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000
FXUS61 KALY 220119
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
919 PM EDT Mon Oct 21 2019

.SYNOPSIS...
Mostly cloudy skies are expected Tuesday with temperatures near
normal. A period of rainfall expected from the late afternoon
into the overnight hours. Mainly dry and seasonable weather will
return for Wednesday. It will become milder on Thursday.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
As of 915 PM EDT, mainly clear skies and light to calm winds
continue across the region. Some patchy fog has already formed
per recent obs and also latest IR satellite imagery across the
upper Hudson Valley in portions of southeast Saratoga/southern
Washington Counties.

Expect patchy fog to continue developing overnight, with
potential for most dense and persistent fog across the upper
Hudson River Valley.

Temps have already dropped into the upper 30s to lower 40s
across portions of the southern Adirondacks, Mohawk Valley and
upper Hudson River Valley, and have therefore lowered forecast
min temps in these areas. Low temps in many areas may tend to
occur around or shortly after midnight, before possibly holding
steady or even rising as clouds, patchy fog, and/or a light
southeast wind develops depending on location.

Otherwise, all else on track, and previous discussion
follows...

As of 350 pm, stratus has finally dissipated, with clear skies
across the area. Tonight, the upper ridge axis and surface
ridge will shift east of the forecast area with heights
gradually lowering late. This is in response to a deep but
vertically stacked upper low drifting across the Upper Midwest.
Clouds will increase gradually ahead of this system, with
easterly flow increasing as well especially for the Mohawk
Valley and areas along and in the immediate lee of the
Greens/Berkshires/Taconics. Before this happens, it appears
there is a window for some fog development in the Hudson Valley,
especially given the fact that the boundary layer moisture may
not have mixed out due to today`s low clouds. Lows will likely
be a bit milder than normal given the increasing clouds, with
temps steadying and possibly rising late.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Vertically stacked cyclone will continue to drift northward
Tuesday into Tuesday night. The low-level jet will increase in
magnitude through the day, with H850 winds peaking at 35-45kt
from the south from 00-06Z Wednesday. These winds will be almost
due south, with the V-component +2 to +3 standard deviations.
This will usher in an anomalously moist airmass with PWAT
increasing to 1.25 to 1.50 inches, also +2 to +3 standard
deviations. These winds will largely be parallel to the
isentropes, and DCVA will not increase until after 00Z Wednesday
when a shortwave trough will pivot through the area. The
forecast area will also be on the equatorward exit region of the
upper jet which is unfavorable for ascent. The upshot of all of
this is that much if not all of the daylight hours will be dry
Tuesday (except for possibly some light showers/drizzle over the
eastern slopes of the higher elevations), and the rainfall will
have to wait until the forcing associated with the shortwave
trough and occluded front tracks through. It looks to be
overcast for most if not all of the day, with high temperatures
topping out near normal.

The main bout of forcing for ascent tracks through 00-09Z
Wednesday. A steady period of rainfall is expected given the
above parameters, but as it will be a progressive system, hydro
issues are not anticipated aside from some minor ponding where
leaves clog drains. Easterly winds look to be gusty across the
favored areas along and in the lee of the high terrain across
western New England, with gusts of 25 to 40 kt possible from 15Z
Tuesday through 06Z Wednesday.

Wednesday, midlevel flow flattens out in the wake of the
shortwave trough, allowing pressures to rise at the surface.
Good mixing is forecast, which should allow clouds to scatter
out during the morning. The exception will be to the lee of Lake
Ontario over the western Adirondacks, where surface to 850 mb
delta-Ts will near critical values, allowing for some lake
effect clouds and perhaps a few rain showers. It will be a bit
breezy, but with the mixing offsetting the cold advection, highs
should reach near normal values. Wednesday night looks to be a
tranquil period with low temps not far from normal.&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
We begin this long term with the approach of short wave trough
axis that, per this 12Z global model runs, takes most of the
moisture and upper support to the north and west of Albany.
Meanwhile, surface reflection frontal zone is forecast to slowly
slide eastward later Thursday into Thursday night. So
combination of clouds and low PoPs to the northwest of Albany
will remain in the forecast grids. The GFS is the most
aggressive with QPF overnight with the GGEM a little further
behind and the ECMWF the most dry. As main upper support was
departing, we will leave low PoPs/Wx until higher consensus can
be achieved. Temperatures from the 50s and lower half of 60s for
Thursday and overnight lows from the mid 30s to lower 40s.

Friday, many signals in the guidance with a wave developing
along an increasing baroclinic zone across the Ohio Valley and
tracking northeastward. The GGEM is further suppressed southward
which was not in alignment with the frontal placement and
ensemble members of the GFS/ECMWF. So we will continue with the
higher chance PoPs Friday into Friday evening. The other aspect
is the low level colder air where some wet snow could mix in
across the Dacks with no accumulation expected at this time.
Highs Friday mainly into the 50s with Friday night lows into the
lower 30s across the Dacks to lower 40s for the mid-Hudson
Valley.

Friday night and into the first half of the weekend, large
consensus for a ridge of high pressure to build and crest across
the region for seasonable weather for late October. Thereafter,
large discrepancies in the guidance with the GFS leading with a
drier Sunday as opposed to the ECMWF/GGEM with Texas upper low
and surface reflection approaching with clouds and the threat of
rainfall approaching later Sunday.

&&

.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
Tonight, lingering low level moisture should allow fog to
redevelop at all TAF sites. By 02z-05z, all sites should see
IFR/LIFR fog return, as only thin high clouds will be moving in
overnight and winds will remain very light. Towards sunrise, mid
and high level clouds will increase and a southerly wind will
pick up. This should allow fog to mix out, although it may lift
into a stratus deck at KPSF/KPOU, resulting in MVFR conditions
there for the day on Tuesday. Will allow KALB/KGFL to briefly
return to VFR, but a return to MVFR looks to occur during the
afternoon, as the southerly winds continue to bring more
moisture into the area.

Some spotty light rain or patchy drizzle will arrive later in
the day as a frontal boundary approaches from the west, and low
level moisture continues to increase from the south.

Winds will become southeast to south and increase to 5-10 KT by
late morning into the afternoon. There could be a few gusts up
to 20-25 KT at KALB and KPSF in the afternoon.

Outlook...

Tuesday Night: High Operational Impact. Definite RA.
Wednesday: Low Operational Impact. Breezy NO SIG WX.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.
Thursday Night: Low Operational Impact. Slight Chance of SHRA.
Friday: Moderate Operational Impact. Chance of RA.
Friday Night: Moderate Operational Impact. Chance of RA.
Saturday: Low Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
Southeasterly winds will increase Tuesday ahead of a frontal
system. Though most of the rain will hold off until the late
afternoon or evening, skies will be overcast much if not all of
the day. Minimum RH values will remain elevated at 60 to 80
percent. A widespread soaking rainfall is likely Tuesday evening
and Tuesday night. Breezy conditions and some sunshine will help
conditions dry out Wednesday. Dry weather will continue Thursday
with minimum RH values both days in the 45 to 60 percent range.

&&

.HYDROLOGY...
A period of steady rainfall is expected late Tuesday afternoon
into Tuesday night. Although anomalously strong low-level winds
will push precipitable water values to +2 to +3 standard
deviations, the system is progressive and the moist axis quickly
pushes east. Rivers will rise but are forecast to remain below
flood stage. QPF is expected to range from 0.50 inches in parts
of Litchfield County to 1.25 inches over the southern
Adirondacks. Some nuisance ponding of water is possible,
especially where leaves clog drains.

At this time, no additional hydrologically significant
precipitation is expected through the 7-day forecast period,
which should allow river levels to subside.

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...KL/Thompson
SHORT TERM...Thompson
LONG TERM...BGM
AVIATION...Frugis/KL
FIRE WEATHER...Thompson
HYDROLOGY...Thompson