Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 200601
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
201 AM EDT Sun Aug 20 2017

.SYNOPSIS...
An upper level trough will bing a threat of isolated showers and
thunderstorms early tonight. 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 warm weather Monday into Tuesday.

&&

.NEAR TERM /THROUGH TODAY/...
Showers are exiting eastern NY and decreasing in coverage.
Mesoscale models suggest isolated showers could linger until
daybreak in the western Mohawk Valley. There could still be
some patchy fog development where some breaks in the clouds
through daybreak. Just minor adjustments to rain chances and
temperatures through daybreak based on current data and trends.
Lows in the lower to mid 60s but some upper 50s southern
Adirondacks.

&&

.SHORT TERM /TONIGHT 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 /06Z SUNDAY THROUGH THURSDAY/...
An upper level trough continues to move across eastern NY and
western New England this morning. Some isolated showers and
sprinkles will end early this morning. High pressure will ridge
in from the Ohio Valley and Mid Atlantic Region today into
tonight.

Some isolated showers and sprinkles continue with the upper low
moving across the region. VCSH groups were kept in a few more
hours at KGFL/KALB/KPSF. Mid and high clouds are mainly over the
TAF sites, but some noted clearing west of the Hudson River
Valley into central NY is allowing for some patchy mist/fog and
low stratus to form. Not much rainfall has fallen, but upstream
observations model soundings support some MVFR stratus
developing over KGFL/KALB/KPSF. We placed some cigs in the
1.5-2.0 kft AGL range at these sites with a TEMPO from 09Z-12Z for
possibly IFR cigs at KALB due to the spotty light rain showers.
KPSF may have a brief period of some patchy IFR mist and a
TEMPO was used to address that in the same time frame. KPOU
should remain VFR with some high clouds lingering.

In the wake of the upper low and a weak sfc trough, the winds
will begin to increase towards 12Z-14Z and the lingering low
stratus should quickly dissipate. The MVFR stratus may persist
the longest at KPSF. By the late morning into the afternoon
expect sct-bkn diurnal fair weather cumulus in the 4-5 kft AGL
range. The skies will quickly clear in the late afternoon.

The winds initially will be variable in direction at 5 kts or
less, then increase from the west to northwest at 8-12 kts in
the late morning into the afternoon with some gusts in the 15-20
kt range 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...NAS
SHORT TERM...SND
LONG TERM...Thompson
AVIATION...Wasula
FIRE WEATHER...SND
HYDROLOGY...SND
EQUIPMENT...



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