-- Discussion containing changed information from previous version are highlighted. --
969
FXUS61 KALY 211104
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
704 AM EDT Fri Jun 21 2024

.SYNOPSIS...
Very warm and humid once again today with dangerous heat
mainly for the mid-Hudson Valley and Litchfield County. After
morning sun, scattered areas of rain and thunderstorms develop again
this afternoon with some stronger storms capable of producing
damaging winds and heavy downpours possible before storms diminish
this evening. Summer warmth, humidity, and afternoon showers and
storms continue this weekend with increasing confidence for strong
to severe weather on Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...

-- Changed Discussion --
** Heat Advisory in effect for the mid Hudson Valley and all of
 Litchfield County, CT through 8 PM today.

As of 645am, patches of dense fog continue early this morning in
valley areas with even the Albany Airport reporting quarter mile
visibility but we still expect fog to burn off within the next
hour. Otherwise, latest GOES16 IR imagery shows cirrus clouds
spilling in the southern Adirondacks and Upper Hudson Valley as
our cold front from the North Country slowly drifts southward.
Our SPS for the dense fog will expire at 7am and given the
strong June sun, it should burn off shortly after thereafter.

Previous discussion...Early dense fog this morning in the Upper
Hudson, Housatonic and Connecticut River Valleys will burn off
shortly after sunrise thanks to the strong June sun angle. Then,
much of eastern NY and western New England should enjoy a
fairly sunny morning which will allow temperatures to quickly
rise into the low to even mid-80s. With dew points still
elevated in the upper 60s to low 70s, it will feel very warm and
muggy.

Clouds increase in coverage midday into the afternoon thanks to
the sfc trough from yesterday lingering near or just south of
I-90 and a secondary cold front/wind shift boundary sliding
southward from the North Country into the southern Adirondacks
and Upper Hudson Valley. These two boundaries will help focus
diurnally driven convection during the peak heating hours once
again but with both boundaries rather weak and mid-level lapse
weaker compared to yesterday, there is less confidence that
updrafts will grow tall enough for storms to become severe.
Shear is still rather marginal still only around 20-30kts
(slightly stronger north of I-90) despite the Northeast
remaining within the conveyor belt of relatively faster zonal
flow along the northern periphery of our broad ridge. The high
dew points and temperatures warming into upper 80s to low 90s
will easily support more than sufficient instability ranging
1-2k J/kg so some strong storms are still possible with cool
pools and outflow boundaries helping to initiate additional
pulse type convection. CAMs also support this thinking for
overall convective evolution. Thus, the Storm Prediction
continues to carry a marginal risk for severe weather across
much of the eastern NY and western New England with damaging
winds the primary hazard. High freezing heights and high PWATs
will also support efficient warm rain processes and heavy
downpours. Weak steering flow aloft and convection developing
along linear boundaries may allow storms to train or repeatedly
impact an area which may result in some localized poor drainage
flooding as well.

While it will still be quite warm and humid today with much of
the region warming well into the mid to upper 80s with low 90s
in the mid-Hudson Valley, heat index values only look to meet
heat advisory criteria in the mid-Hudson Valley, the southern
Taconics and Litchfield County, CT which will remain in the
slightly hotter air mass just south of sfc trough. Thus, we
maintained the heat advisory here and extended it to cover all
of Litchfield County.

Diurnal convection diminishes this evening with cloud coverage
likely lingering as our boundaries continue to be overhead.
Clouds should limit overall fog formation except in more fog
prone valley areas, especially where it rains during the
daytime. Temperatures remain quite warm/muggy with lows only
drop into the upper 60s to low 70s.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
-- Changed Discussion --
** eat Advisory for the mid-Hudson Valley was extended through
 8PM Sunday.**

Saturday is somewhat of a rinse and repeat type of day with
skies partly to mostly cloudy and our lingering boundaries
providing a focus for renewed afternoon thunderstorms. However,
our boundary should actually lift northward as a warm front
providing enough forcing for ascent for renewed afternoon
thunderstorms. We placed likely POPs in areas north I-90
throughout the day with areas to the south starting off with
chance POPs before trending to likely in the afternoon. With
increased cloud coverage, temperatures look to fall slightly
lower compared to the previous few days with highs topping out
in the mid to upper 80s for much of the area except low 90s in
the mid-Hudson Valley once again. This is just a slight
difference and it will still feel very warm and humid. We
extended the heat advisory through Saturday for the mid- Hudson
Valley where heat index values still top around 95. Lower heat
index values expected elsewhere but again it will still feel
plenty warm and humid.

Deep boundary layer shear turns higher by Saturday with 0-6km
shear values reaching 25 - 35kts, especially near and north of
I-90, as the westerly zonal flow aloft becomes stronger. Thus, some
some severe storms again are possible and SPC maintains a
marginal risk for much of the area with damaging winds still
possible. CAMs show suggest overall storm coverage is less
compared to Friday likely due to the slightly weaker instability
from cloud coverage; however, the increased shear within the
still warm and humid air mass means we will have to monitor
potential for severe storms. But, any strong to severe storms
should be more isolated than previous days.

As the warm front lifts north of I-90 by late afternoon, clouds
should give way to increased sunshine/clearing skies with POPs
trending lower south of I-90. However, a region of more
organized rain and embedded storms looks to track from west to
east across southern Canada through the North Country into
northern New England within the fast zonal flow. This could clip
the southern Adirondacks, Upper Hudson Valley, and southern VT
Saturday night so maintained likely POPs here. WPC`s slight
risk in its Day 2 Excessive Rainfall Outlook brushes parts of
the southern Adirondacks and while this may be overdone, the
general idea that more organized rain and heavy downpours from
storms passing through our northern zones is valid and worth
mentioning. Elsewhere, we trend POPs to slight chance and
chance. Temperatures stay warm and muggy with lows in the upper
60s to low 70s.

Confidence is increasing that Sunday could be our next more
widespread severe weather day. The warm sector retreats back
into the Northeast with 850hPa isotherms rising back to +18C to
+20C in response to a shortwave trough amplifying upstream in
the Great Lakes. Temperatures return back to hot and humid
levels with highs rising to the low to mid 90s for much of the
Hudson Valley up to the Capital District supporting heat index
values at or above 95 degrees. We extended our heat advisories
for the mid-Hudson Valley through Sunday where confidence is
highest for dangerous heat but this may need to be extended in
future updates. Will message potential for more widespread
dangerous heat returning in valley areas in the hazardous
weather outlook for Sunday.

Increasing height falls ahead of the incoming shortwave trough
will overspread into the Northeast Sunday afternoon into the
evening and in the presence of such a hot and humid air mass,
initially discrete thunderstorms should quickly redevelop once
any initial cap erodes away. With deep layer shear values
becoming more impressive reaching 40-45 kts, the stronger,
unidirectional southwesterly flow parallel to the incoming cold
front may result in a line of strong to severe thunderstorms.
Exactly when this line of storms tracks through eastern NY and
western New England remains a bit uncertain as some guidance
indicates it arrives during the peak heating hours while others
suggest it is delayed until the evening. Should it arrive during
peak heating, thunderstorms have a higher potential to become
severe while a delayed arrival reduces the threat. Damaging
winds would be the primary hazard but heavy downpours are also
certainly possible given PWATs around 2" and warm rain processes
still ongoing. We collaborated with SPC and given the
uncertainties in timing, it was decided to only introduce a
marginal risk in the Day 3 Convective Outlook. Should confidence
in an earlier arrival time increase, the outlook may increase
categories.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
An upper trough will be approaching from the west to begin the long
term at 12z Monday, with the cold front responsible for Sunday`s
potential strong to severe weather nearby or just to the east of our
region. There remains some uncertainty with just how quickly the
cold front departs to our east. The 00z Euro not withstanding,
general trend has been for a slightly quicker frontal passage which
would result in the deeper moisture and instability shifting off to
our east Monday, thus limiting the threat for any stronger storms.
However, with the upper trough and cold pool moving overhead during
the day, we will still have scattered pop-up showers and a few
thunderstorms in the afternoon with diurnal heating. It will be
slightly cooler and less humid behind the front with highs in the
70s for the terrain to 80s for the valleys.

Monday night and Tuesday, surface high pressure builds in from the
southwest. Diurnally driven showers/storms die off after sunset, and
with ridging aloft building overhead Tuesday looks mainly dry as
well. Tuesday will be warmer with the core of the cold air aloft off
to our east. Highs will top out in the mid to upper 80s for many
valley locations, although the humidity will remain at bay with dew
points "only" in the upper 50s to low 60s.

Wednesday through Friday...The surface high slides off to our
southeast and a warm front lifts northwards through the region
Tuesday night or Wednesday. Therefore, Wednesday looks quite warm
with highs climbing back into the low 90s for some of the lower
elevation areas south of I-90. Upper troughing and a surface cold
front will approach from the west/northwest sometime in the
Wednesday afternoon through Thursday afternoon timeframe. Showers
and thunderstorms are expected with the cold frontal passage. The
timing of the front is highly uncertain this far out in time, but if
the timing of the cold front aligns with peak daytime heating then
some stronger storms would be possible. We will likely get another
shot of cooler air behind the front Thursday afternoon into Friday,
although the cool down may be short-lived with the CPC predicting
temperatures to average above normal for days 8-14.The next
system will impact the region around Wednesday with another
round of showers and thunderstorms. In addition, temps will be
fairly warm once again with humid conditions. More significant
cooling and drying is expected towards Thursday behind this
system.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
Through 12z Saturday...GFL and PSF have seen fog/mist and LIFR cigs
all night, and fog recently formed at ALB. POU remains VFR early
this morning. Expecting fog to burn off within the next couple
hours, although given how thick the fog is it may take until 13z to
fully mix out especially at GFL. Once fog mixes out, conditions
become VFR through early this afternoon with just a few passing mid
and high clouds.

This afternoon will feature scattered showers and thunderstorms.
Will include VCSH groups at all TAF sites but only include tempo
groups for thunder at POU/PSF where confidence is highest. Tried to
focus on the most likely timing for storms with the tempo groups,
but will note that thunderstorms can`t be ruled out any time from
early afternoon through around sunset. Any showers/storms could lead
to gusty winds and brief IFR vsby reductions if over one of the
terminals. Tonight, showers diminish after sunset, but once again
expecting fog/mist to form. Areas that see rain today are the most
likely to see fog tonight, and where fog forms IFR or lower
vsbys/cigs are expected.

Winds increase to around 5 kt from the northeast at ALB/GFL by mid-
morning but remain at 5 kt or less at POU and PSF through today.
Winds become light and variable tonight after sunset.

Outlook...

Saturday Night: Moderate Operational Impact. Scattered SHRA...TSRA.
Sunday: High Operational Impact. Breezy. Definite SHRA...TSRA.
Sunday Night: Moderate Operational Impact. Numerous SHRA...TSRA.
Monday: Moderate Operational Impact. Chance of SHRA...TSRA.
Monday Night: Low Operational Impact. NO SIG WX.
Tuesday: No Operational Impact. NO SIG WX.
Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: Moderate Operational Impact. Chance of SHRA...TSRA.
-- End Changed Discussion --

&&

.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 NYZ066.
     Heat Advisory until 8 PM EDT Sunday for NYZ064-065.
MA...None.
VT...None.

&&

$$

SYNOPSIS...Speciale
NEAR TERM...Speciale
SHORT TERM...Speciale
LONG TERM...Main
AVIATION...Main