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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KOKX 212357
AFDOKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
757 PM EDT TUE MAY 21 2013

.SYNOPSIS...
A FRONTAL BOUNDARY WILL REMAIN JUST NORTH OF THE REGION THROUGH
WEDNESDAY AS A COLD FRONT SLOWLY APPROACHES FROM THE WEST. THE
COLD FRONT WILL PASS THROUGH THE AREA LATE THURSDAY NIGHT INTO
FRIDAY MORNING. CANADIAN HIGH PRESSURE BUILDS IN FOR THE WEEKEND
AND EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
ADVECTION FOG/STRATUS REMAINS ALONG THE SOUTH SHORE OF EASTERN SUFFOLK
COUNTY. DENSE FOG ADVISORY THERE THROUGH 10 AM WED...THOUGH THIS
WILL LIKELY NEED EXPANDING AS THE NIGHT PROGRESSES. CONFIDENCE ON
THIS THOUGH IS NOT THAT HIGH AT THIS TIME TO WARRANT EXPANSION.

LATE THIS AFTERNOON...WITH TEMPS NEAR 90 AND ABUNDANT MOISTURE...
INSTABILITY IS MAXIMIZED. THE LACK OF A TRIGGER AWAY FROM THE
FRONT HAS KEPT CONVECTION LIMITED. HAVE LOWERED POPS FOR THIS
EVENING AND KEPT IT CONFINED TO THE INTERIOR AS A RESULT. EVEN
THESE POPS MAY BE OVER DONE. WITH THE LACK OF MORE EXTENSIVE
CONVECTIVE INITIATION SO FAR...HAVE DROPPED MENTION OF CONVECTION
THIS EVENING IN THE HAZARDOUS WEATHER OUTLOOK.

WARM AND MUGGY OVERNIGHT WITH BLENDED MOS ACCEPTED.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
LOOKS LIKE A SIMILAR DAY ON WEDNESDAY AS RIDGE SLOWLY SHIFTS
EAST. MORNING FOG AND STRATUS WILL GIVE WAY TO AT LEAST PARTIAL
SUNSHINE. CONVECTION SHOULD BE SCATTERED AT BEST WITH ONLY MARGINAL
INSTABILITY IN PLACE...LESS THAN TODAY. HIGHS IN THE MID
80S...EXCEPT ALONG THE COAST.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
THE UPPER TROUGH OVER THE MID SECTION OF THE COUNTRY TRANSLATES
EAST THROUGH THE END OF THE WEEK AND THEN OFFSHORE BY THE WEEKEND.
INTERACTION WITH SHORT WAVE ENERGY IN THE NORTHERN BRANCH OF THE
POLAR JET ACROSS EASTERN CANADA WILL AMPLIFY THE TROUGH ACROSS THE
OH VALLEY AND MID ATLANTIC STATES. THIS AMPLIFICATION RESULTS IN
TIMING ISSUES AMONGST THE GLOBAL MODELS...WITH THE OPERATIONAL 12Z
GFS THE SLOWEST AT THE WESTERN END OF THE ENVELOPE. THE ECMWF AND
GGEM ARE THE QUICKEST WITH SWINGING THE FRONT ACROSS THE COAST BY
FRI MORNING. IN FACT...THE GFS CONTINUES TO BECOME MUCH SLOWER
THAN ALL THE GUIDANCE FRI INTO SAT AS THE UPPER LOW CLOSES OFF
APPROACHING THE MID ATLANTIC STATES...TAKING ON A NEGATIVE TILT
MUCH CLOSER TO THE COAST. THIS WOULD RESULT IN A PROLONGED PERIOD
OF POST-FRONTAL RAIN INTO SAT. PREFERENCE AT THIS TIME WAS TO LEAN
TOWARD THE FASTER MODEL CONSENSUS WITH PCPN SHUTTING DOWN FRI
AFT. SUBSEQUENT MODEL TRENDS WILL NEED TO BE CLOSELY MONITORED TO
SEE IF THE FRONTAL SYSTEM SLOWS DOWN EVEN FURTHER.

AS FOR THE SENSIBLE WEATHER...COLD FRONT APPROACHES FROM THE WEST
THU...PASSING ACROSS THE REGION THU NIGHT INTO FRI. HIGH PW
VALUES AND MODERATE INSTABILITY WILL LEAD TO THE DEVELOPMENT OF
WIDESPREAD SHOWERS AND THUNDERSTORMS THAT WORK WEST TO EAST
DURING THIS TIME. THE ISOLATED SEVERE THREAT APPEARS LOW AT THIS
TIME WITH THE LOW-LEVEL JET DISPLACED EAST OF THE AREA AND
MARGINAL DEEP LAYER SHEAR. UNIDIRECTIONAL WIND PROFILES SUPPORT
SOME BOWING LINE SEGMENTS WITH GUSTY WINDS. WET-BULB ZERO VALUES ARE
WARM...SUPPORTING ONLY SMALL HAIL. THE MAIN THREAT LOOKS TO BE
THE POTENTIAL FOR HEAVY RAINFALL...ESPECIALLY IF THE UPPER FLOW
BACKS FURTHER WITH THE AMPLIFICATION OF THE UPPER TROF TO THE
WEST. AVERAGE BASIN RAINFALL SHOULD BE CLOSE TO AN INCH...WITH
LOCALIZED HIGHER AMOUNTS.

A DRIER NW FLOW SET UPS FRI NIGHT WITH STRONG COLD ADVECTION. HIGH
PRESSURE BUILDS ACROSS THE GREAT LAKES AND INTO THE MID ATLANTIC
STATES THROUGH EARLY NEXT WEEK WITH TEMPERATURES SEVERAL DEGREES
BELOW SEASONABLE LEVELS.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
A NEARLY STATIONARY FRONT WILL REMAIN NORTH OF THE TERMINALS THROUGH
WEDNESDAY AFTERNOON.

STRATUS AND FOG IS EXPECTED TO DEVELOP THIS EVENING AFTER 03Z WITH
CEILINGS AND VISIBILITIES BECOMING IFR AND AS LOW AS VLIFR AT THE
COASTAL TERMINALS ESPECIALLY AFTER 07Z. CONDITIONS IMPROVE EARLY
WEDNESDAY MORNING...13Z TO 15Z. TIMING OF IMPROVEMENT AND CONDITIONS
UNCERTAIN. WIND WILL BE LIGHT FROM THE SOUTH THROUGH THE NIGHT THEN
INCREASE TO 10 TO 15 KT DURING WEDNESDAY.

SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE AFTER 16Z MAINLY NORTH
AND WEST OF THE NEW YORK TERMINALS.


     NY METRO ENHANCED AVIATION WEATHER SUPPORT...

DETAILED INFORMATION...INCLUDING HOURLY TAF WIND COMPONENT FCSTS
CAN BE FOUND AT:  HTTP:/WWW.ERH.NOAA.GOV/ZNY/N90 (LOWER CASE)

KJFK FCSTER COMMENTS: FOG AND STRATUS DEVELOP AFTER 05Z...MAY BE AN
HOUR OR SO SOONER. CONDITIONS IMPROVE AFTER 13Z. SHOWERS AND
THUNDERSTORMS POSSIBLE AFTER 19Z.

KLGA FCSTER COMMENTS: FOG AND STRATUS DEVELOP AFTER 08Z...MAY BE AN
HOUR OR SO SOONER. CONDITIONS IMPROVE AFTER 13Z. SHOWERS AND
THUNDERSTORMS POSSIBLE AFTER 19Z.

KEWR FCSTER COMMENTS: FOG AND STRATUS DEVELOP AFTER 09Z...MAY BE AN
HOUR OR SO SOONER. CONDITIONS IMPROVE AFTER 13Z. SHOWERS AND
THUNDERSTORMS POSSIBLE AFTER 19Z.

KTEB FCSTER COMMENTS: FOG AND STRATUS DEVELOP AFTER 09Z...MAY BE AN
HOUR OR SO SOONER. CONDITIONS IMPROVE AFTER 13Z. SHOWERS AND
THUNDERSTORMS POSSIBLE AFTER 17Z.

KHPN FCSTER COMMENTS: FOG AND STRATUS DEVELOP AFTER 06Z...MAY BE AN
HOUR OR SO SOONER. CONDITIONS IMPROVE AFTER 13Z. SHOWERS AND
THUNDERSTORMS POSSIBLE AFTER 17Z.

KISP FCSTER COMMENTS: FOG AND STRATUS DEVELOP AFTER 03Z...MAY BE AN
HOUR OR SO SOONER. CONDITIONS IMPROVE AFTER 14Z.

.OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...
.WEDNESDAY NIGHT...SCT SHRA AND TSTMS POSSIBLE. IFR POSSIBLE IN FOG
AND STRATUS.
.THURSDAY-FRIDAY...NUMEROUS SHRA AND TSTMS POSSIBLE. IFR POSSIBLE IN
FOG AND STRATUS.
.SATURDAY...RESIDUAL SHRA BEHIND A COLD FRONT WITH MVFR. BECOMING VFR
WITH NW WINDS INCREASING TO 20-30KT.
.SUNDAY...VFR WITH NW WINDS 20-25KT.
-- End Changed Discussion --

&&

.MARINE...
DENSE FOG ACROSS THE EASTERN OCEAN WATERS...MAINLY NEAR SHORE...AND
THE EASTERN GREAT SOUTH BAY. THIS ADVECTION FOG IS EXPECTED TO
EXPAND BACK WEST OVERNIGHT.

SOUTH SOUTHWEST SUB SCA WINDS CONTINUE THROUGH WEDNESDAY NIGHT.
SEAS SHOULD SLOWLY BUILD WEDNESDAY...BUT HAVE UNDERCUT WAVEWATCH
TO PREVENT REACHING SCA CRITERIA UNTIL WEDNESDAY NIGHT. THINKING
WITH STRONG INVERSION THAT WIND FORCING WAS OVERDONE IN THE WW3
FORECAST.

A COLD FRONT WILL MOVE ACROSS THE AREA WATERS FRIDAY MORNING...WITH
HIGH PRESSURE BUILDING THROUGH THE WEEKEND. WINDS COULD BE BELOW
SCA LEVELS BY FRIDAY MORNING...WITH SEAS ON THE OCEAN REMAINING
ABOVE SCA CRITERIA THROUGH MUCH SATURDAY MORNING. UNDERCUT
WAVEWATCH BY A FOOT DURING THIS TIME AS IT WAS SLOWER BRINGING THE
FRONTAL SYSTEM ACROSS THE AREA. THERE IS THOUGH SOME UNCERTAINTY
WITH THE SEAS DUE TO THE TIMING DIFFERENCES AMONGST THE MODELS.

&&

.HYDROLOGY...
SCT TSTMS THIS AFTERNOON THIS EVENING...MAINLY LOWER HUDSON
VALLEY. COVERAGE IS NOT EXPECTED TO BE LARGE ENOUGH TO PRESENT A
FLOOD TREAT.

SCT SHOWERS/TSTMS WED WILL BE CAPABLE OF PRODUCING LOCALLY HEAVY
RAINFALL...WITH THE BEST CHANCES NORTH/WEST OF NYC. TOTAL BASIN
AVG QPF FOR WED-THU COULD BE 1/4 TO 1/2 INCH...WITH LOCALLY HIGHER
AMTS IN TSTMS.

A MORE ORGANIZED EVENT LATE THU INTO FRI SHOULD PRODUCE AVERAGE
BASIN RAINFALL AMOUNTS CLOSE TO AN INCH...WITH LOCALIZED HIGHER
AMOUNTS. THERE IS THE POTENTIAL FOR TRAINING OF THUNDERSTORMS
WHICH COULD RESULT IN FLASH FLOODING.

FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED
AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...DENSE FOG ADVISORY UNTIL 10 AM EDT WEDNESDAY FOR NYZ081.
NJ...NONE.
MARINE...DENSE FOG ADVISORY UNTIL 10 AM EDT WEDNESDAY FOR ANZ345-350-
     353.

&&

$$
SYNOPSIS...TONGUE
NEAR TERM...TONGUE
SHORT TERM...TONGUE
LONG TERM...DW
AVIATION...MET
MARINE...TONGUE/DW
HYDROLOGY...TONGUE/DW