Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 212252
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
652 PM EDT Mon Aug 21 2017

.SYNOPSIS...
High pressure will move further east of region tonight as the next low
pressure system approaches from the Great Lakes Region. It will be hot and
muggy on Tuesday with highs soaring into the upper 80s. Some spots
may even reach the 90 degree mark. Showers, along with the potential
for strong to severe thunderstorms are expected during the afternoon
and evening hours ahead of a strong cold front. Cooler and less
humid air will move into the region for Wednesday, with dry and cool
conditions expected for the rest of the week.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
As of 652 PM EDT...A batch of showers and thunderstorms is
slowly moving east to northeast from central NY and near KBGM
this hour. The latest 3-km HRRR and 3-km NAM has it move towards
the eastern Catskills/Mid-Hudson Valley and then weaken early
this evening. The latest 13-km RAP is a little more aggressive
and brings a few showers and thunderstorms to the Capital Region
and Berkshires. The latest SPC RAP Mesoanalysis has about
1000-1500 J/kg of MLCAPE south and west of Albany, but the shear
(less than 30 kts) and flow is weak ahead of this weak short-
wave and sfc trough. We expanded the low chc and slight chc pops
to just south of the Capital Region and to the Taconics up to
midnight. The activity should die out with the loss of the
diurnal heating.

Otherwise, it will be mainly dry through the overnight hours,
but it will stay fairly mild and muggy with temps only falling
into the mid to upper 60s.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
A strong upper level trough will be digging from south-central
Canada across the Great Lakes, bringing a surface cold front
through the Ohio Valley into New England. Ahead of this
boundary, a surface pre-frontal trough will help kick off some
showers and thunderstorms during the early afternoon hours.
These showers/storms will track eastward across our area by
later in the afternoon and through the evening hours.

Strong south-southwesterly flow will allow for another
unseasonably warm and humid day, with highs well into the 80s
and dewpoints approaching 70 degrees. Some locations might even
hit the 90 degree mark. It looks like quite a breezy day as
well as the latest GEFS indicates that the 850 mb u-component of
the wind is 2-4 standard deviations above normal. GEFS also
shows PWATS 2-3 standard deviations above normal. These warm
temperatures along with a moist environment and strong southerly
winds should allow for at least a moderate amount of
instability tomorrow afternoon/evening. The NAM12 is more
bullish with CAPE in excess of 2K but also shows dewpoints in
the lower 70s. The GFS still shows moderate CAPE around 1-1.5K
across our western zones with even higher instability west of
the forecast area. Even though there is still model
disagreement on the amount of instability, there still looks
like there will be plenty for storms to tap into. Additionally,
with strong upper level dynamics approaching, 0-6 km bulk shear
will be reaching around 40 kts, so the ingredients are coming
together for some stronger storms tomorrow afternoon/evening.
One mitigating factor will be that mid-level lapse rates will be
fairly weak (generally 6 deg/km or less), but the combo of
instability/shear should allow for some storm organization. The
main threat will be gusty winds, but with PWATs reaching around
two inches, will also have to watch for some locally heavy
downpours and isolated flash flooding as well.

The storms may linger into the first part of tomorrow night,
but should be ending from west to east as the front crosses the
area, as lows fall into the 60s.

On Wednesday, dewpoints will be falling during the day, as much
cooler and drier air moves into the area. Highs will generally
be in the 70s with a partly sunny sky. There still may be a
lingering shower due to the passing upper level trough, but most
areas should be dry. Skies should continue to clear out by
Wednesday night, as lows fall into the upper 40s to upper 50s,
as high pressure builds into the area.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The extended forecast continues to feature a mean longwave trough
over the region with high pressure building in at the sfc with
mainly fair and dry weather with temps slightly below normal for late
August.

Wed night into Thu...A broad upper level trough will be over
southeastern Canada, the Great Lakes Region, and the Northeast. The
latest GEFS has H500 heights 1 to 2 standard deviations below
normal.  Initially, some lake enhanced isolated showers tapping Lake
Ontario moisture will impact the western Adirondacks Wed night.
Variable cloudiness and cool temps are expected with H850 temps
falling back to +6C to +10C from northwest to southeast across the
forecast area. Lows will be in the mid 40s to around 50F over the
mountains, and lower to mid 50s in the valleys. A short-wave
associated with the upper level low and a sfc trough will focus some
isolated to scattered showers especially west of the Hudson River
Valley, and over the higher terrain. It will be cool and breezy with
highs in the lower to mid 70s over many of the valley locations with
a few upper 70s in the mid-Hudson Valley and NW CT, and 60s to
around 70F over the hills and mountains.

Thu night through into Sat night... A large dome of Canadian high
pressure builds in from Ontario and the western Great Lakes Region
Thu night into Fri.  The strong subsidence associated with the broad
sfc anticyclone will yield fair and dry weather to close the week
and enter the weekend.  The sfc high shifts eastward over s-cntrl
Quebec and the Northeast by Saturday night. Slightly cooler than
normal temps and comfortable humidity levels are expected. The 12Z
GEFS H850 temps are 1 to 2 standard deviations below normal. Lows
will generally be in the mid 40s to lower 50s. Highs Friday and
Saturday will be mainly in the lower to mid 70s in the valley areas,
and lower to upper 60s over the higher terrain.

Sunday into Monday...The 12Z GFS and ECMWF both show some short-wave
energy swinging around the H500 upper low over the Northeast and
southeast Canada on Sunday.  A few instability showers could pop up
over the southern Greens and the southern Adirondacks.  The low-
level moisture profiles are not impressive.  We placed a slight
chance of showers in for those locations, otherwise high pressure
builds back in from the Great Lakes Region Sunday night into Monday,
and low and mid level heights begin to rise.  Temps continue to be
slightly below normal by a few degrees late in the weekend into
early next week. Humidity levels continue to be comfortable with sfc
dewpts in the 40s to 50s.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
High pressure will bring mainly VFR conditions through this
evening. Skies will be partly cloudy with some cumulus and high
cirrus clouds moving across the region. With the surface ridge
shifting offshore today a southerly flow will develop and dew
points will be on the rise so fog is expected to develop again
overnight as winds become calm with MVFR at KALB and KPOU, and
IFR at KGFL and KPSF. Tomorrow, fog should burn off by 13Z all
TAF sites and VFR conditions are expected to return. A stray
thunderstorm may impact KGFL after 16Z tomorrow.

South to southwest winds today with some gusts to around 15kts
at KALB this afternoon. Winds will diminish late in the day
into the evening becoming light/variable to calm for the
overnight. South to southwest winds expected again on Tuesday at
10-20 kts.

Outlook...

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

&&

.FIRE WEATHER...
Most areas will see showers or thunderstorms tomorrow afternoon
and evening thanks to a cold front and strong upper level trough
passing through the area. Min RH on Tuesday will only be 50 to
65 percent with south winds at 10 to 20 mph. RH values will
recover to near 100 percent tonight and tomorrow night with some
patchy fog possible tonight.

&&

.HYDROLOGY...
Dry weather is expected through tomorrow morning across the
region. An approaching cold front will allow for showers and
thunderstorms tomorrow, mainly during the afternoon and evening
hours. Any thunderstorm will be capable of producing locally
heavy downpours and could lead to isolated flash flooding.
The locally heavy rainfall may result in minor flooding of
urban, poor drainage and low lying areas. Behind this frontal
system, mainly dry weather is expected for the rest of the week.

Basin average rainfall on Tuesday will generally be around a
half of an inch to an inch, although point totals may be
higher. This rainfall will only allow for minor rises on rivers
and streams. River and stream levels should quickly recede by
Wednesday and then remain steady for the rest of the week.

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.

&&

.EQUIPMENT...
The KENX radar will likely be down through at least Friday,
September 1st for the bull gear replacement. We are waiting for
a ROC maintenance team and parts to arrive to assist local
technicians with the repairs.

&&

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

&&

$$
SYNOPSIS...SND/JVM/Wasula
NEAR TERM...JVM/Wasula
SHORT TERM...SND/Frugis/JVM
LONG TERM...Wasula
AVIATION...SND
FIRE WEATHER...Frugis/JVM
HYDROLOGY...Frugis/JVM
EQUIPMENT...WFO ALY



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