Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 192348
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
748 PM EDT Sat Aug 19 2017

.SYNOPSIS...
An upper level trough will bing a threat of isolated showers and
thunderstorms this evening, especially from the Hudson River Valley
westward. High pressure building into the mid-Atlantic region will
bring fair weather and seasonable temperatures on Sunday. A
southwesterly return flow around the high will bring mostly sunny
and hot weather Monday into Tuesday.

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...
As of 730 pm, broken line of showers/embedded thunderstorms from
Otsego County NY back into north-central PA was just about to
advance into our CWA. Leading storm appears to have a wind
signature with it, as a 38 mph gust was recorded at the Laurens
mesonet site. Still, convection is rather shallow, with SPC
mesoanalysis indicating around 500 J/kg SBCAPE. Convection
expected to mainly remain subsevere, but isolated gusty winds to
40 or 50 mph cannot be ruled out. Going forward, CAMs indicate
potential for scattered showers to advance across the CWA ahead
of a potent upper level wave. Showalter indices remain negative
with a few hundred J/kg MUCAPE, so isolated storms are possible
as well. After 06Z, the activity should have wound down or moved
east of the local area. Updated PoPs/sky grids to reflect this
thinking.

As of 426 PM EDT...radar shows a small shower over western
Montgomery County. Stronger showers are over the Finger lakes
and western New York. At this time, only lightning strikes are
with a couple of cells in far western New york. The heavier
showers and storms appear to be a couple of hours away from our
western zones.

Water vapor loop shows the upper level trough axis about between
Toledo and Cleveland, Ohio, in line with the back edge of the
storms. Models indicate this trough should be east of the Albany
Forecast area by 08Z tonight ending the threat for showers.
HRRR seems to agree that there is a threat for showers and
thunderstorms in our area through about 06z for areas west of
the Hudson river and through about 08Z for areas east of the
hudson River.

Expecting showers with isolated general thunderstorms with a
locally heavy downpour possible in a few spots.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH MONDAY NIGHT/...
Any lingering isolated showers and thunderstorms will end around
midnight to 2 AM and the sky will gradually clear. There could
be some patchy fog around daybreak Sunday. Sunday looks dry and
sunny as high pressure builds from the Ohio Valley to the mid-
Atlantic with highs in the 80s and 70s in higher terrain. Sunday
night should be mainly clear and cool under high pressure that
ridges down the eastern sea board. Lows in the 50s and 60s.

Some warm advection begins Monday as southwesterly winds
increase around high pressure near the mid Atlantic coast. Model RH
fields show generally sunny conditions for the local areas so
there should be good viewing of the eclipse. It will start to
feel hot with highs in the 80s many areas and around 80 higher
terrain. It will be interesting to see just how the eclipse does
affect the atmosphere over the entire U.S. with varying
percentages of the sun on either side of the path of the total
eclipse.

A mostly clear sky is expected Monday night with slowly
increasing warm advection and low level moisture. Lows mainly in
the 60s.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Long term period will feature a transition from summer-like warmth
and humidity to fall-like cooler temperatures and lower humidity.
This transition will occur as upper ridging Tuesday gives way to
lowering heights later Tuesday into the end of the week as an upper
trough sets up over the northeastern portion of North America. As
the lead portion of the upper trough swings in from the Great Lakes
Tuesday into Tuesday night, seasonably strong cyclogenesis is
forecast to occur over southeastern Canada. The resulting low will
drag a cold front through the forecast area, with model consensus
favoring the frontal passage Tuesday night. Convection and severe
weather can typically be expected with transitions such as this one,
but the timing of the frontal passage is not favorable for severe
weather locally. However, there is the possibility of convection
during the diurnal maximum Tuesday afternoon and evening along the
leading edge of the height falls or possibly a pre-frontal trough.
Convective potential is greatest over our northwestern zones (the
Southern Adirondacks) where likely PoPs are in place Tuesday. Chance
PoPs elsewhere. SPC Day 4 15 percent severe risk stops west of our
CWA where frontal timing is more favorable. Showers will be likely
Tuesday night, especially for the northern two-thirds of the
forecast area where forcing looks to be maximized, along with a
chance of thunder. With high temps reaching the 80s to near 90
Tuesday, and dewpoints nearing 70, it will be a hot and humid day,
but the last one through at least next weekend.

Noticeably cooler and drier Wednesday, with possibly a few lingering
showers early especially over western New England depending on
frontal timing. H850 temps fall from the neighborhood of 18C Tuesday
down to around 10C Wednesday, and down toward 8C for the remainder
of the week. The seasonably cool and dry airmass will be in place
for the remainder of the forecast period, characterized by highs in
the mid-60s to mid-70s (although a few degrees warmer than that on
Wednesday) and lows in the mid-40s to mid-50s. A couple of diurnal
showers cannot be ruled out, especially over the terrain with cold
midlevel temps and cyclonic flow, otherwise it should be mostly
dry.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Scattered showers and isolated thunderstorms are advancing into
the region this evening ahead of an upper level wave. Have
adjusted the time of VCSH for each of the terminals based on
observations/short-term model guidance. An isolated thunderstorm
cannot be ruled out during the period denoted by VCSH, but
confidence not high enough for a mention in the TAFs.

Low confidence with whether low stratus/mist will develop
tonight. Area of upstream midlevel clouds may prevent IFR
conditions, and MOS guidance keeps things VFR except for at
KPSF. On the other hand, persistence suggests it`s a good idea
to keep it in for KPSF and KGFL, as the boundary layer remains
somewhat moist. Will keep the previous forecast intact for the
overnight period.

Quick improvement for Sunday after daybreak as high pressure
noses in. VFR expected.

Winds tonight will become light and variable, increasing out of
the west to around 8-12 kt with a few gusts to near 15-20 kt
possible, especially at KALB/KPSF.

Outlook...

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

&&

.FIRE WEATHER...
An upper level trough will bing a threat of isolated showers and
thunderstorms this evening, especially from the Hudson River Valley
westward. High pressure building into the mid-Atlantic region will
bring fair weather and seasonable temperatures on Sunday. A
southwesterly return flow around the high will bring mostly sunny
and hot weather Monday into Tuesday.

RH values will be near 100 percent at night. RH values will be
45 to 65 percent Sunday and Monday afternoon.

West to northwest winds diminish to less than 15 mph tonight.
Winds will be west at 5-15 mph on Sunday with a few gusts to 20
MPH. Winds will switch to southwest and again diminish to 5-10
MPH or less on Sunday night.

&&

.HYDROLOGY...
Widespread rainfall forecast during the next week is forecast to
be less than an inch. Some locally higher amounts are possible
in showers and thunderstorms tonight and again later Tuesday
into Tuesday night. Only minor changes in stage and flow are
forecast for larger rivers and streams.

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...
While repairing the azimuthal gear box, radar technicians have
determined that the bull gear on KENX radar needs to be
replaced. This will require the radar to be out of service until
at least next Friday, August 25th.

&&

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

&&

$$
SYNOPSIS...SND
NEAR TERM...SND/Thompson
SHORT TERM...SND
LONG TERM...Thompson
AVIATION...Thompson
FIRE WEATHER...SND
HYDROLOGY...SND
EQUIPMENT...



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