Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 261629
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
1229 PM EDT Mon Jun 26 2017

.SYNOPSIS...
An upper level disturbance will move across the region today with
mainly isolated to scattered showers and thunderstorms in the
afternoon into the early evening. An upper level low and a cold
front will bring another chance of showers and thunderstorms on
Tuesday with cooler than normal temperatures. High pressure
will build in from the Mid Atlantic Region by Wednesday, but
temperatures will still run slightly below normal for late June.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 1230 PM EDT, isolated showers are beginning to develop for
areas mainly N and W of Albany, with best coverage mainly across
the western Adirondacks, with additional scattered showers and
even some isolated thunderstorms across central NY.

12Z/KBUF and KALY soundings continue to suggest SB Capes rising
into the 400-800 J/Kg this afternoon with temps reaching the
lower/mid 70s, and sfc dewpoints generally in the lower/mid
50s, with higher pockets 1000 J/kg possible in areas where
dewpoints climb/pool into the upper 50s. At the very least,
parameters suggest any isolated deeper convective elements will
be capable of locally strong wind gusts, and small hail. Will
add this wording into gridded database for this afternoon. Best
chance for stronger winds would be if any low topped cells merge
into clusters.

Forcing for this afternoon, other than the instability/cyclonic
flow aloft, will be in the form of two main embedded shortwaves
currently noted on WV satellite imagery, one near the eastern
end of Lake Erie, with another approaching the western end of
Lake Erie. Both these features should contribute to increased
forcing through the afternoon hours to increase areal coverage
of showers/isolated thunderstorms from W to E. The second
impulse will approach a bit later during this evening, and may
contribute to lingering low topped convection for at least a few
hours after sunset.

Otherwise, just some minor adjustments to the forecast through
this evening based on current data and trends. The previous AFD
has more details and is below...

An mean mid and upper long-wave trough over southeast Canada
and the eastern CONUS will continue to impact the forecast area
the next few days. A series of short-waves moving through the
upper level trough will keep a threat of isolated-scattered
thunderstorms across eastern NY and western New England today
into Tuesday.

The upper level low continues to dig and amplify upstream over
the western and central Great Lakes Region in the water vapor
imagery this morning. The low and mid-level flow will become
southwesterly over the region ahead of the next mid-level short-
wave. The skies have become clear or mostly clear this morning
with cool temps in the mid 40s to lower 50s, but clouds should
quickly increase ahead of this next short-wave moving across MI
into the eastern Great Lakes Region. This short-wave is not as
strong as yesterdays, but still with a respectable cold pool
aloft with H500 temps of -16C to -21C and steepening mid-level
lapse rates to 6.5-7C/km coupled with weak to modest instability
in the 200-800 J/kg range with slightly higher pockets up to
1000 J/kg will allow for isolated to scattered thunderstorms to
develop in the afternoon into early evening again according to
the latest GFS/NAM. The low-level moisture is a bit sparse with
sfc dewpts in the upper 40s to mid 50s, and the 0-6 km bulk
shear values do not increase to 40-50 kts over the majority of
the forecast area until the mid to late pm ahead of the short-
wave, when the diurnal heating starts to wane. PWATS will be in
the 0.7" to 1.0" range. Most of the CAMs such as the 3-km HRRR
and 3-km NAM show a few stronger cells late in the day, but
again we are not confident about any isolated severe
thunderstorms. Some small sub-severe hail /dime size or smaller/
and gusty winds will be possible with a few cells. The
instability looks limited along with the low-level moisture for
more widespread coverage and a severe threat. We have kept POPS
in the chc range in the afternoon with some likely values near
the west-central Mohawk Valley and western Adirondacks where
some lake moisture will be tapped for a little more coverage.
Less coverage in terms of the showers and thunderstorms will be
south of the Berkshires, northern Catskills, and Capital Region.

H850 temps according to the latest GEFS will be close to 1 to 2
standard deviations cooler than normal. H850 temps fall off to
+7C to +11C from northwest to southeast across the forecast area
late in the day with short-wave and sfc trough passage. High
temps will generally be in the upper 60s to mid 70s over the
valleys and across the hills. A few upper 70s are possible in
the mid-Hudson Valley. Expect upper 50s to mid 60s over the
mountains. Humidity levels will be very comfortable for late
June with southwest to west winds of 10-15 mph.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
Tonight...The short-wave lifts northeast across the forecast
area into northern and western New England. The isolated-
scattered showers and thunderstorms should diminish quickly
between 8-11 pm. The skies will become partly cloudy. Another
cool night is expected with lows in the upper 40s to mid 50s
across the forecast area. The strong upper level trough and its
associated cold pool will be quickly approaching by daybreak
TUE.

Tue-Tue night...The H500 cold pool moves over the forecast area
with H500 temps of -20C to -23C. Low and mid level heights will
fall ahead of the upper low, and the differential cyclonic
vorticity advection will kick off instability showers and
thunderstorms in the late morning into the afternoon. Mid-level
lapse rates will remain steep coupled with SBCAPE values in the
250-900 J/kg range due to sfc dewpts in the mid 40s to mid 50s.
Wet-bulb zero heights will be in the 6-8 kft AGL range. The
deep shear in the 0-6 km layer will weaken during the afternoon
to less than 40 kts north and west of the Capital Region /but
stronger south and east/. A strong mid and upper level jet axis
will remain over the region. Some small hail mainly penny size
or smaller will be possible as well as gusty winds, as the the
cold front and upper level trough axis moves across the region.
High temps will run about 5-10 degrees below normal with upper
60s to lower 70s common in the valley areas, with some mid and
upper 70s in the mid-Hudson Valley and NW CT. Upper 50s to mid
60s will be likely across the hills/mtns. The showers and
thunderstorms decrease in coverage overnight with the loss of
the diurnal heating, as lows will be in the upper 40s to lower
50s under the cool upper low. In the H850 cold advection temps
will fall back to +6C to +10C.

Wed-Wed night...The residual cold pool and a weak impulse in
the northwest flow associated with the upper low will still
focus a few showers and thunderstorms especially north and east
of the Mohawk Valley and Capital Region during the day. High
pressure will be attempting to ridge in from the Mid Atlantic
Region. This day should not be a washout, and could end mostly
dry for the southern half or two thirds of the fcst area. High
temps will still run about 5 degrees or so below normal for late
June. Weak low and mid level ridging continues to be over the
region Wed night, but a warm front and a possible MCS may
approach from the Great Lakes Region for THU. Lows will be
mainly in the 50s with increasing mid and high clouds towards
daybreak.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
After a stretch with cool temperatures and low humidity levels, the
long term period will feature rising temperatures and humidity along
with chances for showers and thunderstorms each day.

A cyclone is forecast to track eastward across the upper Great Lakes
on Thursday. A warm front associated with this system should move
across our area, bringing showers and some thunderstorms. The best
likelihood looks to be from around I-90 northward, but at least
scattered coverage expected even farther south. Much of the
instability will be elevated on Thursday, so stronger storms are not
anticipated. Humidity will noticeably increase by late in the day,
with late day high temperatures getting back to near normal.

Models still indicating potential for showers and a few storms
Thursday evening, but coverage should decrease by around late
evening. Thursday night will be the first of a string of warm/muggy
nights through the upcoming weekend, with low temps mainly in the
60s.

Despite the lack of any significant cyclones and/or boundaries
around on Friday, there could still be scattered showers and
thunderstorms around due to zonal flow aloft with embedded
disturbances moving through. With warm temps and dewpoints in the
mid to upper 60s, it will not take much heating/forcing to produce
diurnally driven scattered convection.

Saturday looks to be a potentially active convective day and will
have to be watched for strong to severe thunderstorms. A cyclone is
forecast to track near or north of the St. Lawrence river valley,
with a pre-frontal trough moving through our area during peak
heating time. Moderate to high instability may develop given
sufficient heating. It will remain humid, so gusty winds and locally
heavy rainfall could occur with any storms.

Depending on the eventual timing, the actual cold front associated
with the Quebec cyclone may result in additional showers and
thunderstorms on Sunday.

While there is at least a chance of showers and/or thunderstorms in
virtually each period of the long term forecast, it will not be
raining the entire time. However, it should be stressed that anyone
with outdoor plans should stay informed and be alert for the
potential for thunderstorms.

&&

.AVIATION /16Z MONDAY THROUGH FRIDAY/...
Tranquil conditions this morning with mid level clouds gradually
developing. Then scattered showers and thunderstorms are
expected to develop this afternoon as an upper level trough
approaches from the west, mainly affecting the KGFL/KALB/KPSF
terminals. Will mention VCSH and PROB30 groups spanning early
afternoon into the evening to account for possible multiple
rounds of scattered convective showers/T-storms. Brief gusty
winds and MVFR/IFR conditions will be possible with any
showers/storms.

Showers and thunderstorm should end by midnight, with dry
conditions overnight. There is a chance for some fog
development at KGFL/KPSF if skies sufficiently clear and rain
occurs today. Not enough confidence to mention in TAFs just yet.

Winds will be west-southwest around 5 kt or less through much of
the morning, increasing to around 5-10 kt by this afternoon.

Outlook...

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

&&

.FIRE WEATHER...
An upper level disturbance will move across the region today with
mainly isolated to scattered showers and thunderstorms in the
afternoon into the early evening. An upper level low and a cold
front will bring another chance of showers and thunderstorms on
Tuesday with cooler than normal temperatures. High pressure may
bring dry weather from the Capital Region south on Wednesday.

The RH values will lower to 35 to 65 percent across the region
today with the lower values across the Mid-Hudson Valley and
northwest Connecticut. Expect a near full recovery in the RH
values Tuesday morning in the 85 to 100 percent range and the
minimum RH values in the afternoon will be in the 35 to 60
percent range.

The winds will from the southwest to west at 5 to 15 mph today,
and 5 to 10 mph tonight. The winds will increase from the
southwest to northwest at 10 to 15 mph Tuesday with some gusts
in the 20 to 25 mph range.

&&

.HYDROLOGY...
No widespread hydrological problems are anticipated over the
next several days. Scattered showers and isolated to scattered
thunderstorms are expected today through Tuesday, mainly during
the afternoon and evening hours, as a series of disturbances
impact the region with an upper low. Basin average rainfall
amounts will generally be a tenth to a quarter of an inch in
some locations.

A brief period of mainly dry weather is expected most of
Wednesday into Wednesday night with ridging from the south. An
active pattern sets up Thursday into the weekend with showers
and thunderstorms possible with increasing humidity levels.
Rainfall amounts will vary based on where any convection
occurs. The most widespread potential rainfall is expected
Thursday and Saturday.

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...Wasula
NEAR TERM...KL/NAS/Wasula
SHORT TERM...Wasula
LONG TERM...JPV
AVIATION...JPV
FIRE WEATHER...Wasula
HYDROLOGY...BGM/Wasula



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