444
FXUS61 KOKX 130621
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
221 AM EDT TUE AUG 13 2013
.SYNOPSIS...
A COLD FRONT WILL APPROACH FROM THE WEST THIS MORNING...THEN MOVE
ACROSS THIS AFTERNOON AND EVENING. A LARGE AREA OF HIGH PRESSURE
WILL BUILD IN BEHIND THE FRONT THROUGH THE END OF THE WORK WEEK...
AND REMAIN THROUGH MUCH OF THE WEEKEND. LOW PRESSURE WILL APPROACH
LATE IN THE WEEKEND INTO MONDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
HIGH/MID LEVEL CLOUDS ARE BEGINNING TO MOVE IN AND THICKEN...SO
OVERNIGHT TEMPS SHOULD STAY STEADY OR SLOWLY RISE. EARLIER
RADIATIONAL COOLING HAS ALSO RESULTED IN DEVELOPMENT OF LOW
STRATUS OVER EASTERN CT/LONG ISLAND...ALONG WITH SOME
COASTAL FOG.
CONTINUE TO EXPECT THE NEXT FEW HOURS TO BE DRY UNTIL A 700-500
HPA SHORTWAVE MOVES INTO WESTERN PARTS OF THE TRI-STATE BY 12Z
TUESDAY. DO BRING IN CHANCE /WEST/ TO SLIGHT CHANCE POPS FOR ALL
BUT FAR EASTERN PARTS OF THE CWA LATE TONIGHT IN RESPONSE. WITH
MEAGER SUPPORT FOR THUNDER...LIMITED CHANCES OF THUNDER TO SLIGHT
CHANCE THROUGHOUT.
USED A BLEND OF FAIRLY SIMILAR MAV AND MET GUIDANCE FOR
LOWS...WITH VALUES NEAR TO SLIGHTLY ABOVE NORMAL EXPECTED.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
THE REGION WILL BE IN THE RIGHT REAR QUADRANT OF A 100+ KNOT 250
HPA JET TUESDAY...WITH ASSOCIATED DIVERGENCE ALOFT...COUPLED WITH
THE APPROACHING/PASSING COLD FRONT SHOULD PROVIDE SUFFICIENT
FORCING TO WARRANT LIKELY POPS ACROSS THE TRI-STATE.
HOWEVER...WITH CAPE FORECAST OF ONLY 500-1500 J/KG AND LIFTED
INDICES DOWN TO ONLY AROUND -2/-3 HAVE CAPPED PROBABILITY OF THUNDER
AT CHANCE. THE LACK OF INSTABILITY ALSO WILL SERVE TO LIMIT THE
SEVERE THREAT...ESPECIALLY OVER EASTERN LONG ISLAND/CT WHICH ARE
NO LONGER IN A SLIGHT RISK FOR SEVERE THUNDERSTORMS PER SPC.
HOWEVER STILL WILL HAVE 35-45 KT OF SHEAR OVER THE AREA WITH BULK
RICHARDSON NUMBERS 25-45 IN THE HIGHER CAPE AREA...SO CONVECTIVE
LINE SEGMENTS WITH GUSTS TO SEVERE LEVELS CANNOT BE RULED
OUT...ESPECIALLY OVER WESTERN ZONES. BASED ON THIS WILL ADJUST HWO
TO REFLECT SEVERE THREAT PER LATEST SPC OUTLOOK.
DO GET COUPLED JET STRUCTURE OVER EASTERN ZONES TUESDAY EVENING
JUST AHEAD OF COLD FRONT...WARRANTING LIKELY POPS THERE...WITH POPS
TAPERING OFF FROM NW TO SE THROUGH THE NIGHT. BASED ON FRONTAL
TIMING...WOULD EXPECT SEVERE THREAT TO BASICALLY BE OVER WITH BY
TUESDAY EVENING.
FOR HIGHS TUESDAY USED A BLEND OF MIXING DOWN FROM 950 HPA NEAR
THE IMMEDIATE COAST AND 925 HPA ELSEWHERE PER BUFKIT
SOUNDINGS...WITH NAM 2-METER TEMPERATURES AND MAV AND MET GUIDANCE
- WITH VALUES EXPECTED TO BE A FEW DEGREES BELOW NORMAL. USED A
BLEND OF MAV/MET GUIDANCE FOR LOWS TUESDAY NIGHT WITH VALUES ALSO
A FEW DEGREES BELOW NORMAL.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
MODELS IN GOOD AGREEMENT THROUGH THE LONG TERM PERIOD WITH A LARGE
AREA OF HIGH PRESSURE BUILDING INTO THE REGION ON WEDNESDAY...AND
REMAINING OVER THE AREA THROUGH MUCH OF THE WEEKEND. THIS WILL
TRANSLATE INTO A DRY FORECAST.
12Z MODEL GUIDANCE IS SHOWING A WAVE OF LOW PRESSURE DEVELOPING
SOUTH OF THE REGION AND MOVING OVER THE REGION...IMPACTING THE AREA
SOMETIME DURING SUNDAY NIGHT AND MONDAY TIME FRAME. WILL START TO
INTRODUCE POPS SUNDAY NIGHT AND MONDAY...BUT WILL KEEP THE POPS AT
CHANCE OR SLIGHT CHANCE.
TEMPERATURES WILL BE SLIGHTLY BELOW NORMAL THROUGH THE PERIOD...WITH
HIGHS IN THE UPPER 70S AND LOWER 80S EACH DAY. OVERNIGHT LOWS ALSO
REMAIN SLIGHTLY BELOW NORMAL...WITH LOWS GENERALLY IN THE 50S AND
60S. A FEW OUTLYING LOCATIONS COULD SEE LOWS FALL INTO THE UPPER 40S
WEDNESDAY NIGHT.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
A COLD FRONT APPROACHES FROM THE WEST WITH LOW PRESSURE DEVELOPING
ALONG IT AND MOVING ACROSS THE REGION TODAY. THE LOW AND FRONT
PUSH EAST OUT OF THE AREA TONIGHT.
VFR INITIALLY FOR MOST TERMINALS WITH LOCALIZED MVFR TO VLIFR
CONDITIONS OUTSIDE OF THE CITY TERMINALS. THE TREND WILL BE
LOWERING TO MVFR/IFR WITH INCREASING COVERAGE OF SHRA/TSRA. BEST
TIMING FOR BULK OF THIS ACTIVITY IS 13-21Z FROM WEST TO EAST WITH
1-2 HRS UNCERTAINTY. COVERAGE DECREASES THEREAFTER.
GUSTY WINDS POSSIBLE WITH STRONGER THUNDERSTORMS. ALSO THE BETTER
CHANCE OF CONVECTION WILL BE FROM THE NEW YORK CITY TERMINALS AND
NORTH AND WEST.
WINDS S-SE UNDER 10 KT FOR MUCH OF THE TAF PERIOD...BECOMING
WESTERLY AND INCREASING TO 10-15 KT BY LATER TUESDAY EVENING.
OUTLOOK FOR 00Z WEDNESDAY THROUGH SATURDAY...
.TUESDAY NIGHT...SCT SHOWERS/TSTMS ENDING IN THE EVENING WITH
IMPROVING CONDITIONS. WIND SHIFTS TO THE NORTHWEST.
.WEDNESDAY-SATURDAY...VFR.
&&
.MARINE...
VERY LIGHT PRESSURE GRADIENT OVER THE REGION WILL KEEP WINDS 10 KT
OR LESS AND SEAS 2 FT OR LESS ON THE COASTAL OCEAN WATERS AND 1
FT OR LESS ELSEWHERE THROUGH TUESDAY EVENING. WINDS GENERALLY
INCREASE TO 10-15KT OUT OF THE NW WITH SOME GUSTS TO 20 KT BEHIND
A COLD FRONT OVERNIGHT TUESDAY NIGHT - BUT STILL SHOULD REMAIN
BELOW SCA LEVELS.
A POST-FRONTAL NW FLOW ON WEDNESDAY WILL FEATURE WIND GUSTS RIGHT
AROUND 20 KT...WITH SEAS BELOW 5 FT. HIGH PRESSURE THEN BUILDS
ACROSS THE WATERS FOR THE END OF THE WEEK WITH WINDS 10 KT OR LESS.
SEAS REMAIN BELOW 5 FT.
&&
.HYDROLOGY...
GENERALLY 1/3-2/3 OF AN INCH OF BASIN AVERAGE RAINFALL IS EXPECTED
FROM LATE TONIGHT THROUGH TUESDAY NIGHT WITH...LOCALLY HIGHER
AMOUNTS POSSIBLE. NOTING PRECIPITABLE WATERS FORECAST TO APPROACH
2 INCHES...LOCALLY HEAVY RAINFALL IS POSSIBLE. HOWEVER THE
RELATIVELY FAST MOTION OF THE STORMS SHOULD LIMIT ANY FLOODING TO
THE MINOR URBAN/POOR DRAINAGE VARIETY TUESDAY/TUESDAY EVENING.
DRY WEATHER THEN PREVAILS THROUGH AT LEAST THE END OF THE WEEK.
&&
.EQUIPMENT...
THE NOAA ALL HAZARDS WEATHER RADIO TRANSMITTER IN NEW YORK CITY
IS OFF THE AIR...AND UNAVAILABLE UNTIL FURTHER NOTICE.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...BC/MALOIT
NEAR TERM...MALOIT/LN
SHORT TERM...MALOIT
LONG TERM...BC
AVIATION...JM
MARINE...BC/MALOIT
HYDROLOGY...BC/MALOIT
EQUIPMENT...