Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 271449 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1049 AM EDT SUN JUL 27 2014 .SYNOPSIS... A WARM FRONT APPROACHING FROM THE SOUTHWEST WILL LIFT THROUGH THE AREA LATER TODAY. AS A COLD FRONT APPROACHES TONIGHT...A STRENGTHENING AREA OF LOW PRESSURE WILL TRACK FROM THE EASTERN GREAT LAKES TO SOUTHERN NEW ENGLAND BY MORNING. THE LOW WILL TRACK THROUGH NEW ENGLAND ON MONDAY AS THE COLD FRONT MOVES ACROSS THE LOCAL AREA...REMAINING JUST TO THE EAST THROUGH TUESDAY. HIGH PRESSURE BUILDS IN FOR THE SECOND HALF OF THE WEEK BEFORE THE NEXT LOW PRESSURE SYSTEM APPROACHES NEXT WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... INITIAL CONCERN FOR LATE THIS MORNING THOUGH EARLY AFTERNOON IS SHORTWAVE APPROACHING FROM CENTRAL NY AND WARM FRONT LIFTING THROUGH THE REGION FROM SW TO NE. CURRENTLY MORE WIDESPREAD AREAS OF CONVECTION ARE TO THE NORTH AND SOUTH OF THE REGION...BUT WITH THE SHORTWAVE/FRONT INTERACTING WITH A MARGINAL TO MODERATELY UNSTABLE ENVIRONMENT AND IN A MODERATE TO STRONG DEEP LAYER SHEAR ENVIRONMENT...POTENTIAL EXISTS FOR SCATTERED SHOWERS AND THUNDERSTORMS THIS MORNING THROUGH EARLY AFTERNOON...A FEW OF WHICH COULD BE STRONG TO POSSIBLE SEVERE. CAN NOT RULE OUT EVEN SOME ROTATION WITH THEM STORMS IN VICINITY OF WARM FRONT WITH SUFFICIENT LOW-LEVEL SHEAR/HELICITY. ONCE THE FRONT LIFTS THROUGH THE AREA...EXPECT PARTIAL CLEARING AND AT LEAST MODERATE DESTABILIZATION. CONVECTIVE COVERAGE DURING THE MID AFTERNOON INTO EARLY EVENING IS A BIT UNCERTAIN IN THE WAKE OF THE INITIAL SHORTWAVE ENERGY AND LIKELY WEAK SUBSIDENCE AND EVEN A BIT OF MID-LEVEL CAPPING. COVERAGE SHOULD BE WIDELY SCATTERED/ISOLATED DURING THIS TIME...MORE LIKELY OFF HIGHER TERRAIN AND DRIFTING WEST. ANYTHING THAT DOES DEVELOPS HAS POTENTIAL TO BE STRONG TO SEVERE...WITH SHEAR/INSTABILITY LEVELS SUPPORTIVE. POTENT SHORTWAVE AND STRENGTHENING SFC LOW APPROACHES TONIGHT...WITH ANOTHER ROUND OF SHRA/TSTMS EXPECTED AND POTENTIAL FOR A GREATER COVERAGE SVR WEATHER EVENT. 0-6KM SHEAR WILL AGAIN BE MODERATE...APPROACHING STRONG LEVELS WITH 0-1KM SHEAR BETWEEN 15-20 KTS AND INCREASING HELICITY BETWEEN 00Z AND 06Z. THERE IS SOME SLIGHT TIMING DIFFERENCES BETWEEN THE GUIDANCE...BUT ENVIRONMENT LOOKS FAVORABLE FOR ROTATING STORMS. SPC HAS PLACED THE ENTIRE AREA IN A SLIGHT RISK...WITH A 5 PERCENT CHANCE FOR TORNADOES IN NYC AND WESTERN LONG ISLAND AND A 2 PERCENT CHC ELSEWHERE. OTHERWISE...DAMAGING WINDS AND LARGE HAIL HAVE ABOUT THE SAME CHANCE OF OCCURRING...OUTSIDE OF THE AFOREMENTIONED AREAS WHERE THERE IS A 30 PERCENT CHANCE OF THUNDERSTORM WIND DAMAGE...WITH WET BULB ZERO HEIGHTS NEAR OR SLIGHTLY BELOW 10K FT. AS THE LOW TRACKS INTO SOUTHERN NEW ENGLAND LATE TONIGHT INTO MONDAY MORNING...THE BEST DYNAMICAL FORCING WILL LIFT N AND E BRINGING AN END TO THE SVR THREAT. THE TIMING WILL NEED TO BE REFINED AS THINGS UNFOLD. THERE IS A MODERATE RISK FOR THE DEVELOPMENT OF RIP CURRENTS ALONG THE ATLANTIC OCEAN FACING BEACHES THROUGH THIS EVENING. && .SHORT TERM /MONDAY THROUGH TUESDAY/... LOW TRACKS THROUGH NEW ENGLAND ON MONDAY AS ITS ATTENDING COLD FRONT MOVES ACROSS THE AREA. POTENTIAL FOR SCT CONVECTION DURING THE AFTN...WITH A FEW STRONG STORMS MAINLY E OF NYC...BUT WILL DEPEND ON FRONTAL PROGRESSION. HIGHS ARE ALSO TROUBLESOME DUE TO THIS. FRONT SHOULD CLEAR THE AREA MON EVE AND REMAIN JUST E OF THE AREA THROUGH TUE. A MORE COMFORTABLE AIRMASS WILL FOLLOW IN THE WAKE OF THE FRONT. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... HIGH PRESSURE WILL BEGIN TO BUILD IN TUE NIGHT AND SHOULD TAKE HOLD OF THE AREA THROUGH THE END OF THE WEEK. MODEL DISCREPANCIES IN THE HANDLING OF THE NEXT LOW PRESSURE SYSTEM BUT SOME FORM OF LOW PRESSURE WILL BEGIN TO APPROACH BY NEXT WEEKEND...THOUGH COULD HOLD OFF ANY IMPACTFUL WEATHER TILL THE WORK WEEK. CONCERNING THE PCPN FOR MONDAY...WILL BE WATCHING THE PATH THE LOW TAKES AS IT FORMS SUNDAY NIGHT. RIGHT NOW THE AREA WILL REMAIN POSITIONED BETWEEN A WARM FRONT TO THE NORTH AND THE COLD FRONT TO THE WEST. AS SUCH...EXPECTING DECENT INSTABILITY AND SHEAR IN PLACE TO ALLOW FOR TSTM DEVELOPMENT. QUESTION REMAINS THOUGH OF WHERE/WHEN THE SHORTWAVES PIVOT AROUND THE UPPER LVL TROUGH. MODELS AGREE ON STRONG VORT MAX OVER NE PA BY 18Z MON THEN LIFTING ON INTO NEW ENGLAND...JUST SKIRTING THE NORTHERN FRINGES OF THE AREA. WHILE THERE WONT BE A LACK OF FORCING ALOFT OVER THE REMAINDER OF THE AREA...IT WILL BE ON THE WEAKER END. SO WITH THIS THINKING...MAINTAINED CHC POPS BASICALLY NYC METRO AND TO THE EAST AND SOUTH...WHILE INCLUDING LIKELY POPS TO THE NORTH AND WEST WITH NOW CONSECUTIVE MODEL RUNS HINTING AT THE SECONDARY LOW FORMATION. STRONGER STORMS ARE NOT OUT OF THE QUESTION...THINKING MORE TO THE NORTH AND EAST OVER PORTIONS OF CT WITH THE BETTER FORCING AND THE ASSISTANCE OF THE COLD FRONT AT THE SFC. PCPN WILL CLEAR THE AREA MON NIGHT ON INTO TUES MORNING. ANOTHER SHORTWAVE PIVOTING THE TROUGH COULD BRING SLIGHT CHC OF TSTMS TUES AFTN. DESPITE MULTIPLE WEAKER SHORTWAVES PROGRESSING THROUGH MID WEEK...EXPECTING A MUCH DRIER AIRMASS IN PLACE AS THE HIGH BUILDS IN WITH NOTHING TO ASSIST IN TRIGGERING ANY CONVECTION. THE QUESTION THEN TURNS TO THE PCPN CHCS FOR THE COMING WEEKEND. WITH SUCH A SPREAD IN THE GLOBAL MODEL SOLUTIONS...WILL MAINTAIN SLIGHT CHC WORDING FOR NOW. OTHER THAN MONDAY...EXPECTING TEMPS A FEW DEGREES BELOW NORMAL FOR THE COMING WEEK WITH THE PERSISTENT NW-N FLOW. && .AVIATION /13Z SUNDAY THROUGH THURSDAY/... WARM FRONT MOVES NORTHWARD TODAY AS A COLD FRONT APPROACHES TONIGHT. SHRA WILL BE POSSIBLE AT ANY GIVEN TIME...BUT MAINLY VFR WITH TEMPO MVFR UNTIL EARLY AFTN. POSSIBLE BRIEF MVFR CONDS POSSIBLE LATER THIS AFTN INTO THIS EVENING WITH IS0/SCT SHRA/TSRA. ANY STORM COULD PRODUCE STRONG GUSTY WINDS AND HAIL. SOUTH WINDS 10 TO 15 KTS CAN BE EXPECTED THROUGH TODAY AND INTO TONIGHT. GUSTS MIGHT BE ONLY OCCASIONAL. .OUTLOOK FOR 12Z MON THROUGH THU... .MON...MAINLY VFR. CHC SHRA/TSTMS. CHC TEMPO SUB-VFR. .TUE-THU...VFR. && .MARINE... SOUTHERLY WINDS INCREASE TODAY AND TONIGHT AHEAD OF LOW PRESSURE AND ASSOCIATED COLD FRONT. OCEAN SEAS BUILD TO MARGINAL SCA AS A RESULT BY LATE TODAY AND THROUGH TONIGHT. SEAS REMAIN RATHER ROUGH MONDAY. THE APPROACHING COLD FRONT MONDAY COULD INCREASE GUSTS TO AROUND 25 KTS...ESPECIALLY ON THE OCEAN WATERS. THEN WINDS TURN TO THE WEST LATE IN THE DAY...WITH A FEW GUSTS OF 25 TO 30 KTS POSSIBLE BEHIND THE FRONT FOR A SHORT TIME. WINDS DIMINISH QUICKLY MONDAY NIGHT...ALLOWING SEAS TO SUBSIDE BY TUESDAY. HIGH PRESSURE BUILDS OVER THE WATERS MID TO LATE WEEK. && .HYDROLOGY... UNSETTLED WEATHER WITH SCATTERED TO NUMEROUS SHOWERS/TSTMS ARE FORECAST THROUGH MONDAY. ANY OF THESE STORMS HAVE THE POTENTIAL TO PRODUCE HEAVY DOWNPOURS. SOME UNCERTAINTY STILL EXISTS WITH TIMING AND COVERAGE OF THUNDERSTORMS THOUGH. IT LOOKS LIKE THE HIGHER POTENTIAL FOR HEAVY RAIN IS LATE THIS AFTN AND TONIGHT WITH HIGHER PWATS OF 1.5 TO 2 INCHES ACROSS THE REGION. 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. NO SIGNIFICANT RAINFALL THEN EXPECTED FOR THE REMAINDER OF THE WEEK. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 6 PM EDT MONDAY FOR ANZ350-353-355. && $$

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