482
FXUS61 KALY 081712
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
112 PM EDT Mon Jul 8 2024

.SYNOPSIS...
High pressure will bring partly to mostly sunny, hot and
mainly dry weather today. The humidity increases tonight through
Tuesday ahead of a frontal boundary near southern New York and New
England as chances for showers and thunderstorms increase.  A warm
front lifts north of the region Tuesday night into Wednesday, as the
moisture from post tropical Beryl moves into the region with
numerous showers and scattered thunderstorms into Thursday with some
locally heavy rainfall.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
**Heat Advisory for the mid Hudson Valley, southern Taconics and
 Litchfield County noon through 8 PM today**

Sunny to mostly sunny across the region and area 12Z soundings
show stability across much of the area but some marginal
instability in southern areas. There is still a chance for an
isolated shower or storm in the eastern Catskills to mid Hudson
Valley later this afternoon. Just minor adjustments to
temperatures and sky cover through this afternoon.

PREVIOUS DISCUSSION:
A frontal boundary along the eastern New England Coast and
southern NY will potentially focus some isolated
showers/thunderstorms late in the day near the eastern
Catskills, mid Hudson Valley and southwest of the Capital
Region. The 3-km / 12-km NAM was a bit more robust with the
coverage compared to the 3-km HRRR. Some of the convection that
may pop up is due to the differential heating between the
mountains and valleys. MLCAPEs will be mainly less than 750 J/kg
with dewpoints in the lower to mid 60s.

H850 temps will be a little above normal in the +17C to +19C
range. With good mixing, expect max temps close to an EC/MAV/NBM
blend with upper 80s to lower 90s in the valleys, and upper 70s
to mid 80s over the mtns. The combination of the heat and
moderate humidity levels will yield some heat indices in the mid
90s to spotty upper 90s in the mid Hudson Valley of Dutchess and
eastern Ulster Counties, the southern Taconics and Litchfield
County in NW CT. The Litchfield Hills may fall short but to keep
a clear message and based on the collaboration with WFO BOX
will keep the advisory up noon to 8 pm for all of NW CT.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
Tonight...the frontal boundary moves towards southwest New
England over NW CT and the Berkshires and the mid Hudson Valley.
A weak mid level disturbance in the southwest flow may continue
a few showers and thunderstorms as far north at the Capital
District and the mid Hudson Valley until midnight or so. Some
low stratus and patchy fog will likely develop over portions of
the region. It will become more humid with lows in the 60s to
lower 70s. A few upper 50s are possible in the Adirondack Park.

Tue...The southwest flow strengthens aloft with the front from
the mid Atlantic States northeast through southern NY into New
England. A weak wave or mid level short-wave moving along the
boundary will focus some isolated-scattered and thunderstorms.
SPC has placed our New England zones in a Level 1 out of 5
Marginal Risk. The mid level flow increases to 40-50 KT with
some multi-cells or isolated super cell possible. The heat and
humidity increases with sfc dewpoints in the 60s to lower 70s.
Heat indices may reach the 95-100F in the Capital District south
down the mid Hudson River Valley into NW CT. The question will
be if any convection fires up and cloud cover keeping temps
down slightly. We may need another heat advisory for the
afternoon. In terms of the convection...MLCAPEs based on some of
the CAMS will be in the 500-1000 J/kg range with PWATs rising
to 1.5-2.0". Some locally heavy rainfall and isolated damaging
wind gusts/wet microbursts will be possible. Max temps will
range from the upper 80s to lower 90s in the lower elevations
with upper 70s to mid 80s over the hills and mtns.

Tue night into Wednesday...the frontal boundary interacts with
the remnant circulation of TC Beryl. The mid level flow flattens
and becomes zonal with Post Tropical Beryl over the lower-mid
MS River Valley. The low-level warm advection increases as an
influx of tropical moisture occurs. Scattered showers and some
isolated thunderstorms increase Tue night with muggy conditions
with lows in the 60s to lower 70s.

The threat increases for heavy rain and the threat for isolated
instances of flash flooding on Wed. The antecedent soil
conditions are not wet over the HSA, outside the southern 3
counties that were soaked a few days back (Ulster, Dutchess and
Litchfield). However, the PWATS increase to 1 to 2+ STDEVs above
normal based on the NAEFS/GEFS ahead of the Post Tropical Beryl
over the Midwest. The Marginal to Slight Risk for excessive
rainfall issued by WPC looks warranted for Wed-Wed Night. Bands
or clusters of showers and thunderstorms should develop based on
the ensembles and deterministic guidance. The EC Ensembles have
high probabilities of 50-80% for 1" or greater amounts of
rainfall from roughly the Mohawk Valley northwest between 12Z
WED to 12Z Thu. The 2" Probs are in the Adirondack to Lake
George corridor with 30-50% chances from the EC ensembles. The
footprint of the heavy rainfall varies on the medium range
guidance but there is a consensus that it could be the northern
third to half of the forecast area. Also, a threat for strong
thunderstorms exists along or south of the warm front WED pm
over the eastern Catskills, mid Hudson Valley and southwest New
England. LCL heights will be low and MLCAPES will be 500-1000
J/kg. 0-6 km shear will be increasing to 40-50 KT. A wind damage
or isolated tornado threat is possible in those areas. SPC has
a Marginal Risk in these areas. The flash flood threat will be
tied to any training or intense rainfall rates. Max temps due to
clouds and rain were lowered this cycle with 70s to lower/mid
80s.

The heavy rain threat increases Wed night as the remnant
circulation of Beryl tracks into the eastern Great Lakes
Region. The warm front move north/northeast into northern NY and
northern New England. Periods of heavy rain continue especially
north of the I-90 corridor. Highest probs continue there. It
will be humid with lows in the 60s to lower 70s. See our hydro
section for more details on rainfall and hydro impacts.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Confidence continues to increase in the probability of eastern New
York and western New England remaining under the influence of
enhanced moisture from Post-Tropical Storm Beryl by the start of the
long term period Thursday. However, there remains two main areas of
uncertainty: timing and evolution of the system`s final stages.
Medium to long range guidance has struggled to pinpoint the
interaction between the northeast-propagation of the weakened Beryl
with a stalled, mid/upper-level shortwave trough spanning a good
portion of central CONUS. The best consensus at this time yields a
solution wherein amplifying ridging over the western CONUS forces
the aforementioned, positively-tilted shortwave to begin to
slide slowly eastward. The post-tropical low, now embedded
within its leading flank becomes situated within the northeast
Ohio Valley/southeast Great Lakes region whilst a potentially
potent, southwest to northeast-reaching axis of moisture becomes
established along much of the Eastern Seaboard, pinned against
the outer reaches of the Bermuda High established in the central
Atlantic. Should this solution be realized, our region would be
encompassed within the warm sector between the system`s
northward-lifting warm front and its cold front approaching form
the southwest. This could potentially lead to a continuation of
widespread rain throughout eastern New York and western New
England with embedded moderate to locally heavy rainfall rates
especially should sufficient instability be reached within the
warm sector to generate embedded thunderstorms within the more
or less stratiform rain shield.

That said, the discrepancies in the orientation of the mid/upper
shortwave as well as timing of the northeast track of the post-
tropical low and subsequently its associated cold front contribute
considerable uncertainty in where and if additional axes of heavy
rainfall develop. According to the latest NAEFs, PWATs on Thursday
will range from 2"-2.5" (+2 STDEVs above normal) and with enhanced
convergence in the lower levels and our region falling near the
divergent right entrance region of an upper-level jet, there will
certainly be fuel to forcing for moderate to heavy rain to be
produced. But timing and evolution of these features will be crucial
in our resulting reality. At this time, the cold front looks to push
through the region more or less from southwest to northeast
throughout the day Thursday into Thursday night leading to
additional lingering showers into Friday morning. This will be
especially true for portions of the lower Mid-Hudson Valley and
western New England as the boundary looks to stall as it comes into
contact with the outer edges of the persistent high off shore.

The main impact/concern with this system is the potential for
isolated to scattered flash flooding. It is very possible,
especially if multiple batches of moderate to heavy rainfall develop
and move over repeat areas, that some instances of flash flooding
could arise. With an anticipated soaking rain of 1.5" to 2.5",
locally lower amounts closer to 1", and locally higher amounts
closer to 3" when all is said and done, ponding of water in poor
drainage and urban areas is likely regardless of flash flooding.
However, with higher amounts of rainfall expected, at this time, to
fall within portions of the Southwest Adirondacks, Mohawk Valley,
Upper-Hudson Valley, Capital District, southern Vermont, and
northern Berkshires, the Weather Prediction center has issued a
Slight Risk for Excessive rainfall in anticipation that these
amounts will lead to an increased likelihood of isolated to
scattered instances of flash flooding in these areas. It is
important to note, however, as lead time decreases and confidence
increases in regards to the discussed conditions, the Excessive
Rainfall Outlook is subject to change.

The post-tropical low, based on greatest consensus, looks to weaken
significantly as it moves farther north and east away from the
region through Friday and into Friday night. A fairly chaotic
pattern will then remain in place through the weekend as the
aforementioned shortwave begins to weaken and move out of our area
with additional embedded shortwaves within its mean flow.

&&

.AVIATION /17Z MONDAY THROUGH FRIDAY/...
Through 12z Tuesday...VFR conditions prevail across the TAF
sites this morning with previous mist/fog having dissipated with
plenty of sunshine working to burn it off. Such conditions
should prevail throughout the 12z TAF period with some
increasing clouds throughout the day. Elevated humidity
overnight could lead to some fog/mist especially at KGFL where
less cloud cover is expected. Included an MVFR TEMPO to account
for this possibility.

Winds throughout the period will be light out of the south to
southwest at sustained speeds of 3-6 kt.

Outlook...

Tuesday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Wednesday: High Operational Impact. Likely SHRA...TSRA.
Wednesday Night: High Operational Impact. Definite SHRA...TSRA.
Thursday: High Operational Impact. Likely SHRA...TSRA.
Thursday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Friday: Moderate Operational Impact. Chance of SHRA...TSRA.

&&

.HYDROLOGY...
A warm front and the remnant moisture from TC Beryl late
Tue night through Thursday will bring potential areas of heavy
rainfall. The Weather Prediction Center has highlighted much of
our region in a threat for excessive rainfall in the Marginal to
Slight Risk categories Wed and Thu, but confidence in the
timing and coverage of any potential heavy rainfall is still
uncertain.

If confidence increases, a flood watch for flash flooding may
eventually may be needed in some areas later in the week. Some
river flooding may be possible as well.

Highest probabilities for one or two inches of rainfall Wed
through Thu continue to be from the I-90 corridor northward in
the ALY HSA, but this axis of potential heavy rain could shift
still over the next day or two. Stay tuned for further updates.

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 8 PM EDT this evening for CTZ001-013.
NY...Heat Advisory until 8 PM EDT this evening for NYZ064>066.
MA...None.
VT...None.

&&

$$

SYNOPSIS...Wasula
NEAR TERM...NAS/Wasula
SHORT TERM...Wasula
LONG TERM...Gant
AVIATION...Speciale
HYDROLOGY...NAS/Wasula