AFDOKX

Area Forecast Discussion
National Weather Service New York NY
757 PM EDT Wed Apr 30 2025

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH THURSDAY/...
Surface high pressure and upper level ridging build over the area 
tonight and slides off to the east during the day Thursday
brining dry and seasonably mild conditions. 

Low temperatures tonight will fall into the upper 30s and 40s
for much of the area. Good radiational cooling conditions across
interior valleys and LI pine barrens should allow temps to drop
into the lower to mid 30s with patchy frost development.
Meanwhile, the NYC/NJ metro area where lows fall into the 50s. 

Highs on Thursday, will be in the 60s and lower 70s.

&&

.SHORT TERM /THURSDAY NIGHT/...
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.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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 storm total 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.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
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.

NW to N winds around 10 kt or less will continue to diminish
through the night. Some outlying terminals will become light 
and variable late tonight. Light ENE to E winds early Thursday 
morning become SE late in the morning into Thursday afternoon.

 ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

Isolated gusts of 15 to 20 kt possible through 02Z.

.OUTLOOK FOR 00Z FRIDAY THROUGH MONDAY...

Thursday Night: VFR initially. MVFR or lower possible late. 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

&&

.MARINE...
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.

&&

.FIRE WEATHER...
Elevated fire weather conditions will quickly dissipate this 
evening with weakening winds and moderating RH values as high 
pressure builds into the area tonight into Thursday. 

Light and variable winds early Thursday AM with patchy frost 
across the interior and LI barrens, increasing to southeasterly
5 to 10 mph by late morning/early afternoon. RH values drop to 
25-35 percent by late morning, increasing to the 40-45 percent 
along the coast by Thursday afternoon with strengthening onshore
flow. High temperatures in the lower to mid 60s.

&&

.HYDROLOGY...
Low predictability on rainfall amounts and hydrologic concerns Sun 
thru early next week, dependent on progressiveness of a frontal 
system thru the area.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$

SYNOPSIS...BC/NV
NEAR TERM...BC/NV
SHORT TERM...BC
LONG TERM...NV
AVIATION...JP
MARINE...BC/NV
FIRE WEATHER...
HYDROLOGY...BC/NV