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/...
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.

&&

.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/...
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...
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...
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.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
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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