Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 280154
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
954 PM EDT Wed May 27 2020

.SYNOPSIS...
A warm and humid airmass will be in place through
Friday. Isolated to scattered showers will be possible on Thursday.
On Friday into Friday night, more widespread coverage of showers
and thunderstorms are expected as a trough approaches. A cooler
and drier trend is expected for the weekend.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 945 PM EDT...00Z sounding is quite dry as high and mid
level clouds were transversing across the region from southwest
to northeast. The remnants of TS Bertha were tracking a little
more west than north into central Appalachian Mountains so the
low level wind trajectories off the Atlantic will be persistent
but light which may delay the onset of the lower stratus seen in
the GOES nighttime imagery. So the balance of the forecast will
feature variable cloud coverage (calling it mostly cloudy) and
low level dewpoints recover back toward or slightly higher than
60F. Overnight lows look in good shape and no changes at this
time.

Prev Disc, starting to get some cumulus developing due to
terrain circulations over the higher terrain surrounding the
Mohawk/Schoharie Valleys, southern Adirondacks, and western New
England. Although nothing has popped up so far, this would be
where we could get some isolated to widely scattered
thunderstorms this afternoon, as the 12Z HREF suite continues to
indicate (although CAMs appear to be having trouble resolving
ongoing convection over central/northern VT). SPC mesoanalysis
indicates 1500-2000 J/kg SBCAPE in these areas, with little to
no shear. Also, there is an absence of a trigger except for
terrain circulations. So, still not expecting organized severe
weather, although gusty winds, small hail, and downpours are
possible. Elsewhere, forecast soundings suggest capping remains
strong and lack of a trigger resulting in continuation of a dry
forecast.

Tonight, the remnants of TC Bertha are forecast to move
northwestward but remain to the southwest of our area. Deep moisture
increases late, and there are signals for onshore flow and nocturnal
cooling to allow lower stratus to expand back northward, especially
late. A mild and somewhat muggy night expected with the southerly
flow and increasing cloud cover. A couple of isolated showers or
areas of drizzle cannot be ruled out over Ulster/Dutchess toward
daybreak.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Thursday, the flow pattern will remain highly amplified with the
anomalous anticyclone centered between the Eastern Seaboard and
Bermuda, while a pair of troughs will be located over the Upper
Midwest and lower Mississippi Valley. The remnants of TC Bertha will
be assimilated into the faster midlevel flow between these features,
and will track northward well to our west. At lower levels,
southerly to southwesterly flow will prevail. But while the
anomalously warm airmass will still be located over our area, there
are a couple factors which will keep temperatures down compared with
the last two days. First, we will be in a relative minimum in
850/925 mb temps with the more anomalous warmth located to our
north. Second, there will be an increase in deep layer moisture with
PWATs increasing to greater than 1.50 inches, which will result in
increased cloud cover and decreased mixing. Still, expect a rather
humid and mild day with highs above normal in the mid-70s to low
80s. Despite the increased PWATs, there will not be much in the way
of forcing as we remain under the influence of the upper ridge. So
the PoPs will show mainly slight chances in the valleys with chance
to likely in the higher terrain. An isolated storm cannot be ruled
out mainly over the western Mohawk Valley and southern Adirondacks
where a few hundred J/kg of SBCAPE is possible. Things do not change
much Thursday night, with perhaps a few showers around and a mild
and muggy night expected.

Friday into Friday night, the upstream trough will gradually
translate eastward into the Northeast. Forecast models show the
local area basically remaining in the warm sector through the day
Friday with better low-level forcing remaining to the west. Though
midlevel lapse rates remain unimpressive, NAM12 is showing the
potential for up to 1500 J/kg of SBCAPE mainly along/west of the
Hudson, driven by a warm and moist boundary layer. Severe potential
will be hampered by the lack of forcing and weak midlevel lapse
rates, but there will be respectable deep layer shear increasing to
40+kt along/west of the Hudson from 18-24Z if updrafts can get
going. The surface front will not track through until Friday night,
so some showers/isolated storms will continue to be a threat
overnight. Very warm and muggy once again with highs in the mid-70s
to mid-80s and dewpoints approaching 70F.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
12Z Global Guidance continues to suggest a trend toward cooler and
less humid weather into the long term portion of the forecast.

We begin with this last weekend of May with the passage of a couple
of cold fronts.  The ECMWF remains the most aggressive with the cool
intrusion of air when compared to the GFS/GGEM with negative H850
temperatures.  Regardless, it will feel cooler and less humid along
with the threat for some showers as cyclonic flow aloft will bring
about a little wet weather...mainly across the terrain.

Heading into next week beginning with Monday, the last in a series
of cold fronts and upper level disturbances are scheduled to move
through where some additional showers may impact the region.  This
will keep temperatures on the cooler side under variable cloud
coverage.

Tuesday offers a variety of solutions with the ECMWF suggesting an
upstream MCS approaching the region with the GGEM/GFS much slower
and further upstream with mainly dry conditions.  This will be
dependent on the evolution of the upper low across the western
Atlantic and the amplification of the ridge axis upstream across the
Rockies and upper Plains States.  For now, we will retain slight
chance PoPs and keep temperatures below normal for early June.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
VFR conditions into the evening hours as canopy of high and mid
level clouds advect in across the region. A southerly wind
around 10kts will diminish a bit as well. Overnight, changes
from VFR to MVFR can be anticipated for all terminals as a deck
of marine layer clouds aided by southerly winds move into the
region.

As clouds thicken during the morning hours on Thursday,
precipitation probabilities will be on the increase from south
to north. Ceilings are expected to fall into the IFR category
for KPOU around 13z with all other terminals holding in the MVFR
range. Have included prob30`s for some light rain showers in
the TAFs around noontime for all the terminals and through the
afternoon hours. Any rain shower would decrease visibilities
down into IFR. The best chance for precipitation looks to come
past the TAF period or past noontime Thursday.

Winds will generally range between 5 and 10 knots out of the
south during Thursday with a few higher gusts.

Outlook...

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

&&

.FIRE WEATHER...
A warm and humid airmass will be in place for Thursday and
Friday with minimum RH values only falling to 50 to 65 percent
during the afternoon, and rebounding to 90 to 100 percent at
night. Isolated to scattered showers will be around Thursday,
becoming more widespread on Friday. Winds will be moderate from
the south. A drying trend looks to occur for the weekend.

&&

.HYDROLOGY...
Isolated to scattered showers are possible Thursday with
hydrologically insignificant QPF. On Friday into Friday night,
a warm and humid airmass will interact with an approaching
trough to generate showers and thunderstorms. Locally heavy
downpours can be expected, but widespread hydrological issues
are not anticipated. Long-term conditions remain dry, with
portions of Herkimer and Hamilton Counties in abnormally dry
conditions (D0) per latest Drought Monitor. Basin average QPF of
0.50 to 1.00 inches here may help conditions. Elsewhere, basin
average totals of 0.50 inches or less are expected.

For details on specific area rivers and lakes, including observed
and forecast river stages and lake elevations, please visit the
Advanced Hydrologic Prediction Service /AHPS/ graphs on our
website.

&&

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

&&

$$
SYNOPSIS...Thompson
NEAR TERM...BGM/Thompson
SHORT TERM...Thompson
LONG TERM...BGM
AVIATION...Evbuoma/BGM
FIRE WEATHER...Thompson
HYDROLOGY...Thompson



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