Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 250855
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
455 AM EDT Tue Apr 25 2017

.SYNOPSIS...
Coastal low pressure will bring moisture into the region today, with
scattered showers this morning becoming more widespread this
afternoon and evening. Temperatures will be considerably cooler than
the past few days. The system will exit on Wednesday, but cloud
cover will linger. A dry and warm day is in store Thursday, before a
cold front brings a chance for showers and thunderstorms Thursday
night into Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 345 am, vigorous upper low evident on water vapor over
central SC with its surface reflection analyzed south of Cape
Hatteras. Deep moisture is streaming northward in advance of
these features, encountering the very dry airmass (PW=0.36
inches) noted on the 00Z KALY sounding. A band of showers is
just entering the southern tier of our CWA, tied to a leading
surge of low/midlevel theta-e. With cloud bases at KPOU down to
6.5 kft, it will likely reach the ground, albeit very lightly
given the 18F dewpoint depression. Another band of showers is
organizing over central NYS, and should push into the Western
Adirondacks prior to 12Z. A look at IR imagery and GOES-16 low-
level water vapor indicates drier air from New Jersey to the
Delmarva. As this drier midlevel air tracks across our region,
it should somewhat limit shower coverage through the early
afternoon. The exception will be the easterly slopes of the
Catskills and higher terrain of western New England, which
should see persistent upslope. Conversely, areas to the west of
the higher terrain should see some shadowing. H925 winds
increase to 30-40 kt this afternoon, so these areas can expect
gusty winds of 30-35 kt at times. A Wind Advisory is not
anticipated, but trends will be monitored should mixing be
deeper than currently anticipated. With persistent clouds and
easterly flow, high temperatures will be some 5-10 degrees below
normal.

A stronger low/midlevel theta-e surge along a 40-45kt 850 mb jet
is anticipated roughly 21Z today to 03Z Wed, which is expected
to result in a more steady period of precipitation for much of
our area. Again, the southeasterly flow will allow the terrain
to modulate the precip. The rainfall could be heavy at times
during this timeframe. Rainfall will taper off over the rest of
the night as drier midlevel air works into the region. All told,
the highest QPF of 1-1.4 inches is expected across the Catskills
and higher terrain of western New England. The Hudson Valley can
expect 0.5 to 1.0 inches (highest south), while lowest amounts
of around a third of an inch are expected over the western
Mohawk Valley.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Wednesday, the low will become stacked and slowly drift toward
around 40N/70W. While the day should be mostly dry with a weak
forcing for ascent, weak low-level winds will not allow for any
dry advection to take place, and thus a healthy amount of lower
cloud coverage should exist for much of the day. For this reason
have sided with the cooler MET MOS, which still brings highs up
toward seasonal normals. Could see some patchy fog Wednesday
night depending on whether the clouds clear. A mild night in
store with lows in the upper 40s to mid-50s.

Thursday, brief upper ridging builds in as the coastal low moves
out. The leading edge of a deep longwave trough over the western
half of the country will pivot northeastward and become
negatively tilted. A surface low will track northward across the
western Great Lakes and into southern Canada. We will be solidly
in the warm sector, but again cloud cover is a question. Large
spread in the high temperature forecast. Have again sided toward
cooler MET MOS with expected slower clearing and light surface
flow with an easterly component. Still, H85 temps approach +15C,
so overachievement potential is there, and even the cool side of
the guidance envelope is well above normal. Thursday night, the
weakening cold front with the aforementioned surface low
approaches our area. Convergence along the front appears weak,
but low-amplitude waves in fast SW upper flow should augment
ascent. Some instability is present with steep midlevel lapse
rates, so thunder is possible. Coverage will be questionable
given overall weak forcing for ascent. Lows will once again be
very mild in the 50s.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As we head into the weekend the longwave pattern will feature a
broad trough across much of the CONUS with ridging from over the
western Atlantic. While at the surface, a cold front moving across
the area should become quasi-stationary across the region as we head
into the weekend. Where the boundary settles is highly uncertainty.
Guidance is in general agreement that as we head through the weekend
energy moving in on the west coast will dig/deepen the trough over
the Plains with ridging building over the eastern United States and
western Atlantic. This will provide the region with above normal
temperatures. The resultant low pressure system that forms over the
Southern Plains is expected to track northeastward into the Great
Lakes region causing the boundary stretched across our region to
lift northward as a warm front. The placement and timing of the
movement of the boundary is very uncertain.

The threat for showers and possibly thunderstorms are expected
to linger into Friday especially for the morning as cold front
moves across the region. The forecast will remain unsettled as
we have a boundary across the region and guidance indicates many
weak short waves moving through the flow. The better chances
for showers and possibly thunderstorms are expected Monday as
the deepening low pressure system moves across the Great Lakes
region with its trailing cold front on the approach from the west.

Above normal temperatures through the period with highs mainly from
the mid 60s to upper 70s with some lower 80s for Saturday.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
A coastal low along the Carolina coast will gradually move up the
coast through the TAF period reaching the DELMARVA by 06Z/Wednesday.
The air mass in place across the region is very dry as evident by
the ALY 00Z/Monday upper air sounding. It`s taking time for the
atmosphere to moisten. Clouds will thicken and lower through the
morning with MVFR conditions expected as steady rain develops.
Conditions are expected to lower IFR by late afternoon at KPOU
and early in the evening at KALB and KSPF then persist.

Light north to northeast winds early this morning. Winds will shift
to the northeast to east and increase in speed especially across the
higher terrain of western New England where gusts into the teens
and 20s are expected.

Outlook...

Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.
Thursday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Friday: Moderate Operational Impact. Chance of SHRA...TSRA.
Friday Night: Moderate Operational Impact. Chance of SHRA.
Saturday: Moderate Operational Impact. Chance of SHRA...TSRA.
Saturday Night: Moderate Operational Impact. Chance of SHRA.
Sunday: Moderate Operational Impact. Chance of SHRA...TSRA.

&&

.FIRE WEATHER...
Rain showers will increase in coverage during the morning and
afternoon today, becoming widespread by the evening. A cool and
moist airmass will be in place today. Though Wednesday will be
nearly 10 degrees warmer, a few showers and plenty of clouds
will linger. RH values will only fall into the 60 to 80 percent
range with light winds. It will become warmer and a bit drier on
Thursday with RH values falling to 50 to 60 percent. Winds will
once again be fairly light.

&&

.HYDROLOGY...
An approaching coastal low pressure system will allow isolated
to scattered rain showers this morning to become widespread by
the late afternoon and early evening, becoming locally heavy at
times. The rainfall will taper off overnight. A persistent
southeasterly flow will result in the heaviest rainfall totals
occurring along the eastern slopes of the Catskills and Greens
and the higher terrain of Western New England, where 1-1.4
inches is expected. The Hudson Valley can expect 0.5 to 1.0
inches (highest south), while lowest amounts of around a third
of an inch are expected over the western Mohawk Valley. Some
minor river rises are possible, but river flooding is not
expected at this time.

Just a few lingering light showers are expected Wednesday, with
dry weather Thursday. An approaching cold front will bring a
chance of showers and thunderstorms Thursday night and Friday.
Additional isolated to scattered showers and thunderstorms are
possible at times over the weekend.

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...Thompson
SHORT TERM...Thompson
LONG TERM...IAA
AVIATION...IAA
FIRE WEATHER...Thompson
HYDROLOGY...BGM/Thompson



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