Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 270528 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 128 AM EDT SUN JUL 27 2014 .SYNOPSIS... A WARM FRONT APPROACHES FROM THE SOUTHWEST TONIGHT...LIFTING THROUGH THE AREA SUNDAY WITH A COLD FRONT APPROACHING SUNDAY NIGHT. A COLD FRONT PUSHES THROUGH THE AREA ON MONDAY...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 /UNTIL 11 AM THIS MORNING/...
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NEXT WAVE WAS PRODUCING SHOWERS ACROSS WESTERN PENNSYLVANIA AND INTO CENTRAL MARYLAND. THE ACTIVITY WAS SLIDING TO THE SOUTHEAST. MAY SEE ADDITIONAL SHOWERS DEVELOP AND APPROACH THE AREA EARLY THIS MORNING. THE WAVE WILL PRODUCE A SURFACE WAVE THAT WILL TRACK EAST THROUGH ONTARIO...WITH ACCOMPANYING WARM FRONT APPROACHING THE REGION TOWARDS DAYBREAK. INCREASING THETA-E/INSTABILITY WITH A DEVELOPING LLJ AHEAD OF THE WARM FRONT AND MID/UPPER FORCING WILL INCREASE THE CHANCE FOR SHOWERS AND THUNDERSTORMS W TO E LATE TONIGHT INTO SUN MORNING FROM THE NYC METRO AND PTS WEST...AND SUN MORNING INTO EARLY AFTERNOON FOR LI/CT. MODELS ARE IN GOOD AGREEMENT WITH STRONG DEEP LAYER SHEAR AND AT LEAST MODERATE LOW-LEVEL SHEAR FIELDS ALONG/AHEAD OF WARM FRONT LATE TONIGHT INTO SUNDAY MORNING. THE INSTABILITY ENVIRONMENT IS A BIT IN QUESTION THOUGH FOR LATE TONIGHT INTO SUNDAY MORNING...AS MODELS ARE HANDLING ADVECTION OF STEEP MID-LEVEL LAPSE RATES FROM MID-MISSISSIPPI RIVER VALLEY A BIT DIFFERENTLY. BUT IF STEEP LAPSE RATES ARE MAINTAINED...AN ELEVATED MODERATELY UNSTABLE ENVIRONMENT WOULD BE REALIZED...WHICH WOULD BE FAVORABLE FOR SOME STRONG TO SEVERE CONVECTION IF LOW-LEVEL INVERSION CAN BE OVERCOME. MODERATE INSTABILITY WITH STRONG SHEAR LEVELS WOULD INCLUDE POTENTIAL FOR ORGANIZED STORMS AND POTENTIALLY ROTATING. WILL ADDRESS THIS IN HWO.
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&& .SHORT TERM /11 AM THIS MORNING THROUGH 6 PM MONDAY/... SHORTWAVE AND WARM FRONT SHOULD PUSH NE OF THE REGION SUNDAY AFTERNOON WITH ASSOCIATED EARLY CONVECTION EXPECTED TO BE PUSHING EAST. ACROSS THE NYC METRO AND POINTS WEST...POTENTIAL EXISTS FOR PARTIAL CLEARING WHICH SHOULD ALLOW TEMPS TO RISE WELL INTO 80S...TO AROUND 90 DEGREES NYC/NJ METRO. A SIGNIFICANT INCREASE IN HUMIDITY LEVEL WILL BE FELT IN THE WAKE OF THE WARM FRONT. IN TERMS OF CONVECTION POTENTIAL SUNDAY AFTERNOON...MODERATE INSTABILITY LEVELS ARE LIKELY FROM NYC METRO AND POINTS WEST...WITH POTENTIAL FOR POCKETS OF HIGH INSTABILITY ACROSS NE NJ/LOWER HUDSON VALLEY DEPENDING, THIS WILL DEPEND OF THE PERSISTENCE OF THE STEEPER MID-LEVEL LAPSE RATES AND WITH ANY BREAKS OF SUN. THE QUESTION APPEARS TO BE TRIGGER IN AFT...AS REGION COULD BE IN SOME WEAK SUBSIDENCE IN WAKE OF THE MORNING/EARLY AFT SHORTWAVE. AT THE SURFACE...A THERMAL TROUGH IS LIKELY IN THE VICINITY OF NJ/LOWER HUDSON VALLEY WHICH COULD BE A FOCUS. INTERESTINGLY...THE NAM HOLDS THE WARM FRONT ACROSS THE REGION DURING THE DAY...WHICH WOULD BE A FOCUS FOR ROTATING STORMS AND TRAINING THUNDERSTORMS/FLASH FLOODING. THIS IS A LOW PROB SOLUTION. FOR NOW...WILL HANDLE WITH GRADUALLY INCREASING CHANCE POPS IN THE AFTERNOON INTO THE EVENING FROM NYC AND POINTS N&W AS POTENTIAL FOR APPROACHING SHORTWAVE/JET ENERGY INCREASES. IF CONVECTION IS TRIGGERED...POTENTIAL IS THERE FOR ORGANIZED LINE SEGMENTS TO SEVERE LEVELS BASED ON INSTABILITY...AND MODEST UNIDIRECTIONAL SHEAR LEVELS. MODELS IN GOOD AGREEMENT WITH LEAD SHORTWAVE ENERGY SWINGING THROUGH THE REGION MON NIGHT...AHEAD OF A WEAKENING APPROACHING UPPER LOW APPROACHES. AT THE SURFACE...ASSOCIATED LOW PRESSURE TRACKS THROUGH THE EASTERN GREAT LAKES INTO CENTRAL NY SUN NIGHT...WITH A STRONG COLD FRONT APPROACHING THE REGION. UNCERTAINTY STILL EXISTS IN TERMS OF CONVECTIVE COVERAGE WITH THIS FEATURE OVERNIGHT. MOST WIDESPREAD ACTIVITY WOULD BE WITH SURFACE LOW AND WARM FRONT ACROSS CENTRAL NY/NEW ENGLAND. ALSO...SOME OF THE MODEL GUIDANCE INDICATES A SECONDARY LOW/TRIPLE POINT...POSSIBLY MCS RELATED...WORKING THROUGH MID-ATLANTIC INTO SOUTHERN NJ SUN NIGHT. TO THE SOUTH OF THE AREA WOULD BE THE MOST FAVORABLE MCS TRACK BASED ON WIND FIELDS/THETA-E GRADIENT. THE PRESENCE OF THIS TYPE OF FEATURE OVER OUR AREAS WOULD BRING POTENTIAL FOR ROTATING STORMS AND FLASH FLOODING INTO THE OVERNIGHT. CURRENTLY THAT LOOKS TO BE A LOW POTENTIAL. WITH ALL THAT SAID...THE REGION COULD END UP BEING IN THE MIDDLE OF FAVORABLE REGIONS. BUT WITH STRONG FORCING/SHEAR...INCLUDING AN UNSEASONABLY STRONG LLJ...AND STRONG COLD FRONT INTERACTING WITH A MARGINAL TO MODERATELY UNSTABLE ENVIRONMENT WOULD EXPECT ANY STRONG TO SEVERE LATE DAY/EVE CONVECTION TO ONLY SLOWLY LOOSE INTENSITY AS IT WORKS EASTWARD. SO WILL CONTINUE WITH LIKELY POPS FOR SHRA AND SCATTERED STRONG TSTMS OVERNIGHT...TAPERING FROM W TO E LATE SUN NIGHT. THERE IS A MODERATE RISK FOR THE DEVELOPMENT OF RIP CURRENTS ALONG THE ATLANTIC OCEAN FACING BEACHES DURING THE DAY SUNDAY. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... UPPER LVL CLOSED LOW POSITIONED OVER SOUTHERN CANADA DIGS TO THE SOUTH MONDAY AND WILL REMAIN POSITIONED OVER THE NORTHEAST THROUGH MOST OF THE COMING WEEK. MEANWHILE...12Z MODEL SUITE CONTINUING WITH THE DEVELOPMENT OF A SECONDARY LOW OVER THE EASTERN GREAT LAKES SUNDAY NIGHT...WITH THE MOVEMENT OF THE LOW PUSHING IT THROUGH NEW ENGLAND MONDAY. AS THE LOW LIFTS NORTH OF THE AREA...ITS ASSOCIATED COLD FRONT WILL BE DRAGGED THROUGH. THE FRONT SHOULD CLEAR THE EASTERN AREAS BY MON NIGHT...BUT STALLING TO THE EAST WITH LITTLE MOVEMENT ALOFT ALLOWING IT TO PROGRESS FURTHER EAST TILL WED. EVENTUALLY HIGH PRESSURE WILL BEGIN TO BUILD IN WED 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 /06Z SUNDAY THROUGH THURSDAY/...
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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.
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&& .MARINE... WIND AND SEAS REMAIN ON TRACK...EXPECTING SUB SCA CONDS TONIGHT. INCREASING WINDS SUNDAY AND SUNDAY NIGHT OUT AHEAD OF LOW PRESSURE AND ASSOCIATED COLD FRONT WILL HELP SEAS BUILD TO MARGINAL SCA AS A RESULT LATE SUNDAY INTO SUNDAY NIGHT AND REMAIN RATHER ROUGH MONDAY. AN APPROACHING COLD FRONT MONDAY COULD INCREASE GUSTS TO AROUND 25 KTS...ESP ON THE OCEAN WATERS. BUILDING SEAS FROM A PERSISTENT SLY FLOW OVER THE WEEKEND WILL REACH BETWEEN 4-6 FT ON THE OCEAN DURING THE DAY MONDAY AS WELL. IN THE WAKE OF THE FRONT BEGINNING MON NIGHT...EXPECTING SUBSIDING SEAS AND WEAKENING WINDS. ALL WATERS SHOULD RETURN TO SUB-SCA CONDITIONS BY TUES AFTN. HIGH PRESSURE BUILDING OVER THE WATERS WILL AID IN KEEPING SUB-SCA CONDITIONS THEN THROUGH THE END OF THE 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. SIGNIFICANT UNCERTAINTY STILL EXISTS WITH TIMING AND COVERAGE OF THUNDERSTORMS THOUGH. IT LOOKS LIKE THE HIGHER POTENTIAL FOR HEAVY RAIN IS SUNDAY AFTN AND SUNDAY NIGHT WITH HIGHER PWATS OF 1.5 TO 2 INCHES ACROSS THE REGION. NO SIGNIFICANT RAINFALL EXPECTED FOR THE REMAINDER OF THE WEEK.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM EDT MONDAY FOR ANZ350-353-355.
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&& $$

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