016
FXUS61 KALY 271526
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
1126 AM EDT Mon May 27 2024

.SYNOPSIS...
A muggy day continues for Memorial Day ahead of an
approaching cold front. After a dry period through early afternoon,
chances for showers and thunderstorms increase with storms capable
of producing heavy rainfall and gusty winds. Mainly drier conditions
will return to the region by the middle of the week, with cooler
temperatures as well, although a stray shower still can`t be ruled
out.  It will be dry and seasonably cool to end the week, as high
pressure returns to the area.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 1050 AM EDT...A strengthening low pressure system reaching
~997hPa in the Great Lakes today will advance into Ontario and
Quebec this afternoon and tonight. A tight pressure gradient
ahead of it has led to strong southerly low and mid-level winds
and will maintain a strong moisture fetch up the East Coast.
Thus, dew points remain in the 60s today making it feel quite
muggy with PWATs exceeding 1.5", even approaching 2" later this
afternoon. Gusty southerly wind still expecting this afternoon
with gusts up to 30kts possible, especially in north - south
oriented valleys.

We will have a dry break through early this afternoon with even
breaks of sun showing up on the GOES16 visible satellite
imagery. Breaks of sun within the moist environment will support
increased surface-based instability with CAMs such as the HREF suggesting
up to 1000J/kg developing. The strong kinematics in place
thanks to the overall synoptic set-up has led to 0-6km shear
values ranging 40-45kts (also seen on the ALY 12 UTC sounding)
which will be more than sufficient to support organized
convection. As mentioned in the previous AFD, most of the shear
is within the lower 0-1km layer too.

A pre-frontal trough continues to march eastward through western
NY late this morning and has led to increased coverage of
showers and thunderstorms ahead of it as seen on GOES16
satellite imagery and radar mosaic. Increasing height falls,
forcing for ascent and cooler air aloft (including steepening
mid-level lapse rates) will spread eastward through the
afternoon. Latest CAMs suggest shower and thunderstorm activity
will reach our western zones including the western Mohawk
Valley, western Adirondacks, and eastern Catskill by 18 - 20
UTC (2 - 4pm) before spreading eastward into the Capital
District, mid-Hudson Valley, and Upper Hudson Valley by 20 - 22
UTC (4 - 6pm). Since we have a few hours of dry time and breaks
of sun ahead of the strong upper level forcing and sfc pre-
frontal trough, the environment should become favorable to
support thunderstorms and while overall instability is not very
impressive, in the presence of the strong shear in the low and
mid-levels, the environment will likely be favorable to support
some organized thunderstorms, especially west of the Hudson
River where there should be more insolation and thus more
instability. This explains why the slight risk (level 2 of 5)
from the Storm Prediction Center remains in the western Mohawk
Valley, eastern/northern Catskills and western Adirondacks with
just a marginal up to the Hudson River. Should more instability
develop further east, the severe weather potential could expand
eastward.

Gusty winds is the primary hazard from any severe thunderstorm
but given the high PWATs, high freezing levels >10kft, and
forecast soundings showing most of the instability within the
warm cloud layer, the environment will also support efficient
warm rain processes and thus heavy downpours. With 40-45kt winds
within the LCL-EL layer and these wind oriented close to the
orientation of the pre-frontal trough, some convection may
repeatedly impact an area so we will have to monitor for some
isolated instances of flooding. CAMs including the HREF
probabilities continue to point to the eastern Catskills for the
heaviest rainfall amounts where southerly winds abutting the
terrain could favor high rainfall rates (HREF 3-hr probabilities
for >1" of rain are around 75% late this afternoon into this
evening). Latest WPC rainfall amounts so 1.50 - 2" possible in
this region but given dry antecedent conditions, we are not
expecting widespread flooding but some localized flash flooding
cannot be ruled out. This support the WPC Excessive Rainfall
Outlook and the slight risk in the eastern Catskills. Luckily,
the strong winds aloft should keep the overall convection moving
and progressive.

Previous discussion...Model soundings shows PWATs
will surge above 1.50" and ensemble guidance suggest PWATs will
reach 1 to 3 STD above normal for this time of year. Although
showers and thunderstorms look progressive, some heavy downpours
are expected and there could be some isolated poor
drainage/urban flood issues around. A rogue flash flood can`t be
ruled out if heavy rainfall repeats over any one location,
although this looks like a low-end threat due to rapid movement
of precip and likelihood that the heaviest batch will be within
one main band ahead of the pre- frontal trough late today. WPC
suggests the greatest risk for this will be across the
Catskills, as this is where they have a Slight Risk for
Excessive Rainfall.

In addition, there is a threat with this activity for some
gusty winds. While instability will be limited (00z SPC HREF
shows MUCAPE values under 1000 J/kg), there is a lot of shear in
place. 0-6 km bulk shear values will be around 40 kts, with a
lot of this in the 0-1 km layer (about 30 kts or so). It won`t
take a tall storm to bring down some gusty winds, so downed tree
limbs are possible within any heavier convective element. SPC
has a marginal to slight risk for severe weather across western
areas for late today.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
Showers and t-storm will still be ongoing this evening and will
linger into the first part of the overnight, as the storm`s
cold front slowly makes progress from west to east across the
area. CAMs show most of the activity should be done by midnight
to 2 AM or so and the threat for the heaviest showers/thunder is
likely early, as the loss of heating should help keep storms
from staying strong. Otherwise, mostly cloudy skies will
gradually become partly to mostly clear towards daybreak
Tuesday, with temps falling into the mid 50s to mid 60s and
dewpoints starting to fall.

Although it will be a little less humid on Tuesday, temps still
look seasonably mild for most areas, with mid to upper 70s in
valley areas. As the upper level trough approaches, some
additional showers and possibly a rumble of thunder will be
possible for late in the day. Any activity on Tuesday look
fairly scattered and mainly limited to areas west and north of
the Capital Region. While sky cover will start off mainly clear
early in the day, it will become partly to mostly cloudy by
afternoon. Any precip should diminish for Tuesday night with
lows in the 50s (some 40s across the highest terrain).

Temps will be a little cooler for Wed into Wed night with the
upper level trough still overhead. Another disturbance rotating
around the main upper level trough will help initiate a few more
showers, although the best forcing looks to be passing south of
the region. Will continue to go with chance POPs on Wednesday
into Wednesday night for most areas, although any showers look
fairly brief and light. Skies will continue to be partly to
mostly cloudy and dewpoints will remain fairly low and
comfortable in the 40s and 50s. Highs will only be in the 60s to
low 70s with overnight lows mainly in the 40s to low 50s.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
An upper-level trough swinging across the region midweek will exit
eastward on Thursday, with rain showers diminishing from west to
east through the day as drier air arrives in its wake. Heights aloft
begin to rise late Thursday into Friday as high-amplitude upper
ridging builds over the region, bringing a return to dry weather
with clearing skies into the weekend.

Temperatures through the period trend upward each day, with
afternoon highs increasing from upper 50s in high terrain to low 70s
along the Hudson Valley on Thursday to upper 60s near 80 across the
region on Sunday. Overnight lows similarly trend warmer, from
widespread 40s on Thursday night to upper 40s to upper 50s on Sunday
night.

On the far side of the weekend, numerical guidance begins to show
substantial differences in the evolution of the upper ridge, leaving
some potential for rain shower chances late Sunday, although
confidence is low at this lead time.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
Through 12Z Tuesday...Mixed VFR/MVFR conditions expected to continue
through the morning with scattered showers tracking to the northeast
as a warm front lifts across the region. Rain showers may briefly
reduce vsbys to MVFR range through 14-15Z, while cigs trend slightly
upward through the morning as vertical mixing increases after
showers exit. A second, more coherent and steady band of
precipitation is expected to affect the region this afternoon as a
cold front approaches, arriving from the west after 19-21Z Mon.
Strong thunderstorms within the band may briefly result in IFR
cigs/vsbys at some point between 21-24Z Mon at ALB/GFL/POU and 22Z
Mon-01Z Tue at PSF. Some lighter rain showers may linger as late as
07-09Z Tue, with skies trending clearer late in the period.

Southeast winds of 10-20 kt gusting 20-30 kt are expected through
much of the period, until the cold front passes by 02-04Z Tue. Gusty
convective winds within thunderstorms may reach 30-35 kt. Low-level
wind shear will reach 30-40 kt in the lowest 2 kft around the time
of the cold frontal passage, from 20-21Z Mon through 02-03Z Tue.
Behind the front, winds decrease to 10 kt or less out of the south
to southwest.

Outlook...

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

&&

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

&&

$$

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