512
FXUS61 KALY 132037
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
437 PM EDT Tue Aug 13 2024

.SYNOPSIS...
Beautiful weather today with seasonable temperatures before
chances for isolated to scattered showers and thunderstorms
increase tomorrow and Thursday, especially in the higher
terrain, thanks to a disturbance in the Canadian Maritimes.
Humidity levels turn more uncomfortable Friday into the weekend
as a disturbance from the Great Lakes slowly pushes eastward.
Chances for showers and thunderstorms increase Saturday and
Sunday as the occluded boundary approaches.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Beautiful August day continues across the Northeast as a 1020hPa
anticyclone centered over the Great Lakes builds eastward. Morning
sun will continue to mix with some fair weather cumulus clouds
as areas reach their respective convective temperature. 12 UTC
ALY sounding shows low PWATs under 1 inch once again thanks to
northerly flow through the column as we remain on the east side
of the incoming high. Thus, humidity levels will once again be
low/comfortable today. Forecast soundings support deep boundary
layer mixing extending up to and even above 5kft this afternoon
and with 850hPa isotherms ranging from +11C to +13C, high
temperatures this afternoon should easily reach the mid to upper
70s with even around 80 in the valley.

Cumulus clouds dissipate late this afternoon once we cool below
the convective temperature. Sfc high pressure building eastward
will support ideal radiational cooling tonight thanks to clear
skies, light winds, and low humidity. Another great night to
open up the windows as temperatures cool into the mid to upper
50s across eastern NY and western New England with even mid to
upper 40s in the southern Adirondacks, southern Greens, and
higher peaks of the eastern Catskills.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
An upper level disturbance from the Canadian Maritimes will
shift into the Gulf of Maine Wednesday into Thursday as a subtle
backdoor front gradually progresses south and westward through
northern New England. Meanwhile, upper level ridging from the
Great Lakes and sfc high pressure will be slowly building into
the Northeast. Such a synoptic set-up will maintain northwest
flow over the region and keep dew points comfortable in the
upper 50s to around 60 with temperatures trending a bit warmer
rising into upper 70s to low 80s but remaining seasonable.

As the cold pool from the disturbance in the Canadian Maritimes
shifts south and westward, lapse rates will steepen over much of
eastern NY and western New England both days ranging 5.5C/km to
6C/km. After morning fog burns off, morning insolation will
contribute to increased surface based instability but marginal
dew points will keep CAPE values in check only rising to 500 -
1000J/kg. Deep layer shear values will also be minimal both days
only reaching 15 - 25kts. Thus, expecting cumulus clouds to
develop once we reach the convective temperature mid to late
morning with isolated to scattered showers and thunderstorms
developing early to mid afternoon, initially in the southern
Adirondacks and southern Greens before northerly flow directs
showers/storms southward. Any shower/storm should be short-lived
but some areas could see more than one brief shower/storm,
especially in the Mohawk Valley and Upper Hudson Valley as
shower/storms track southward out of the Adirondacks. While
storms will likely not turn severe given weak shear/instability,
the cold pool aloft (500hPa isotherms cooling to -13C to -14C)
will keep wet- bulb zero heights near or slightly below 10kft so
any updrafts that can grow tall enough may be able to support
small hail.

Isolated to scattered showers/storms diminish once we loss peak
heating late afternoon into the evening with clouds clearing and
wind becoming light/variable. With dew points remaining near 60
and radiational cooling setting in, fog looks to develop both
nights, especially in valley areas and where rain falls during
the day.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...

The upper level low from the Canadian Maritimes finally exits
by Friday as the upper level shortwave ridge finally tracks
overhead with our weakening 1020 hPa high building at the sfc.
This will support a dry and very pleasant end to the work week
with mostly sunny skies and temperatures warming into the low to
mid 80s across the region. Dew points will be on the rise as
southerly flow ensues making it feel more humid.

Clouds increase overnight as a closed/mature upper level
disturbance from the Great Lakes slowly tracks eastward.
Shortwave ridging remains in place most of Friday night keeping
conditions dry but will gradually exit into New England by
Saturday. Heights slowly fall through the day Saturday with
southerly flow ahead of the incoming warm front keeping
humidity levels high/uncomfortable. Continued warm air and
moisture advection will keep skies partly to mostly cloudy which
will keep temperatures lower compared to Friday in the mid to
upper 70s. Guidance has slowed down the eastward progression of
the upper level low which has thus slowed down the onset of the
best forcing for ascent. We thus delayed the west to east onset
of likely POPs for showers and thunderstorms until Saturday
afternoon, especially for areas west of the Hudson River. Areas
in western New England should have a better chance of staying
dry longer into the day as the upper level ridge looks to
maintain control into the first half of Saturday so we capped
POPs at chance. Given cloud coverage, instability may be limited
as well despite the high humidity so there is low confidence in
storms becoming severe. High humidity and PWATs rising above
1.50" means heavy downpours are possible from any storm.

The occluded boundary/triple boundary look to track into the
region on Sunday with the parent closed low remaining upstream
in southern Ontario or western NY. Continued height falls and
increased sfc convergence along the incoming boundary keeps
POPs in play for Sunday and we show widespread chance POPs
Sunday morning trending to likely during the afternoon diurnal
peak heating times. High humidity levels and PWATs >1.50" means
heavy downpours will once again be possible. Again, cloud
coverage will temper temperatures albeit very uncomfortable
humidity levels so highs only expected to rise into the mid to
upper 70s to perhaps around 80 in the valley.

Guidance suggests our upper level low opens up by Monday but
remains nearby as trough axis tracks into the Northeast so we
continue to show chance POPS trending to likely by the afternoon
throughout the area. Temperatures again remain seasonable in the
upper 70s to around 80 with high humidity continuing.

We should finally trend drier by Tuesday as our upper level
lows should exit but there remains some differences among the
guidance on when drier conditions ensue.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
Flying conditions are currently VFR across the region with just some
diurnal cumulus and some passing thin high cirrus clouds.  Through
the rest of the day, flying conditions will be VFR with light north
to northwest winds.

Skies will clear out for tonight with very light or calm winds. This
could allow for some radiational fog to develop for the late night
hours at KGFL and KPSF, but the other sites should have a large
enough T/TD spread to prevent any fog from developing.

On Wednesday, any early morning fog or mist will dissipate shortly
after daybreak.  This will allow for another day of VFR conditions
with just few-sct clouds for the morning and early afternoon hours
around 4-6 kft.  North to northwest winds on Wednesday will be
around 5 kts for all sites.  A stray shower or t-storm cannot be
ruled out for the mid afternoon into early evening hours, mainly for
the northern sites.

Outlook...

Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: Moderate Operational Impact. Scattered SHRA...TSRA.
Thursday Night: No Operational Impact. Patchy FG.
Friday: No Operational Impact. NO SIG WX.
Friday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Saturday: Moderate Operational Impact. Likely SHRA...TSRA.
Saturday Night: Moderate Operational Impact. Likely SHRA...TSRA.
Sunday: High Operational Impact. Likely SHRA...TSRA.

&&

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

&&

$$

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