926
FXUS61 KALY 302040
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
440 PM EDT Wed Jul 30 2025

.SYNOPSIS...
After a hot and humid day today, a slow moving front tomorrow
stalls over the mid or lower Hudson Valley. Given the moisture
rich environment and a disturbance tracking along the front,
rain will overspread the majority of the area tomorrow afternoon
into tomorrow night with rain turning heavy at times across the
mid-Hudson Valley into Litchfield County where isolated to
scattered flash flooding may occur. Tranquil and much cooler
weather follows for Friday and Saturday before temperatures turn
warmer early next week.

&&

.DISCUSSION...
Afternoon temperatures today have risen into the low to mid 90s
and combined with high humidity values, the heat index per ASOS
and the NYS Mesonet are in low 100s in the mid-Hudon Valley with
mid to upper 90s in the Hudson Valley where we have the heat
advisory. The latest satellite imagery and sfc observations shows
a low-level convergence area focused within the mid and lower
Hudson Valley where a line of isolated to widely scattered
showers have developed. While mid-level lapse rates are quite
poor at only 5-5.5C/km, the heat and humidity has supported high
SB CAPE values ranging 2-2.5k J/kg per the SPC mesoscale
analysis with effective shear 30-40kts. So, should any stronger
updrafts develop especially where terrain can provide additional
forcing for ascent, an isolated severe storm is not ruled out.
SPC maintains its marginal risk for severe weather across much
of the area today, outside of the south/western Adirondacks.
Further north, we are monitoring the main cold front sinking
south out of the North Country and approaching the Upper Hudson
Valley late this afternoon. There are a few isolated thunderstorms
along this boundary and these storms can track into the Upper
Hudson Valley this afternoon but again, poor lapse rates and
lower SB CAPE should limit the severe threat here.

Heading into tonight and tomorrow morning, this boundary will
continue tracking southward as a shortwave and associated sfc
low amplifies in the Ohio Valley. As moisture streams eastward
and isentropic lift becomes enhanced across the front, expecting
areas of rain to develop initially over western and central NY
late tonight before spreading into eastern NY and western New
England by 12 - 15 UTC. While the low-level boundary continues
to push southward settling across the mid and lower Hudson
Valley by midday or early afternoon, stratiform rain on the cool
side of the front will become widespread across the region by
early afternoon as the shortwave continues to slowly advance
eastward. The primary area of concern for any flooding
potential will be focused across mainly the mid-Hudson Valley
and Litchfield County/southern Berkshire County where the slight
risk (level 2 of 4) in the WPC Excessive Rainfall Outlook
highlights for isolated to scattered flash flooding potential.
Given rather dry antecedent conditions this summer, widespread
flooding is not anticipated; however, we issued a Flood Watch in
Litchfield County from 18 UTC Thurs to 18 UTC Fri where high
rainfall rates from training convection is possible. See our
hydro discussion for more details on the heavy rain and flooding
potential.

Stratiform rain continues Thursday night after Midnight but
will be winding down as the secondary low tracking along our
boundary exits into New England. Lingering rain showers Friday
morning mainly along and east of the Hudson River diminish from
northwest to southeast by early afternoon. Much cooler and much
lower humidity follow for Friday as northerly winds in the wake
of the boundary usher in a drier and cool Canadian air mass
with daytime highs struggling to get out of the upper 60s to low
70s. We remain cool into Friday night as skies gradually clear
and support radiational cooling with high pressure building into
the Northeast. Great night to open up the windows as
temperatures cool into the 40s and 50s with low humidity.

Very pleasant Saturday in store for eastern NY and western New
England as high pressure takes control of the region supporting
plenty of sunshine and very comfortable temperatures in the 70s
to around 80 and low humidity once again. Tranquil weather
continues Sunday into early next week as temperatures trend
warmer and back to seasonable temperatures for early August with
persistent dry conditions.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
Through 18z Thursday...VFR conditions prevail across all terminals
and will continue throughout much of the 18z TAF period as high
pressure remains dominant. Despite the passage of a weak cold
frontal boundary, precipitation is not expected this afternoon into
this evening, but will monitor the potential for an isolated shower
or thunderstorm to impact especially KPOU through this afternoon and
make any amendments that are necessary.

With clouds on the increase tonight ahead of a potent upper-level
system, fog development will be mitigated. Towards the end of the
period, rain from said disturbance and the aforementioned cold front
that will become stationary to our south looks to begin at KPOU and
KPSF. There are still uncertainties pertaining to timing of onset so
PROB 30s were included at both sites before a prevailing rain in the
last hour of the period. MVFR visibilities will be possible
especially within the last hour or so of the 18z cycle given the
potential for rain to become moderate to locally heavy. Winds
throughout the period will begin out of the northwest but will switch
to the northeast overnight at the passage of the front. Sustained
speeds will generally fall below 10 kt.

Outlook...

Thursday Night: High Operational Impact. Likely SHRA.
Friday: Moderate Operational Impact. Chance of SHRA.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: No Operational Impact. NO SIG WX.
Sunday Night: No Operational Impact. NO SIG WX.
Monday: No Operational Impact. NO SIG WX.

&&

.HYDROLOGY...
Isolated to scattered flash flooding will be monitored tomorrow
afternoon through tomorrow evening as our boundary stalls over
the mid and lower Hudson Valley with PWAT values rising to 1.5 -
2.25 inches near and south of the boundary (or 2 standard
deviations above normal). Given a ~90 to 100kt 300hPa jet
positioned over northern New England, strong forcing for ascent
in its equatorward entrance region will support strong forcing
for ascent focused along the boundary. As a shortwave from the
Ohio Valley tracks along the boundary and encounters the
stronger jet dynamics, a secondary low develops and likely
enhances frontogenesis in the 850 - 700hPa layer as the low and
mid-level convergence strengthens. Given the highly moisture
rich environment and some weak available instability, high
resolution guidance suggest rainfall rates become higher through
the afternoon into the evening hours with the HREF showing
rates up to 1-2 inch per hour rainfall rates mainly from 18 UTC
to 03 UTC. The HREF also shows 30 - 50% chance for 3-hrly
rainfall amounts exceeding 1 inch during this window. As the
secondary low approaches late P.M into the evening and the low-
level southeasterly jet reaches 25 - 40kts, we also notice the
potential for a training line of convection to develop just to
the north of the boundary or on the "cool side of front" along
the southern fringe of the stratiform rain. This is supported as
the low-level jet directs the anomalous moisture plume towards
the stalled east-west oriented front and the forward
propagating corfidi vectors are nearly parallel to the mean
cloud layer winds which can support the previously mentioned
high rainfall rates repeatedly impacting a given area. Despite
the potential for high rainfall rates, it should be noted that
the coverage of any resulting flash flash flooding should be
isolated to scattered as the 1 hour and 3 hour flash flood
guidance is quite high ranging 2 - 3" and 2.5 - 3.5",
respectively.

Given all these reason, we coordinated with BOX/OKX to issue a
Flash Flood Watch for Litchfield County from 18 UTC Thurs to 18
UTC Fri where PMM/LPMM and max rainfall rates from the HREF
show the highest values. Less confidence on coverage of flash
flooding in Ulster/Dutchess County where the CAMs are less
bullish on rainfall rates but given potential for upslope
enhancements in the Catskills plus the training convection, the
watch may be expanded in future forecast updates.

The heaviest rain looks to wind down by 03 - 06 UTC as the
secondary low exits to into eastern New England with stratiform
rain showers lingering into Friday morning. Still uncertainty
on exactly where the heaviest rainfall axis will set up but
total rainfall amounts look to range 1 - 3 inches with the
highest amounts across the mid-Hudson Valley into NW CT. Locally
up to 3-5 inches should heavy rain persist over a given area.
Precipitation decreases heading north and west of the Capital
District where a tight north/west gradient looks to set- up.

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT this evening for CTZ001-013.
     Flood Watch from Thursday afternoon through Friday afternoon
     for CTZ001-013.
NY...Heat Advisory until 8 PM EDT this evening for NYZ040-041-049-
     050-052-053-059>061-064>066-083-084.
MA...None.
VT...None.

&&

$$

SYNOPSIS...Speciale
DISCUSSION...
AVIATION...Gant
HYDROLOGY...Speciale