EAST OF THE MS RIVER VALLEY. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... A COLD FRONT PASSES EAST THIS EVENING FOLLOWED BY HIGH PRESSURE BUILDING OVER THE TERMINALS THROUGH SUNDAY MORNING. VFR THRU THE TAF PERIOD. WNW WINDS WILL INCREASE THIS AFTERNOON TO 10 TO 15 KT WITH GUSTS AROUND 20 KT. THE EXCEPTION WILL BE SW SEA BREEZES AT KJFK/KISP/KBDR/KGON. KJFK WILL LIKELY SHIFT TO THE SOUTH LATE THIS AFTERNOON WITH GUSTS TO 25 KT. WINDS WILL SHIFT TO THE NW THIS EVENING WITH GUSTS AROUND 20 KT. GUSTS END BY 06Z...WITH WINDS VEERING TO THE NE 7 TO 12 KT. NE WINDS CONTINUE SUNDAY MORNING. .OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY... .SUN AFTERNOON...VFR. SE WIND G15-20KT POSSIBLE. .SUN NIGHT...MVFR/IFR IN RAIN. LLWS DEVELOPING LATE. ESE WIND G20-25KT LATE. .MON...MVFR/IFR IN RAIN. LLWS EARLY. ESE WIND G25-30KT. .TUE...MVFR BECOMING VFR. WEST G25KT. .WED-THU...VFR. && .MARINE... MINOR CHANGES WERE MADE THIS UPDATE TO REFLECT THE LATEST TRENDS IN OBSERVATIONS AND GUIDANCE. THE FORECAST APPEARS ON TRACK. A COLD FRONT APPROACHES THE WATERS LATER THIS AFTERNOON AND MOVES ACROSS THIS EVENING. GENERALLY SUB-SCA CONDITIONS...BUT A FEW NEARSHORE GUSTS TO 25 KT ARE POSSIBLE THIS AFTERNOON. HIGH PRESSURE BUILDS EAST OF THE WATERS LATE SUN AFT WITH AN APPROACHING FRONTAL SYSTEM FROM THE WEST. THIS WILL RESULT IN A STRENGTHENING SE FLOW SUN NIGHT INTO MON WITH SCA CONDITIONS LIKELY ACROSS ALL WATERS. SEAS WILL BUILD TO 7 TO 10 FT ON MON...THEN WILL BE SLOW TO SUBSIDE MON NIGHT INTO TUE. SUB-SCA CONDITIONS ARE EXPECTED ACROSS THE REMAINING WATERS LATE MON NIGHT INTO WED. && .FIRE WEATHER... DRY WEATHER...MINIMUM RH 20-30 PERCENT...AND WINDS GUSTING TO 25-30 MPH WILL LEAD TO ELEVATED POTENTIAL FOR FIRE GROWTH/SPREAD LATER THIS AFTERNOON AND EARLY THIS EVENING. APPEARS WIND GUSTS WILL NOT INCREASE UNTIL 3 OR 4PM...BUT NOT WORTH CHANGING TIMING OF HEADLINES AT THIS STAGE. GUSTS MAY BRIEFLY STRENGTHEN AFTER THE COLD FRONTAL PASSAGE AS WELL. A RED FLAG WARNING IS IN EFFECT FOR THE WHOLE CWA THROUGH 8 PM GIVEN EXPECTED WEATHER CONDITIONS. && .HYDROLOGY... THERE IS THE POTENTIAL FOR SIGNIFICANT RAINFALL WITH AN APPROACHING FRONTAL SYSTEM MONDAY INTO MONDAY NIGHT. STORM TOTAL RAINFALL WITH THIS SYSTEM WILL BE FROM 1 TO 1.5 INCHES...WITH THE HIGHEST AMOUNTS GENERALLY OVER LONG ISLAND AND CT. LOCALIZED HIGHER AMOUNTS WILL BE POSSIBLE. FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEB SITE. && .TIDES/COASTAL FLOODING... A PROLONGED PERIOD OF SE FLOW LATE SUN NIGHT INTO MON EVE WILL LIKELY RESULT IN WIDESPREAD MINOR COASTAL FLOODING. ASTRONOMICAL HIGH TIDES WILL BE RUNNING HIGH FOLLOWING A NEW MOON ON SAT. IN SOME CASES...DEPARTURES OF ONLY HALF A FOOT ABOVE NORMAL ARE NEEDED. STORM SURGE IS LIKELY TO PRODUCE WATERS LEVELS 1 TO 1 1/2 FT ABOVE NORMAL. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR CTZ005>012. NY...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR NYZ067>075- 078>081-176>179. NJ...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR NJZ002-004- 006-103>108. MARINE...NONE. && $$ SYNOPSIS...JC/MPS NEAR TERM...MALOIT SHORT TERM...MPS LONG TERM...JC/DW AVIATION...DS MARINE...JC/MALOIT/MPS FIRE WEATHER... HYDROLOGY...JC/MPS TIDES/COASTAL FLOODING...

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