Area Forecast Discussion
Issued by NWS Upton, NY

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000
FXUS61 KOKX 301326
AFDOKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
926 AM EDT SAT APR 30 2016

.SYNOPSIS...
HIGH PRESSURE BUILDS IN TODAY...THEN SLIDES OFFSHORE TONIGHT. A
WARM FRONT APPROACHES SUNDAY...STALLING OUT TO THE SOUTH OF LONG
ISLAND EARLY NEXT WEEK...WITH WAVES OF LOW PRESSURE RIDING ALONG
IT. HIGH PRESSURE THEN BUILDS IN TUESDAY...THEN SLOWLY SLIDES
OFFSHORE TUESDAY NIGHT. A COMPLEX STORM SYSTEM WILL THEN BRING
UNSETTLED WEATHER TO THE REGION WEDNESDAY THROUGH FRIDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SC CLOUDS ERODING THIS MORNING AS RIDGE BUILDS...ALTHOUGH COULD
SEE SOME OF THESE CLOUDS REDEVELOP AS BOUNDARY LAYER HEATS.

DEEP LAYERED RIDGING BUILDS...WITH ASSOCIATED SUBSIDENCE KEEPING
THINGS DRY. PARTLY TO MOSTLY SUNNY SKY CONDITIONS EXPECTED BASED
ON LATEST TRENDS.

HIGHS TODAY SHOULD BE AROUND 5 DEGREES BELOW NORMAL...UPPER 50S TO
LOWER 60S. THE SEABREEZE SHOULD ALLOW FOR WIND GUSTS UP TO 20 MPH
AT COASTAL AREAS THIS AFTERNOON.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
THE AXIS OF THE DEEP LAYERED RIDGE SLIDES TO THE EAST
TONIGHT...HOW FAST IT DOES SO WILL DETERMINE HOW FAST RAIN MOVES
INTO THE TRI-STATE AFTER MIDNIGHT. MINDFUL THAT THE GFS HAS A BIAS
OF BEING TO PROGRESSIVE WITH DEEP LAYERED RIDGING MOVING OFF THE
ATLANTIC SEABOARD...LEANED TOWARDS SLOWER ECMWF/NAM. KEPT FAR
EASTERN AREAS DRY...AND LIMITED LIKELY POPS TO FAR WESTERN ZONES
LATE TONIGHT. LOWS TONIGHT WERE BASED ON A BLEND OF MET/ECS/MAV
GUIDANCE WITH NAM 2-METER TEMPERATURES...AND SHOULD BE A FEW
DEGREES BELOW NORMAL.

00Z ECMWF IS THE ONLY MODEL WHICH DOES NOT DEVELOP A SECONDARY LOW
OVER THE MID-ATLANTIC STATES SUNDAY NIGHT...THEN TRACK THE LOW S
OF LONG ISLAND MONDAY. THE CMC DOES THIS...IT JUST TRACKS THE LOW
TO THE S OF LONG ISLAND MUCH FASTER THAN OTHER GUIDANCE. THE 00Z
ECMWF IS ALSO THE ONLY MODEL TO NOT HAVE A FRONT MOVE FAR ENOUGH S
MONDAY NIGHT TO PRECLUDE RAIN MONDAY NIGHT INTO TUESDAY AS WAVES
OF LOW PRESSURE RIDE ALONG IT. THIS IS BECAUSE IT IS FARTHER N
THAN OTHER MODELS WITH A 700 HPA SHORTWAVE AND ASSOCIATED
VORTICITY MAXIMA AS THEY TRANSIT THE GREAT LAKES/NORTHEAST SUNDAY
NIGHT-MONDAY. THE 00Z CMC TAKES THE FRONT ABOUT AS FAR S AS THE
NON 00Z-ECMWF MODELS...HOWEVER IT HAS A STRONGER WAVE OF LOW
PRESSURE RIDE ALONG THE FRONT THAN OTHER GUIDANCE. AS A RESULT
DID NOT INCLUDE THE 00Z ECMWF OR CMC-GLOBAL IN THE BLEND OF
GUIDANCE SUNDAY-MONDAY NIGHT...HOWEVER DID USE THE 12Z/29 ECMWF
AS IT WAS MORE CONSISTENT WITH REMAINDER OF 00Z MODEL SUITE.

AS A RESULT...EXPECT PERIODS OF RAIN TO DEVELOP FROM SW TO NE
SUNDAY MORNING...WITH THE RAIN LIKELY CONTINUING SUNDAY NIGHT AND
MONDAY MORNING...BEFORE TAPERING OFF MONDAY AFTERNOON AS THE
AFOREMENTIONED SHORTWAVE EXITS TO THE NE. ALSO WITH THE REGION
PROGGED TO HAVE SHOWALTERS OF -2 TO 2 FROM LATE SUNDAY NIGHT INTO
MONDAY AND TO BE IN A COUPLED UPPER JET STRUCTURE ON MONDAY...HAVE
ADDED A SLIGHT CHANCE OF THUNDER FOR MONDAY. ANY CONVECTION SHOULD
BE OF AN ELEVATED NATURE.

FOR HIGHS SUNDAY...A BLEND OF MAV/MET/12Z ECS GUIDANCE...00Z NAM
AND 12Z ECMWF 2-METER TEMPERATURES...AND A MIX DOWN FROM 975-950
HPA WAS USED PER BUFKIT SOUNDINGS. HIGHS SHOULD BE AROUND 10-15
DEGREES BELOW NORMAL. FOR LOWS SUNDAY NIGHT A BLEND OF 12Z ECS/00Z
MET/MAV GUIDANCE WITH 12Z ECMWF AND 00Z NAM 2-METER TEMPERATURES
WAS USED...WITH VALUES FORECAST TO BE AROUND NORMAL. HIGHS MONDAY
SHOULD BE AROUND 5-10 DEGREES ABOVE NORMAL...CONSISTENT WITH A
BLEND OF MIX DOWN FROM 975-900 HPA...00Z NAM AND 12Z ECMWF 2-METER
TEMPERATURES...AND A MIXTURE OF 00Z MAV/MET AND 12Z ECS GUIDANCE.

WEAK RIDGING BUILDS IN MONDAY NIGHT...SO IT SHOULD BE DRY. LOWS
WERE BASED ON A BLEND OF 00Z NAM AND 12Z ECMWF 2-METER
TEMPERATURES WITH A BLEND OF MEX/MEN/EKD/12Z ECE/ECM GUIDANCE.
LOWS SHOULD BE NEAR TO SLIGHTLY BELOW NORMAL.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
IT SHOULD BE DRY ON TUESDAY AS THE LOW LEVELS SHOULD BE
SUFFICIENTLY DRY TO PRECLUDE PRECIPITATION EVEN WITH A 700-500 HPA
NORTHERN STREAM SHORTWAVE CROSSING THE REGION.

THERE REMAINS QUITE A BIT OF VARIANCE IN MODEL SOLUTIONS TUESDAY
NIGHT-FRIDAY. IN A SWITCH FROM THE 12Z RUNS...THE 00Z ECMWF NOW
ENDS UP WITH THE CUTOFF LOW TO THE N BY THE END OF THE WEEK AND
THE GFS HAS IT TO OUR S. THE REASONS DEAL WITH DIFFERENCES IN
HANDLING A CUTOFF LOW OVER HUDSON BAY AND SHORTWAVE ENERGY
TRACKING DOWN ITS SW FLANK.

GIVEN THE UNCERTAINTY LIMITED POPS TUESDAY NIGHT TO SLIGHT
CHANCE...THEN POPS WEDNESDAY-THURSDAY (THIS IS THEN GENERAL TIME
FRAME WHEN REGARDLESS OF SOLUTION THE MODELS INDICATED THE BEST
CHANCE FOR PRECIPITATION IN ALL SOLUTIONS) TO LOW END
CHANCE...WITH SLIGHT CHANCE POPS THURSDAY NIGHT AND FRIDAY.

THIS IS A VERY LOW CONFIDENCE FORECAST THROUGHOUT THE LONG TERM
PERIOD DUE TO THE LARGE MODEL SPREAD AND RUN TO RUN
VARIABILITY. THIS UNCERTAINTY IS AMPLIFIED BY THE MODELS
FORECASTING CUTOFF LOWS...WHICH IS AN ITEM THEY ALL HAVE A LOWER
THAN AVERAGE SKILL AT FORECASTING.

FOR TEMPERATURES TUESDAY-FRIDAY THE SUPER BLEND WAS USED. FOR NOW
FORECASTING BELOW NORMAL HIGHS AND LOWS A FEW DEGREES ABOVE
NORMAL IN THIS TIME FRAME.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
A RIDGE OF HIGH PRESSURE SHIFTS THROUGH TODAY.

VFR. NE WINDS UNDER 10KT BCMG SE THIS MORNING. SEA BREEZES THIS
AFTN WITH SE-S WINDS AROUND 10KT.

.OUTLOOK FOR 12Z SUN THROUGH WED...
.SUN-MON...RAIN WITH MVFR OR LOWER CONDS. ESE/E WIND GUSTS OF 20 TO
25 KT POSSIBLE SUNDAY AFT FOR CITY/COASTAL TERMINALS.
.TUE...VFR.
.WED...CHANCE OF RAIN WITH WITH MVFR OR LOWER CONDS.

&&

.MARINE...
OCEAN SEAS HAVE SUBSIDED SOMEWHAT...BUT STILL HOVER AROUND 5
FEET. WILL MAINTAIN THE SCA FOR NOW...WHICH IS IN EFFECT UNTIL
16Z. NON OCEAN WATERS REMAIN TRANQUIL...LIGHT WINDS AND 1 FT OR
LESS SEAS/WAVES.

A RELAXED PRESSURE GRADIENT OVER THE WATERS WILL KEEP WINDS TO 10
KT OR LESS OVER THE WATERS THROUGH TONIGHT. SUB-SCA CONDITIONS
THEN CONTINUE FOR ALL WATERS THROUGH AT LEAST SUNDAY MORNING.
WINDS AND SEAS THEN PICK UP DURING THE AFTERNOON AS THE PRESSURE
GRADIENT TIGHTENS AHEAD OF AN APPROACHING STORM.

IT LOOKS LIKE SCA WILL BE NEEDED FOR SUNDAY AFTERNOON AT LEAST ON
THE OCEAN...AND MAYBE FOR THE SOUND. A BETTER CHANCE FOR 25KT
GUSTS ON THE SOUND AND PERHAPS FOR THE HARBOR AND BAYS ARRIVES
SUNDAY NIGHT. SCA CONDITIONS OTHERWISE ON THE OCEAN THROUGH AT
LEAST MONDAY...AND POSSIBLY INTO A PORTION OF MONDAY NIGHT AS SEAS
SLOWLY SUBSIDE.

A WEAK PRESSURE GRADIENT THEN MAINTAINS SUB-SCA CONDITIONS ON ALL
WATERS THROUGH WEDNESDAY.

&&

.HYDROLOGY...
IT SHOULD BE DRY THROUGH AT LEAST THIS EVENING.

FROM AROUND 3/4-1 INCH OF RAIN IS FORECAST FROM LATE TONIGHT INTO
MONDAY EVENING...WITH LOCALLY HIGHER AMOUNTS POSSIBLE. AT THIS
TIME THERE IS A LOW RISK OF PONDING OF WATER ON ROADWAYS FOR
AREAS EXPERIENCING LOCALLY HEAVY RAINFALL.

THERE IS ALSO A CHANCE FOR ANOTHER SIGNIFICANT RAINFALL DURING
THE MIDDLE TO LATER PART OF NEXT WEEK.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL NOON EDT TODAY
     FOR ANZ350-353-355.

&&

$$
SYNOPSIS...MALOIT
NEAR TERM...MALOIT/PW
SHORT TERM...MALOIT
LONG TERM...MALOIT
AVIATION...JC
MARINE...JC/MALOIT/PW
HYDROLOGY...MALOIT


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