384
FXUS61 KOKX 301946
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
346 PM EDT Wed Apr 30 2025
.SYNOPSIS...
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High pressure will be in control through Thursday. A warm front
approaches Thursday night and lifts through the region Friday
morning. A cold front approaches late Saturday into Saturday
night, with a wave of low pressure developing along it as does
so. This frontal system may linger near the area through early
next week, as a cutoff upper low develops to the southwest.-- End Changed Discussion --
&&
.NEAR TERM /THROUGH THURSDAY/...
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Surface high pressure and upper level ridging build over the area
tonight and slides off to the east during the day Thursday. Expect
dry conditions through Thursday. Low temperatures tonight will fall
into the upper 30s and 40s. The exception will be in the NYC metro
area where lows fall into the 50s. Highs on Thursday, will be in the
60s and lower 70s.-- End Changed Discussion --
&&
.SHORT TERM /THURSDAY NIGHT/...
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As the high moves further east Thursday night, low pressure
will move into the Great Lakes region. An associated warm front is
forecast to move into the region bringing increased cloud cover
along with a chance for showers Thursday night into early Friday
morning. It appears that the better chances for any rainfall will
remain west of NYC, but there will still be a chance across the
entire region. It will be a bit more mild with lows in the
upper 40s and 50s.-- End Changed Discussion --
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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Good agreement in east coast upper ridging sliding east on Friday,
with a couple of northern stream shortwaves digging a trough from
the Canadian plains into the mid Mississippi River Valley Friday
into Saturday. Model spread increases heading through the weekend
into next week on the timing and location of the base of this deep
trough evolving into a cutoff closed low. Better agreement on the
northern portion of the trough pivoting through the NE US Sat Night
into Monday.
ECMWF/GEPS ensembles and majority of AI models (notably trained on
the ECMWF ERA5 dataset) develop/hang the cutoff low to the SW of the
region across the Tennessee R/Ohio R valley this weekend thru early
next week as an omega blocking pattern develops across the Eastern
US into Western Atlantic. The result being a frontal system
approaching Friday, with the cold front stalling to the west of the
region and strong Canadian maritime high to the NE, resulting in a
persistent Atlantic/sub-tropical moisture flow with rounds of
shower/embedded tsra activity as waves of low pressure ride up the
stalled cold front Sat thru midweek. NBM ensemble 90th percentile
signaling 72hr rainfall potential of 3", similar to ECMWF ensemble
50th percentile stormtotal Fri thru Wed. Of course, low
predictability on QPF amounts at this point, but a plausible
basin averaged outcome if this stalled scenario pans out.
Meanwhile, GFS/GEFS ensemble is a more progressive scenario, with a
farther SE development of the cutoff upper low off the SE US coast,
which allows for the approaching frontal system (warm frontal
passage on Friday) and then gradual cold frontal approach/passage
Sat/Sat eve with accompanying shra/tsra activity. In its wake
surface high pressure builds in as ridging surface/aloft build
overhead in the split flow for Sun thru midweek. A much more
progressive and drier scenario.
So overall, a low confidence forecast for back half of the weekend
into early next week at this point based on the model divergence
discussed above.
Better model agreement and higher confidence in Fri/Sat forecast
with warm frontal passage Fri AM bringing a few showers, advecting
in a warm/moist airmass on deep SW flow. S/SW flow and deep mixing
will likely allow temps west of the Hudson to rise well into the
80s, while southern/eastern coastal areas remain in the 60s to
around 70. Have leaned towards a blend of NBM deterministic and
NBM 50th for temps west of the Hudson based on above synoptic
setup, and close to NBM deterministic for coast with maritime
influence. NBM deterministic is running in the 25th quartile of
the ensemble distribution.
Pre-frontal trough approaches western portions of the area Fri
aft/eve. Potential for sct shra/isolated tsra activity for NYC and
points N&W in a weakly forced, but marginally unstable/modest shear
environment. A more stable airmass along the coast will likely have
any convection dissipating as it overspreads the coast and
encounters this environment. Conversely, could be dealing with
stratus/fog development for southern and eastern coastal areas late
Friday into Sat with moist onshore flow over cold waters (lower 50
SSTs). CSU MLP indicating a marginal severe threat, which seem
conditionally possible with a more distinct shortwave trigger and
resultant stronger shear/instability profile.
Better chance for organization of scattered shra/tsra activity ahead
of/along cold front late Sat/Sat Eve for NYC and points NW with
approach of northern shortwave in a marginally unstable and strong
deep layer shear environment. This convective scenario will
ultimately will be predicated on evolution of northern trough and
cutoff. Although airmass is similar on Friday to Saturday, potential
for more in the way of convective debris on Saturday limiting full
insolation. Have leaned towards a blend of NBM deterministic and NBM
50th for temps west of the Hudson based on above synoptic setup
(upper 70s), and close to NBM deterministic for coast with maritime
influence (60s to around 70). NBM deterministic once again is
running in the 25th quartile of the ensemble distribution.-- End Changed Discussion --
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
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High pressure moves across the region tonight and then offshore
on Thursday. A warm front approaches late in the TAF period.
VFR conditions are expected through the TAF period.
Winds are NW and gusting. The winds become more northerly
tonight with gusts diminishing. The winds become more easterly
Thursday.
Wind speeds near 10-15 kt this afternoon into early this evening.
Gusts near 25 kt initially will be closer to 20 kt heading into
early this evening. Then wind speeds near 5-10 kt tonight
through Thursday with no more gusts expected. Winds are generally
SE late Thursday morning into Thursday afternoon.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Wind gust end time could be 1-2 hours off from TAF.
.OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY...
Thursday Afternoon - Thursday Night: VFR initially. MVFR or
lower possible at night. A chance of showers.
Friday: MVFR or lower possible. A chance of showers and
thunderstorms. Southerly wind gusts 15-20 kt afternoon into evening.
Saturday: MVFR or lower possible. A chance of showers and
thunderstorms. SW wind gusts 15-20 kt afternoon into evening. Wind
direction becomes more westerly into the evening.
Sunday: MVFR or lower possible. A chance of showers.
Monday: MVFR or lower possible. A chance of showers. NE wind gusts
15-20 kt day into evening.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
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Conditions will remain below small craft levels through Thursday
night as high pressure remains near the region.
Marginal S/SW SCA gusts possible on the ocean Fri aft/eve with
approach of pre-frontal trough and then once again Sat aft/eve with
approach of cold front. More confidence in SCA ocean seas developing
Sat aft/eve and lingering into Sunday based on persistent S/SW flow.
Low predictability on SCA conds for Sun thru early next week based
on progression of a frontal system through the region.-- End Changed Discussion --
&&
.FIRE WEATHER...
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An elevated risk of fire spread remains possible this evening with
NW winds gusting into the teens and lower 20 mph range along with
min RH levels around 20 to 30 percent. Special Weather Statements
have been collaborated with state agencies and remain posted for all
of our NY, NJ, and CT zones today.-- End Changed Discussion --
&&
.HYDROLOGY...
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Low predictability on rainfall amounts and hydrologic concerns Sun
thru early next week, dependent on progressiveness of a frontal
system thru the area.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...BC/NV
NEAR TERM...BC
SHORT TERM...BC
LONG TERM...NV
AVIATION...JM
MARINE...BC/NV
FIRE WEATHER...
HYDROLOGY...BC/NV