Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 272043 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 443 PM EDT SUN JUL 27 2014 .SYNOPSIS... A STRENGTHENING LOW PRESSURE SYSTEM WILL APPROACH THE REGION TONIGHT AND THEN TRACK THROUGH NEW ENGLAND ON MONDAY AS THE COLD FRONT MOVES ACROSS THE LOCAL AREA. COLD FRONT PUSHES EAST MONDAY NIGHT...SETTLING WELL OFFSHORE THROUGH THE MIDDLE OF THE WEEK AS HIGH PRESSURE BUILDS IN THE WAKE. LOW PRESSURE APPROACHES AGAIN FOR NEXT WEEKEND. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... CONVECTIVE COVERAGE THROUGH THE EVENING WILL BE QUITE ISOLATED DESPITE MARGINAL TO MODERATE INSTABILITY...DUE TO WEAK SUBSIDENCE AND EVEN A BIT OF MID- LEVEL CAPPING IN WAKE OF EARLIER SHORTWAVE. ANYTHING THAT DOES DEVELOPS HAS POTENTIAL TO BE STRONG TO SEVERE...WITH SHEAR/INSTABILITY LEVELS SUPPORTIVE...BUT AGAIN AN ISOLATED THREAT. MAIN CONCERN IS FOR TONIGHT AS A STRONG JET STREAK/POTENT SHORTWAVE AND STRENGTHENING SFC LOW/PRE-FRONTAL TROUGH APPROACHING TONIGHT...WITH ANOTHER ROUND OF SHRA/TSTMS EXPECTED OVERNIGHT. THE STRONG FORCING AND A MODERATE DEEP/LOW LEVEL SHEAR ENVIRONMENT ARE FAVORABLE FOR SEVERE WEATHER INTO THE OVERNIGHT...BUT THE LIMITING FACTOR WILL BE AMOUNT OF INSTABILITY REMAINING OVERNIGHT. AT LEAST ELEVATED MARGINAL INSTABILITY IS EXPECTED OVERNIGHT...BUT WITH UNSEASONABLY STRONG LLJ THIS COULD APPROACH/REMAIN NEAR MODERATE LEVELS. LOW/CAPE HIGH SHEAR ENVIRONMENTS ARE USUALLY NOT FAVORABLE FOR WIDESPREAD SEVERE WEATHER COVERAGE...BUT WITH STRONG FORCING AND IF LLJ CAN MAINTAIN HIGHER INSTABILITY A MORE WIDESPREAD SEVERE EVENT IS POSSIBLE. THE MAIN FOCUS FOR CONVECTION AFFECTING OUR AREA TONIGHT WILL BE ALONG AN APPROACHING PRE-FRONTAL TROUGH. WOULD EXPECT AT LEAST SCATTERED COVERAGE OF STORMS OR LINE SEGMENTS ALONG THIS BOUNDARY...BUT IF INSTABILITY REMAINS HIGHER...COVERAGE WOULD INCREASE AND COULD TAKE THE FORM OF A QLCS. MAIN THREAT WITH ANY LINE SEGMENT OR QLCS WILL BE DAMAGING WINDS AND HEAVY RAIN...WITH SUFFICIENT LOW-LEVEL SHEAR/HELICITY FOR STORM ROTATION AND A LOW PROB OF A TORNADO. DISCRETE CELLS HAVE POTENTIAL TO ROTATE AND PRODUCE LARGE HAIL AS WELL...BUT LOW CAPE/HIGH SHEAR ENVIRONMENTS ARE NOT FAVORABLE FOR HAIL...SO THIS IS A LOW THREAT. SO LOOKING FOR COVERAGE TO INCREASE SLIGHTLY THIS EVENING FROM NYC METRO AND POINTS N&W AS BETTER JET/SHORTWAVE ENERGY APPROACH...BUT MAIN ACTIVITY WITH PRE-FRONTAL TROUGH LIKELY OCCURS AFTER MIDNIGHT FROM NYC METRO AND POINTS WEST...AND AFTER 2-3 AM INTO LI/CT. AS THE LOW TRACKS INTO SOUTHERN NEW ENGLAND LATE TONIGHT INTO EARLY MONDAY MORNING...THE PRE-FRONTAL TROUGH WILL LIFT NE WITH BEST FORCING/MOISTURE/INSTABILITY LIFTING N AND E...BRINGING AN END TO THE WIDESPREAD SHRA/TSRA AND SVR THREAT. THERE IS A MODERATE RISK FOR THE DEVELOPMENT OF RIP CURRENTS ALONG THE ATLANTIC OCEAN FACING BEACHES INTO THIS EVENING. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
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SURFACE LOW TRACKS THROUGH NEW ENGLAND ON MONDAY...WITH PRE-FRONTAL TROUGH MOVING NORTH AND RELATIVELY DRIER AIRMASS ADVECTING IN. BREEZY AND SEASONABLY WARM CONDITIONS ARE EXPECTED. CONSIDERABLE INSTABILITY CLOUD COVER AND DIURNAL SCT-NUM SHRA DEVELOPMENT LIKELY IN THE AFTERNOON WITH COLD POOL INSTABILITY AND DIURNAL HEATING...AS WELL AS ALONG AHEAD OF COLD FRONTAL PASSAGE IN AFT/EVE. GREATEST COVERAGE EXPECTED ACROSS THE INTERIOR OFF HIGHER TERRAIN. A FEW STRONG TO SEVERE STORMS ARE POSSIBLE...WITH HAZARDS IN THE FORM OF LARGE HAIL AND GUSTY WINDS. FRONT SHOULD CLEAR THE AREA MON EVE WITH DRIER AND COOLER AIRMASS ADVECTING IN. THERE IS A MODERATE RISK FOR THE DEVELOPMENT OF RIP CURRENTS ALONG THE ATLANTIC OCEAN FACING BEACHES DURING THE DAY MONDAY.
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&& .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... LINGERING CHC FOR PCPN OVER SOUTHERN CT/LOWER HUDSON RIVER VALLEY FIRST HALF OF MON NIGHT AS SFC LOW LIFTS TO THE NORTH...DRAGGING ITS ASSOCIATED COLD FRONT THROUGH THE EASTERN HALF OF THE AREA. 12Z MODEL GUIDANCE GENERALLY AGREEING THE BEST FORCING ALOFT ASSOCIATED WITH A PASSING VORT MAX SHOULD REMAIN NORTH AND EAST OF THE AREA...BUT MAY PUSH JUST SOUTH ENOUGH TO ASSIST IN PROLONGING ANY PCPN THAT DEVELOPED LATE IN THE DAY. BOTH INSTABILITY AND SHEAR ON THE WEAKER SIDE BY 00Z TUES...SO LOOKING FOR MORE ISO-SCT SHOWERS WITH A LOW END CHC OF A TSTM. BY 06Z...PCPN SHOULD HAVE CLEARED THE AREA WITH ANY FORCING AT BOTH THE SFC AND ALOFT NOW EXITING THE AREA. PW VALUES WILL ALSO HAVE DROPPED BEHIND THE FRONT...SO ANY FLOODING THREAT WITH THE SHOWERS WILL HAVE DIMINISHED. UPPER LEVEL TROUGH DIGS SOUTH TUES THROUGH MID WEEK WITH A CLOSED LOW HOVERING JUST NORTH OF THE GREAT LAKES. WITH MINIMAL PROGRESSIVE MOVEMENT ALOFT...THE COLD FRONT IS EXPECTED TO PUSH EAST...BUT THEN STALL OFFSHORE. IT SHOULD PUSH JUST FAR ENOUGH EAST TO HAVE MINIMAL IMPACT THROUGH THE COMING WEEK...BUT WILL COME BACK INTO THE PICTURE FOR THE COMING WEEKEND. AS THE SURFACE HIGH PRESSURE WILL BE BUILDING IN BEHIND THE FRONT AND WILL MAINTAIN HOLD OF THE REGION THROUGH THURS. SHORTWAVE ROTATING ON THE SOUTHERN EDGE OF THE TROUGH COULD TRIGGER AN ISO SHOWER/TSTM TUES AFTN OVER FAR NORTH AND WESTERN EDGES OF THE AREA...BUT WITH A MUCH DRIER AIRMASS MOVING IN...COULD VERY WELL END UP BEING A DRY DAY. THE NEXT MENTION OF PCPN COMES THURS AFTN WITH A RETURN FLOW SETTING UP OVER THE REGION...INJECTING IN A SLIGHTLY MORE MOIST AIRMASS. THE CLOSED LOW ALOFT FINALLY PUSHES OFF TO THE NORTHEAST...THOUGH A LONGWAVE TROUGH STILL WILL PERSIST OVER THE EASTERN HALF OF THE US FOR THE END OF THE WEEK. THE PATTERN STILL BRINGS THROUGH MULTIPLE SHORTWAVES THURS-FRI...EACH BRINGING A SLIGHT CHC IN TRIGGERING AN ISO SHOWER OR TSTM. LOW PRESSURE FORMS ALONG THE STALLED FRONT BY THIS WEEKEND...RIDING THE FRONT WHILE SLOWLY APPROACHING THE AREA. GENERAL MODEL CONSENSUS BRINGS THE SFC LOW NEAR THE TRI STATE AREA BY SUN MORNING. ENOUGH FORCING ALOFT ROUNDING THE BASE OF THE UPPER LEVEL TROUGH SHOULD COMBINE WITH THE SFC LOW TO PRODUCE SCT SHOWERS AND TSTMS...ESP FOR LATER SAT THROUGH SUN. TEMPS REMAIN NEAR STEADY THROUGH THE COMING WEEK...A FEW DEGREES BELOW NORMAL. && .AVIATION /21Z SUNDAY THROUGH FRIDAY/... PRE-FRONTAL SURFACE TROUGH WILL REMAIN IN THE VICINITY INTO THIS EVENING. ANOTHER PRE-FRONTAL TROUGH APPROACHES LATE TONIGHT AND EXITS TO THE EAST MONDAY MORNING. VFR INTO THIS EVENING. ISO/SCT SHRA/TSTM POSSIBLE AT ANY GIVEN TIME...BUT COVERAGE AND PROBABILITY ARE TOO LOW TO MENTION IN TAFS UNTIL SHORTLY AFTER MIDNIGHT TONIGHT WHEN STORMS BECOME MORE NUMEROUS. ANY STORM COULD PRODUCE STRONG GUSTY WINDS AND HAIL. SOUTHERLY WINDS 10 TO 15 KTS CAN BE EXPECTED INTO THIS EVENING. OCCASIONAL GUSTS 17-20 KT THIS AFTN. .OUTLOOK FOR 18Z MON THROUGH FRI... .MON PM...MAINLY VFR. CHC SHRA/TSTMS. CHC TEMPO SUB-VFR. .TUE-THUR...VFR. .FRI...MOSTLY VFR. ISO SHRA/TSTM && .MARINE... MODERATE SOUTHERLY WINDS CONTINUE OVERNIGHT AHEAD OF LOW PRESSURE AND ASSOCIATED COLD FRONT. MARGINAL SCA WILL BUILD SLIGHTLY AND REMAIN IN THE 4 TO 7 FT RANGE TONIGHT INTO MONDAY. MARGINAL SCA GUSTS EXPECTED MONDAY AFTERNOON ACROSS ALL NEARSHORE WATERS IN WAKE OF FRONT. SEAS ON THE OCEAN ARE EXPECTED TO REMAIN ELEVATED...5-7 FT MON NIGHT THROUGH TUES MORNING. AS THE WINDS SHIFT AROUND TO THE NW...SEAS WILL BEGIN TO SUBSIDE...WITH SUB-SCA CONDITIONS EXPECTED BY TUES AFTN. SUB-SCA CONDITIONS ON ALL WATERS THEN THROUGH THE REMAINDER OF THE WEEK...WITH A POSSIBLE RETURN TO 25 KT GUSTS AND 5 FT SEAS OVER THE WEEKEND DEPENDING ON THE TRACK OF THE LOW. && .HYDROLOGY... SCATTERED TO NUMEROUS SHOWERS/TSTMS ARE FORECAST TONIGHT INTO EARLY MONDAY MORNING WITH AN APPROACHING FRONTAL SYSTEM. ANY OF THESE STORMS HAVE THE POTENTIAL TO PRODUCE HEAVY DOWNPOURS. SOME UNCERTAINTY STILL EXISTS WITH COVERAGE OF THUNDERSTORMS THOUGH. MINOR URBAN FLOODING IS POSSIBLE WITH THESE HEAVY DOWNPOURS...BUT FLASH FLOODING IS NOT EXPECTED SINCE STORMS SHOULD BE MOVING AND TRAINING IS NOT ANTICIPATED. SCATTERED CONVECTION IS LIKELY MONDAY AFTERNOON...WITH LOCALIZED MINOR URBAN FLOOD THREAT. NO SIGNIFICANT HYDROLOGIC ISSUES ARE EXPECTED TUES THROUGH THE END OF THE WEEK. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY FROM 11 AM TO 6 PM EDT MONDAY FOR ANZ330- 335-338-340-345. SMALL CRAFT ADVISORY UNTIL 6 PM EDT MONDAY FOR ANZ350-353-355. && $$ SYNOPSIS...SEARS/NV NEAR TERM...NV SHORT TERM...NV LONG TERM...SEARS AVIATION...JC MARINE...SEARS/NV HYDROLOGY...SEARS/NV

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