Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 270839 CCA AFDOKX AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE NEW YORK NY 438 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/... AT 07Z...WARM FRONT APPEARED TO BE ORIENTED FROM JUST N OF KWAL...KDCA...KUNV...KBUF. IT WILL CONTINUE TO LIFT NWD PASSING THROUGH THE LOCAL AREA LATER TODAY. THETA-E ADVECTION ACROSS THE AREA THIS MORNING WILL INCREASE MOISTURE AND INSTABILITY AS THE LEFT EXIT REGION OF AN 80KT H25 JET APPROACHES. THIS IS EXPECTED TO TRIGGER SHRA/TSTM ACTIVITY ACROSS EASTERN PA/WESTERN NJ AND CONTINUE THROUGH THE MORNING AS IT TRACKS EWD. INSTABILITY IS WEAK THIS MORNING...BUT SHEAR IS MODERATE AND BEING IN THE LEFT EXIT REGION OF THE UPPER JET COULD RESULT IN A FEW STRONG STORMS...ESPECIALLY AFTER 12Z. WITH THE WARM FRONT NEARBY...CAN`T RULE OUT A FEW ROTATING STORMS WITH A VEERING LOW LEVEL WIND PROFILE...AND LCL`S AROUND 1K FT E OF NYC. HI RES MODELS ARE IN DECENT AGREEMENT IN INCREASING ACTIVITY THIS MORNING...WHICH COULD IMPACT WHAT HAPPENS LATER TODAY. ONCE THE FRONT LIFTS THROUGH THE AREA LATER TODAY...THERE COULD BE SEVERAL HOURS OF DRY WEATHER BEFORE THE NEXT SHORTWAVE IMPACTS THE AREA. EXPECT PARTIAL CLEARING FOR A FEW HOURS WHICH THIS WILL DETERMINE THE AMOUNT OF DESTABILIZATION THAT OCCURS AS THE POTENT SHORTWAVE AND STRENGTHENING SFC LOW APPROACHES FOR THE EVENING. ANOTHER ROUND OF SHRA/TSTMS IS EXPECTED WITH THIS FEATURE...WITH THE POTENTIAL FOR A MORE SIGNIFICANT 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 THIS APPEARS TO BE THE BETTER CHANCE 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 TONIGHT...THE BEST DYNAMICAL FORCING WILL LIFT N AND E BRINGING AN END TO THE SVR THREAT. THE TIMING WILL NEED TO BE REFINED LATER TODAY AS THINGS UNFOLD...BUT EXPECT ACTIVITY TO LINGER THROUGH MUCH IF NOT ALL OF THE NIGHT...ESPECIALLY EASTERN AREAS. 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 /08Z SUNDAY THROUGH THURSDAY/... A TROUGH AND WARM FRONT MOVE TOWARD THE AREA FROM THE SOUTHWEST THIS MORNING. DURING THE AFTERNOON THE WARM FRONT IS EXPECTED TO PASS TO THE NORTH. PATCHY STRATUS EARLY THIS MORNING COULD RESULT IN SUB VFR CONDITIONS BRIEFLY. AFTER SUNRISE...POSSIBLE SHOWERS AND THUNDERSTORMS DEVELOP WITH MARGINAL VFR CONDITIONS AND ALSO IFR IN HEAVIER STORMS ALONG WITH GUSTY WIND AND SMALL HAIL. AFTER THIS ACTIVITY MOVES EAST... THERE WILL BE CLEARING WITH ANOTHER ROUND OF STORMS TOWARD THE END OF THE FORECAST PERIOD...00Z...AND INTO THE EVENING HOURS. .OUTLOOK FOR 06Z MON THROUGH THU... .TONIGHT...SHRA AND SCT TSTMS. CHC TEMPO MVFR TO IFR. .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...
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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.
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&& .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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