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FXUS61 KALY 240220
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
1020 PM EDT Tue Oct 23 2018

.SYNOPSIS...
An upper level low pressure area will track east across the
area bringing a few showers tonight. Scattered rain and snow
showers will persist over higher elevations into Wednesday as
surface low pressure deepens east of New England. Dry and
unseasonably cold weather is expected for much of the region
from Wednesday into Friday as high pressure builds in from
eastern Canada.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
Update as of 1020 PM EDT, rain showers have diminished some
over the past 3 hours, but continue over parts of the southern
Adirondacks, northeastern Catskills, Lake George Area, northern
Taconics, northern Berkshires and southern Vermont. This trend
of diminishing coverage should continue overnight as the upper
level low and cold pool slowly move eastward. Winds have become
west to northwest across the area and temperatures range from
the mid 30s in the southern Adirondacks and higher terrain of
southern Vermont to the 40s elsewhere. Based on higher elevation
station temperatures and KENX melting layer, the snow line is
probably down to 3000 FT MSL.

Previous,
The coverage of showers will be much less on Wednesday mainly
confined to the northern half of the forecast area. It will be
cold enough such that some of the showers especially across the
northern mountains will be in the form of snow. However, due to
very little moisture in place with the upper trough any
accumulation will be minimal, generally an inch or less with the
greatest accumulations across the western Adirondacks and the
high terrain of the southern Green Mountains. Expect Wednesday
to be a windy day as a strong pressure gradient will be across
the area between the departing surface low and high pressure in
the Great Lakes region. Wind gusts may top 35 mph at times. Lows
tonight will be in the upper 20s to lower 40s with highs on
Wednesday in the mid 30s to around 50.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Wednesday night and Thursday are expected to be mainly dry with the
exception of a few rain or snow showers across the northern portions
of the western Adirondacks Wednesday night. It will continue to be
chilly with lows Wednesday night in the mid 20s to mid 30s and highs
on Thursday in the upper 20s to mid 40s.

Dry weather is expected to continue Thursday night through Friday as
a ridge of high pressure will be centered across the region Friday
morning before lifting northward Friday afternoon. While Friday will
be dry, clouds will increase mainly during the afternoon as Low
pressure lifts northward from the southeast coast. Lows Thursday
night will be in the 20s to lower 30s with highs on Friday in the
upper 30s to upper 40s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The main focus of the long term period will be on the
potential coastal storm this weekend, as discussed in previous AFDs.

The period begins on 00z Saturday with a large scale 1030mb high
pressure nosing into northern New England with 850mb temperatures
ranging 0C to -5C across eastern NY/western New England. There is
fairly good agreement among the global guidance that our developing
coastal storm looks to be off the coast of the Carolinas and moving
northward (side note...this storm may have some remnant moisture of
Hurricane Willa currently impacting Mexico). Clouds should be
increasing from south to north Friday night as 700mb flow becomes
southerly and warm air advection increases ahead of the approaching
coastal storm.

As we move towards 06z - 12z Saturday, the aforementioned high
pressure moves into the Gulf of Maine/Canadian Maritimes as the
center of the coastal storm advances into the mid-Atlantic. This is
where we see disagreement among the global guidance as the CMC and
ECMWF continue to be in line showing the northern edge of the
precipitation shield moving into the mid-Hudson Valley and northward
towards the Capital District while the GFS is still the slowest
solution with the precip shield still only in NJ/PA. The reason for
this discrepancy likely stems from the position of the high where
the GFS shows it anchored in Quebec which would block its northward
advancement while the CMC and ECMWF are much further east with it in
the Canadian Maritimes. For now, will continue to take a blended
approach with high chance POPs for the mid-Hudson
Valley/Catskills/NW CT for 06z-12z Saturday with low chance/slight
chance POPs for the Capital District/Berkshires/southern VT.

Of course, the big question remains of what will the precip type be
of any precip that arrives before sunrise Saturday. It's worth
noting that MOS guidance shows dew points at the start of the event
in the upper 20s to low 30s with overnight temperatures in the low -
mid 30s. Given the strong 700-500mb frontogenesis with the northern
precipitation shield, precipitation could fall steady initially
meaning evaporative cooling processes could very well be sufficient
to cool down the column. Thus, we continue the mention of snow in
the mountains/higher elevation with rain/snow mix in valley
locations for this time period. Given the marginal temperatures and
short window of opportunity for wintry precip, thinking most
accumulations should be reserved for elevations above 500-1000ft.
Will continue to monitor as heavy enough precipitation could allow
some brief coatings even in the valleys.

By daytime Saturday, strong warm air advection should occur (50kts
at 850mb) within the warm sector that the boundary layer should warm
allowing a transition back to mainly rain (expect maybe highest
peaks of Dacks/Greens). Of course this will all depend on storm
track which remain uncertain at this time.

Besides precip type issues, strong winds may also be another hazard
with this event. As mentioned earlier, 925mb and 850mb winds are
quite impressive ranging 35-50kts which could lead to strong winds
for the higher elevations. However, the height of the inversion
associated with the warm layer could impede mixing. Will need to
monitor the potential for strong winds in the coming days.

As the storm exits Saturday night, a mix back with snow could be
possible especially for the higher elevations and reflected this
thinking in the current update.

Heading into Sunday - Tuesday, unsettled weather continues as the
upper level 500mb trough looks to cut off. Continued the mention for
chance POPs for Monday and even into Tuesday as multiple shortwaves
round the large scale cut off low. Temperatures look to remain near
or slight below normal as well.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Expect a mix of MVFR and VFR conditions across the TAF sites
during the next 24 hours. Some LIFR possible at KPSF. Showers
will continue overnight but gradually diminish at the TAF sites.
Clouds will continue to linger throughout the day on Wednesday.

Winds will be westerly at 5 to 10 kts overnight. On Wednesday
winds will increase out of the northwest at 10-15kts with gusts
up to 25kts possible.

Outlook...

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: Moderate Operational Impact. Chance of RA...SN.
Saturday: Moderate Operational Impact. Chance of RA...SN.
Saturday Night: Moderate Operational Impact. Likely RA...SN.
Sunday: Moderate Operational Impact. Chance of RA.

&&

.FIRE WEATHER...
A fast moving, weak low pressure area will track east across the
area bringing a few showers tonight. Scattered showers will persist
late tonight into Wednesday away from the Hudson Valley with a
little snow mixed in over higher elevations. Drier weather is
expected for much of the region from Wednesday night into Friday as
high pressure builds east from the Great Lakes region into our area.

Relative humidity values will recover to 80 to 100 percent tonight,
drop to 50 to 80 percent on Wednesday, recover to 75 to 90 percent
Wednesday night, and fall to 40 to 55 percent on Thursday.

Winds will be west to northwest around 5 mph tonight, northwest at 5
to 15 mph Wednesday through Thursday with gusts up to 35 mph
on Wednesday.

&&

.HYDROLOGY...
No hydrologic issues are anticipated through the week. Some
scattered rain and snow showers are expected through the
overnight hours into Wednesday morning with total liquid
equivalent amounts a tenth to a third of an inch. Dry weather
is expected the rest of the week with the next chance for some
wet weather occurring 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...SND
NEAR TERM...SND/11
SHORT TERM...11
LONG TERM...Speciale
AVIATION...SND
FIRE WEATHER...MSE/11
HYDROLOGY...MSE/11
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