307
FXUS61 KALY 181055
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
655 AM EDT Tue Jun 18 2024

.SYNOPSIS...
A dangerous combination of near-record heat and elevated
humidity begins today and will continue through at least
Thursday across much of the region, especially at lower
elevations. Repeated chances for isolated to scattered showers
and thunderstorms each afternoon may provide a brief break from
the heat, which will otherwise continue ahead of a cold frontal
passage late in the week. Slightly cooler but still seasonably
warm temperatures continue through the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
**Heat Advisories in effect beginning noon today across all of
 eastern New York and western New England**

.UPDATE...As of 0650 AM EDT, a convective complex which tracked
eastward over Lake Ontario overnight has moved onshore over the
Tug Hill and continued to track eastward into the southwestern
Adirondacks this morning. While CAM guidance has not captured
this feature well, convection present within the models has
consistently dissipated as it progresses eastward into terrain
through the morning. As such, have increased PoPs within the
southern Adirondacks to chance levels through noon. Occasional
lightning has persisted within the feature overnight, and
embedded thunderstorms therefore remain possible as the complex
tracks into the region. Otherwise, have nudged temperatures and
dewpoints toward regional ASOS and NYS Mesonet observations,
with the mild start presaging a hot and humid day; see previous
discussion below...

.PREV DISCUSSION [0455 AM EDT]...The heat wave begins in
earnest today as a closed upper-level high nearing 600 dam at
500 hPa builds just to the south of the region beneath anomalous
ridging. At the surface, high pressure centered off Cape Cod
will result in southerly to southwesterly flow across the
region, while model soundings support mixing up to nearly 850
hPa, where temperatures will be 18-20C. Guidance has eased
surface temperatures downward a few degrees, which seems to
better reflect the high-but-not-extreme temperatures aloft,
yielding afternoon highs today reaching the 80s in high terrain
with upper 80s to mid 90s at lower elevations. These values may
remain a few degrees below daily records at Albany and Glens
Falls, while Poughkeepsie may see the best chance to tie or
exceed its daily record temperature of 94 degrees.

Given deep mixing and the propensity for some high-res guidance
to overestimate surface dewpoints, have also maintained surface
humidity slightly lower than guidance, but still abnormally
high with dewpoints in the mid 60s to low 70s across the
region. Together, this heat and humidity will result in heat
indices of up to 95 degrees in the higher terrain of the eastern
Catskills, southern Adirondacks, and southern Greens, while
lower elevations see values of 95 to 104 degrees. As such, Heat
Advisories remain unchanged across all of eastern New York and
western New England, beginning at noon today. Conditions tonight
will remain mild and muggy, as temperatures only fall to lows
in the mid 60s to low 70s across the region.

An upper shortwave apparent on water vapor imagery rotating
about the northwestern flank of the anticyclone is expected to
reach the eastern Great Lakes by this evening. Ample heat and
humidity locally will yield some 1500-2500 J/kg of CAPE across
the region, with lift ahead of the upper shortwave sufficient to
support isolated to scattered convection, especially to the
north and west of Albany. While bulk shear remains low, only
some 10-20 kt per model soundings, the relatively high
instability may allow for storms to become fairly tall before
collapsing and potentially causing isolated instances of
damaging winds. SPC has therefore included much of the southern
Adirondacks, along with the Mohawk, Upper Hudson, and Schoharie
Valleys in a Marginal Risk for severe thunderstorms today. The
high available moisture may additionally result in a brief
heavy downpour within any thunderstorm.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
**Heat Advisories continue through 8 PM Thursday for all of
 eastern New York and western New England**

Hot and humid weather will persist as height anomalies aloft
reach their maximum on Wednesday, before slowly weakening
afterward. Temperatures may warm a few degrees compared to
Tuesday, reaching afternoon highs in the mid to upper 80s in
high terrain with 90s expected at lower elevations, challenging
daily records at climate sites. Steady dewpoints in the mid 60s
to low 70s will continue to yield potentially dangerous heat
indices across the region. The Capital District remains the most
likely area to see heat indices creep above 105 degrees, which
would necessitate an upgrade to an Excessive Heat Warning,
however at this point, it appears the Heat Advisory for heat
indices up to 104 degrees will be sufficient.

With upper ridging at its strongest on Wednesday, shower and
thunderstorm coverage will likely be at a minimum, although
isolated convection remains possible, especially across the
higher terrain of the southern Adirondacks. Any storms will
diminish into the evening following the loss of diurnal heating.
Mild and muggy conditions will persist through another night, as
temperatures again only fall to lows in the mid 60s to low 70s.

By Thursday, similarly hot and humid conditions are again
expected which may challenge daily record highs as heat indices
again reach up to 95 degrees in higher terrain and 95 to 104
degrees at lower elevations. At this point, Heat Advisories
continue through 8 PM Thursday evening. A disturbance passing
to the north may support scattered showers and thunderstorms,
potentially resulting in isolated damaging winds and brief heavy
downpours, particularly north of I-88 and I-90. Summer will
officially begin at 450 PM EDT, as temperatures are reaching
their maximum for the day. Yet another mild and muggy night is
expected as overnight lows remain stuck in the mid 60s to low 70
across the region.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
After consecutive days of hot and humid weather through much of the
work week, our strong closed anticyclone with heights near the
highest end of what both the NAEFS and GEFS have modeled starts
flattening out by Friday. This will result in zonal flow developing
across the Northeast as weak shortwaves embedded in the fast
westerly flow aloft round the top of the ridge. A weak surface
boundary from the International border also drops southward by
Friday, with sfc winds veering to the northwest as it presses
southward. All of these features should provide enough lift and
forcing for ascent to break the cap and, in the presence of rather
high instability, should easily support afternoon showers and
thunderstorms. Increased speed and directional shear will also help
support more organized convection. Continue to show widespread high
end chance POPs but held off on likely given uncertainty on exact
placement and timing of the incoming boundary. Otherwise, the
incoming boundary will also help push the hot air mass southward so
high temperatures, mainly north of I-90, should not be as
oppressive. Areas south of the Capital District will likely still be
quite hot in the mid-90s and heat advisories will likely be needed
for at least the mid-Hudson Valley. Highs only reach into the mid to
upper 80s to perhaps around 90 in the Capital District with cooler
temperatures only reaching into the upper 70s to around 80 in the
higher terrain of the southern Adirondacks and southern Greens.
Shower and thunderstorm activity diminish with the loss of daytime
heating but continue to show slight chance/low end chance POPs
overnight thanks to the front lingering overhead. Otherwise, warm
and muggy conditions continue Friday night thanks to cloudy skies.

By Saturday, weak high pressure builds behind the front over the
North Country which should help direct cooler and less humid air
into more of eastern NY and western New England. It should also help
push the boundary southward; however, just how far south the
boundary tracks remains uncertain as most guidance suggests it gets
hung up over southeastern NY. Where the boundary stalls will act as
a favored location for renewed diurnal showers and thunderstorm
activity, especially as the "ring of fire", or the periphery of the
broad anticyclone, slowly drifts southward into eastern NY and
western New England. Given ongoing uncertainty on its exact
placement, we show widespread chance POPs. Between the scattered
showers/storms, increased cloud coverage and sfc front pushing our
hot air mass southward, daytime temperatures Saturday should not be
as oppressive as previous days. Expecting highs to only top out in
the mid to upper 80s for valley areas and 70s for the high terrain.
Humidity levels should be a bit lower as well. Heat advisories
therefore appear unlikely for Saturday.

Our stalled boundary lifts northward as a warm front on Sunday in
response to a potent shortwave amplifying in southern Canada. While
the warm sector looks to return northward in response, it is unclear
exactly how warm we may get on Sunday thanks to increased cloud
coverage, shower/storm coverage, and boundary layer mixing depth
uncertainty. We therefore are only messaging highs returning to the
mid to upper 80s with dew points also creeping back upwards. When
the main sfc cold front tracks through late in the day or even
Sunday night, an organized line of shower and thunderstorms could
develop, given plenty of instability and increased shear.

Monday remains muggy and warm as we stay ahead of the incoming
parent shortwave trough Canada. Once the main trough axis swings
through during the day, renewed shower and thunderstorm activity is
likely with the true air mass change arriving Monday night into
Tuesday. While temperatures and dew points trend downwards, bringing
some relief from the heat/humidity Tuesday, we do not expect a
significant cool down. In fact, the respite looks short before broad
ridging potentially redevelops for the rest of the work week,
sending another period of warm/humid air back into the
Northeast.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Through 06z/Wed...VFR conditions will prevail at all terminals
for the majority of the upcoming TAF period. Currently mainly
clear skies will fade behind increasing cirrus clouds that will
spill overtop the broad ridging through the pre-dawn and early
A.M hours over much of the Northeast. Removed mention of fog at
GFL but will continue to closely monitor trends and amend as
needed. Cirrus clouds this morning will be followed by SCT mid-
level clouds with a few isolated showers and thunderstorms
developing in the higher terrain areas. An isolated shower or
storm may spill in the valley and impact a terminal but not
enough confidence in the the exact placement or timing of any
one shower or storm to include in the latest forecast. Instead,
only included VCSH at PSF which is higher in elevation and thus,
has a better chance of experiencing a brief shower/storm. Any
shower/storm and mid-level clouds clear out by 00 UTC.

Light and variable winds through 12 UTC except at ALB where
sustained winds remain around 5-8kts. South to southwesterly
winds increase to become sustained 5-8kts at all terminals by
14-16 UTC with gusts up to 15kts. Winds turn light and variable
after 00 UTC.

Outlook...

Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: Moderate Operational Impact. Chance of SHRA...TSRA.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: Moderate Operational Impact. Chance of SHRA...TSRA.
Friday Night: Low Operational Impact. Slight Chance of SHRA...TSRA.
Saturday: Moderate Operational Impact. Chance of SHRA...TSRA.
Saturday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Sunday: Moderate Operational Impact. Chance of SHRA...TSRA.

&&

.CLIMATE...
Record High Temperatures:

Tuesday, June 18:
Albany - 97 (1957, 2018)
Glens Falls - 95 (1907)
Poughkeepsie - 94 (2018)

Wednesday, June 19:
Albany - 94 (1995)
Glens Falls - 97 (1995)
Poughkeepsie - 92 (1941, 1943, 1993, 2016)

Thursday, June 20:
Albany - 97 (1953)
Glens Falls - 97 (1923)
Poughkeepsie - 96 (2012)

Friday, June 21:
Albany - 97 (1938)
Glens Falls - 96 (2012)
Poughkeepsie - 97 (1949)

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory from noon today to 8 PM EDT Thursday for CTZ001-
     013.
NY...Heat Advisory from noon today to 8 PM EDT Thursday for NYZ032-
     033-038>043-047>054-058>061-063>066-082>084.
MA...Heat Advisory from noon today to 8 PM EDT Thursday for MAZ001-
     025.
VT...Heat Advisory from noon today to 8 PM EDT Thursday for
     VTZ013>015.

&&

$$

SYNOPSIS...Picard
NEAR TERM...Picard
SHORT TERM...Picard
LONG TERM...Speciale
AVIATION...Speciale
CLIMATE...Rathbun