340
FXUS61 KALY 061828
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
228 PM EDT Thu Jun 6 2024

.SYNOPSIS...
Humid today with morning clouds breaking for some sun this
afternoon as showers and thunderstorms track from west to east
through early evening. Any thunderstorm can produce heavy
downpours. Temperatures and humidity trend downwards with
unsettled conditions tomorrow through the weekend, with a chance
for showers and a few rumbles of thunder each afternoon and
evening.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1:40pm EDT, a warm and very humid day continues today
with temperatures reaching around 80 in the Hudson Valley and
mid to upper 70s elsewhere thanks to some limited breaks of sun
and thinning of cloud coverage (cooler upper 60s in the high
terrain). Convection out ahead of the abrupt wind shift boundary
in Central NY is spilling eastward into the Mohawk Valley and
northern Catskills early this afternoon. Also, our warm front
near the I-84 corridor is lifting northward as seen via sfc
observations with winds shifting to the south in the mid-Hudson
Valley. The true warm sector is located well to our south and
with only limited sun so far, ML CAPE and SB CAPE remain low
ranging just 500 - 1000 J/kg despite the moisture rich
environment. Given this and the strong low and mid-level jet
being located within the warm sector over the mid-Atlantic, SPC
maintains a "marginal risk" for severe weather today and
upgraded the mid-Atlantic to a slight risk. Still expecting an
area of rain and thunderstorms to increase in coverage and
spread across eastern NY and into western New England this
afternoon through early evening (2 - 10pm) with the P.M commute
likely featuring periods of rain and rumbles for much of the Hudson
Valley. Will maintain a watchful eye on storm intensification
as the wind shift boundary pushes eastward but with it moving
into an environment with weak instability and deep layer shear
values only topping out around 30kts, we do not expect
widespread severe weather. Still, heavy downpours/high rainfall
rates thanks to efficient warm rain processes and very moisture
rich environment may result in poor drainage flooding.

Most of the rain should be east of the region by 10-11pm. Winds
sharply shift to the west in the wake of the wind shift boundary
and should briefly become breezy with gusts up to 20kts
possible. Clouds quickly clear in the wake of the boundary
late this afternoon into the evening from west to east with dew
points dropping as dry air quickly ushers into the region.
Humidity levels drop with dew points and temperatures remaining in
the 50s to around 60. Patchy fog may develop given the clearing
clouds and afternoon rainfall but with drier air moving into
the region, only expecting patchy coverage.

Previous discussion...Our morning 12 UTC ALY sounding show a
very moisture rich and tall/skinny CAPE profile including PWATs
near 1.80" which is nearly 2.5 standard deviations above normal
per the NAEFS. Also our freezing level is quite high at around
13kft. This environment will support efficient warm rain
processes and potential for heavy downpours. Otherwise, a sfc
warm front remain positioned to our south around the I-84
corridor with east-northeasterly winds along the interstate and
southwesterly and even westerly winds to the south in NJ.

While we should have break for mainly dry conditions through
17 UTC or so, a sharp wind shift boundary currently in western
NY is quickly tracking eastward. Water vapor imagery in
western/central NY shows a weak MCV signature along the
boundary likely where a weak sfc low is developing along the
triple point where the warm front, cold front, and occluded
boundary meet. As this boundary and sfc low push eastward, an
area of showers and thunderstorm will increase in coverage.
While we have widespread cloud coverage in place this morning,
any breaks of sun will easily contribute to increased
instability thanks to high dew points in the 60s. Just how much
sun occurs remains uncertain but high res guidance continues to
indicate at least some breaks of sun should occur ahead of the
wind shift boundary/triple point. The HREF and other CAMs
suggest up to 1000 - 1500 J/kg of SB CAPE will develop ahead of
the boundary thanks to breaks of sun with the best chance for
breaks of sun mainly along and west of the Hudson River. While
shear this morning remain paltry, as the boundary approaches,
the kinematics should increase with 0-6km shear reaching around
30kts while 0-3km shear is limited to just 20-25kts. While low-
level speed shear is weak with the stronger winds in the higher
levels of the boundary layer, it is worth noting that the
directional shear in the lowest levels is quite impressive as
southeasterly winds abruptly shift to west- southwest behind the
boundary late this afternoon into the early evening. This will
provide strong low- level forcing to enhance lift/ascent for
rain and embedded thunderstorms to develop.

While thunderstorms will likely develop along the incoming wind
shift boundary, the main question is whether or not they will
become severe. Overall, instability and shear are rather weak
and so are mid-level lapse rates which are around 5.5C/km but
with a wedge of dry air in the wake of the incoming boundary,
DCAPE values get a little interesting increasing to 500J/kg
which could support damaging winds. However, the coverage of
these higher DCAPE values look limited so overall confidence for
severe weather is low. But, the impressive wind shift boundary
and low-level forcing still makes us uneasy and we will maintain
a close watch on radar trends through the afternoon and evening
(3pm - 9pm) when the wind shift boundary swings through the
region. Agree with the Marginal Risk from SPC given the
environment parameters in place. Should we see more breaks of
sun through early afternoon, there will be an increased risk for
severe weather and we will collaborate with SPC and neighboring
WFOs to evaluate if the convective outlook should be adjusted.

The very moist environment today will also support heavy
downpours from any storms as well. Storms should not train over
a given area and should be progressive so not expecting
widespread flooding. However, poor drainage flooding is
certainly possible for quick heavy downpours producing a 0.50 -
1 inch of rain in a short period of time from the efficient warm
rain processes.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...

For Friday, our closed low finally pushes eastward towards
Eastern NY with the leading edge of the cold pool pushing into
the area by 15 UTC or so. Morning sun will fade behind
increasing clouds as the mid-level moisture spills overhead.
Scattered showers develop along the leading edge of the
intruding cold pool and mid-level moisture by 15 - 18 UTC for
areas mainly north and west of the Capital District. Forecast
soundings show we will have a very shallow boundary layer under
the cold pool with equilibrium levels only around 15kft or so.
This will shrink our CAPE potential and lead to very shallow
low-level convection. Thus, we do expect any severe weather but
a few lightning strikes are likely as up to around 500 J/kg of
CAPE develop. Some small hail is also not ruled out as wet-bulb
zero heights drop under 10kft. Winds shift to the northwest
behind the leading edge of the cold in the afternoon leading to
slightly breezy conditions as wind becomes sustained 10-15kts
and gusts up to 20-25kts.

Scattered showers and possible storms spread south and east of
Albany by 21 UTC and expand into western New England. Given the
delayed onset of showers/storms, temperatures here will have a
better chance of reaching into the low 80s. With dew points
only in the 50s, it will feel much less humid as well. Areas
north/west of the Capital District should be cooler only
reaching into the low to mid 70s with 60s in the southern
Adirondacks.

Previous discussion...So, with some peeks of sun potentially
each morning before convective clouds form, producing a mostly
cloudy to cloudy sky, temperatures will reach the 70s to near 80
Friday and around 70 to mid 70s Saturday, with some 60s higher
terrain.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
We remain under the influence of the upper-low through the beginning
of the work week before high pressure builds in from the west
and forces the return to dry, warm weather...

By the start of the long term forecast period, the upper-low will be
located overhead, sprawled across the Ontario/Quebec border. Broad
cyclonic flow will help to maintain a relatively moist airmass,
leading to persistent clouds and additional rounds of showers and
possibly some embedded rumbles of thunder Sunday and Monday as a
weak wind shift boundary pushes through the region. Shower and
thunderstorm activity looks to be relatively scattered in nature and
will likely remain primarily diurnally driven with daytime heating
will aid in increased instability.

By Monday night, the upper-low looks to finally make its exit from
our overhead as it continues to weaken and push further north and
east. Guidance shows there could be an additional round of showers
and possible embedded rumbles of thunder Tuesday afternoon as upper
troughing looks to break away from the main low pressure core and
linger across the Northeast but these would once again be relatively
scattered and light in nature. The upper trough then looks to be
forced eastward as upper-level heights increase in response to a
mid/upper-level ridge building in across the region from the
west. With surface high pressure advancing in tandem with the
upper ridge, dry conditions will be returned to eastern New York
and western New England for Tuesday night through at least
Wednesday before a shortwave disturbance threatens to disturb
the tranquility for Thursday.

High temperatures Sunday and Monday will range primarily from the
mid/upper 60s to mid 70s with pockets of upper 50s to low 60s above
1500 ft and upper 70s in the Hudson Valley. Tuesday begins the
warming trend with temperatures increasing to the upper 60s to upper
70s before we rise back into the low 70s to low and possibly mid 80s
Wednesday and Thursday. Low temperatures throughout the period will
generally range from the upper 40s to low/mid 50s through Tuesday
night with Wednesday increasing to the low to upper 50s.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Through 12z Friday...MVFR conditions prevail at all terminals
with the exception of KPSF whose ceiling has dropped to IFR
heights. Showers have not been as extensive thus far this
morning as what was previously expected, so outside of a stray
sprinkle or two, expect primarily dry conditions into this
afternoon. There is some uncertainty with ceiling heights today
as model soundings show some pockets of dry air cutting into the
lower levels later this morning. However, generally ceiling
heights should remain within MVFR thresholds with brief
improvements to VFR possible throughout this morning.

This afternoon, MVFR heights should steadily return as scattered
thunderstorms develop. PROB30 groups were added to the TAF
groups for expected convection between 21z-01z. Thunderstorms
could drop ceilings to IFR heights with MVFR visibilities.
However, IFR visibilities are also possible should a heavier
downpour cross into the terminals. Once convection ceases
shortly after sunset due to lack of daytime heating to drive
instability, conditions will gradually improve possibly back up
to VFR conditions.

Winds throughout the 12z TAF period will be light and variable
to start, then increasing to sustained speeds of 5-10 kt out of
the southeast by this afternoon. By the end of the 12z cycle,
winds will decrease to speeds of 2-5 kt at variable directions.

Outlook...

Friday Night: Low Operational Impact. NO SIG WX.
Saturday: Moderate Operational Impact. Breezy. Chance of SHRA...TSRA.
Saturday Night: Low Operational Impact. Slight Chance of SHRA...TSRA.
Sunday: Moderate Operational Impact. Chance of SHRA...TSRA.
Sunday Night: Low Operational Impact. Slight Chance of SHRA...TSRA.
Monday: Moderate Operational Impact. Chance of SHRA...TSRA.
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: Moderate Operational Impact. Chance of SHRA.

&&

.HYDROLOGY...
Showers and scattered thunderstorms are expected through
Thursday. Rainfall amounts of around 1 inch are expected with
localized amounts up to 2 inches. Some thunderstorms will
contain heavy rain and could produce localized ponding of water
on roadways, urban and small stream flooding and standing water
in low lying areas.

No flooding of main stem rivers is expected. Additional showers
and thunderstorms will occur Friday through the weekend but
less widespread and lighter, with additional amounts of perhaps
up to a half inch of rain through the weekend.

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.

&&

$$

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