Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 200241

Area Forecast Discussion
National Weather Service Albany NY
1041 PM EDT Mon Mar 19 2018

High pressure will continue to allow for a cold northerly flow into
the region tonight into tomorrow, with mainly clear skies and below
normal temperatures. A storm system may impact portions of the
region Wednesday, mainly south of Albany, with an accumulating
snowfall. Several inches may occur over the mid-Hudson Valley and in
northwestern Connecticut. Dry weather is expected Thursday into
Friday, along with temperatures remaining below normal.


As of 1040 PM EDT...High pressure continues to dominate with
fair and cold weather, as it ridges south/southeast from north
central Ontario and Hudson Bay. Lowered temps a few degrees in
the southern Adirondacks/Lake George Region to reflect ideal
radiational cooling conditions tonight with clear skies, light
to calm winds, and snow cover in place. Lows in the teens from
the Capital District south down the Hudson River Valley and NW
CT with upper single digits elsewhere, except below zero
readings over the southern Adirondacks.

We remain within a pronounced zonal flow across the northeast
corridor which in turn should hold back the Ohio
Valley/Tennessee Valley system through the day Tuesday, outside
of some increase cloud coverage south of I90.

We will undercut guidance a degree or two. Lighter winds for
Tuesday under a good deal of sunshine with a blended MOS
approach for highs which equates to 30s for most locations.


Complex winter storm will take shape over the mid-Atlantic
during this period with the northern edge of the the
precipitation still in question as it affects our area. Mid-
level low pressure will deepen over the central Appalachians
Tuesday night into Wednesday with associated low pressure
developing off the east coast. Meanwhile mid- level low
pressure will be spinning over the Canadian Maritimes and will
tend to block this storm from moving up the coast as far north
as the last few storms. Models continue to show some run-to-run
differences and ample convection during the development stages
of the system over the southeast U.S. will keep some uncertainty
in the forecast. The latest runs of all of the operational
models have indicated a northward trend with this system along
the mid-Atlantic coast allowing for a winter storm threat for
our southern counties from the mid-Hudson Valley into
Connecticut. Based on this we have issued a winter storm watch
for the mid-Hudson Valley into western Connecticut for Wednesday
with the understanding that there is still ample uncertainty
on where the northern edge of the heavy precipitation
eventually sets up.

Initial low pressure developing off the coast will move east
south of Long Island Tuesday night. An area of light snow will
be passing mainly south of our area during that time with some
snow possibly brushing the southern edge of the mid-Hudson
Valley and northwest Connecticut. The main system will develop
on Wednesday as another low pressure area develops off the coast
with the main mid-level low center advancing east from the
Appalachians toward the coast. The surface storm will deepen
into the 980`s while mid-level low pressure advances east off
the Delmarva coast setting the stage for moderate to heavy
precipitation with pivoting snow bands from southern New England
back to eastern Pa. The mid-level low center eventually pulls
off to the east-northeast passing well to the south of Cape Cod.
This pattern would result in most of the precipitation falling
south and east of the Capital District with heavy snow potential
still in play for the mid-Hudson Valley into western
Connecticut Wednesday into Wednesday night.

Northwest flow behind the system later Wednesday night into
Thursday could result in a few flurries or light snow showers
for the higher terrain especially west of the Hudson Valley,
otherwise dry and continued chilly weather will return to all
areas Thursday into Thursday night.


The atmospheric pattern turns complex for the long term with
temperatures expected to run 5-10 degrees below normal through early
next week.

Friday will feature a longwave trough over the eastern CONUS/western
Atlantic with strong ridging over the Central Plains. Weak north-
northwest flow over the Northeast should lead to some cold air
advection so I decreased high temperatures a few degrees into the
mid-upper 30s. Within the longwave trough during the day Friday, a
shortwave looks to travel from the Great Lakes into the Northeast.
While the passage of a shortwave and trough axis typically
introduces the potential for snow showers and even snow squalls, the
moisture aloft is low so for the time being, only have slight chance
POPs in the Adirondacks. However, given that BUFKIT profiles show a
well-mixed and deep boundary layer extending up to around 750mb with
rather steep lapse rates, we will continue to watch the potential
for snow showers/snow squalls in future updates. Most of the latest
guidance is in agreement that the trough axis exits into eastern New
England by 00z Saturday.

A reinforced shot of cold air advection and subsidence behind the
departing trough axis should lead to clearing skies and cool low
temperatures Friday night in the low - mid 20s. Below normal
temperatures continue into Saturday as cyclonic flow remains in
place over the Northeast. The strong ridge from the Central Plains
tries to shift into the Northeast Saturday but it looks to become
flatten by a second, more potent shortwave from the Hudson Bay that
dives southward. This is an important feature to note because the
latest guidance continues to show a low pressure system intensifying
in the Midwest/Ohio Valley during this time. The flatten ridge gives
way to more zonal flow over the Eastern CONUS which would allow the
developing low to track into the mid-Atlantic.

By Sunday, the broad cyclonic flow remains in place over the
Northeast with a strong 1040-1045 high over northern Canada slowing
sinking southward. In fact, there are signs of a potential back-door
cold front that could reach into the eastern half of our CWA. Either
way, these features could act as a block to the approaching low and
suppress the moisture south of our CWA. Interestingly, the 700mb
pattern on Sunday shows a sharp baroclinc zone and moisture
difference between the mid-Atlantic and Northeast so there could be
a sharp snowfall gradient on the system`s northern fringe. Much
uncertainty remains on the low`s track with the 12z Canadian and
ECMWF showing some moisture scraping the southern half of our CWA
but the GFS shows it well to our south. For the latest update,
continued slight chance POPs for the northern half of the CWA on
Sunday and chance POPs for the southern half.

High pressure from northern Canada should then take control for
Monday/Tuesday with temperatures remaining below normal. Highs
remain in the low-mid 40s and lows in the low-mid 20s (normal highs
for late March is closer to 50 and lows in the upper 20s).


High pressure centered over north-central Ontario and Hudson Bay
will continue the fair weather over eastern NY and New England
the next 24 hours with VFR conditions.

Some mid and high clouds will increase near KPOU after 22Z/TUE
as a coastal low begins to move northeast from the Carolinas.

The winds will become light calm tonight, and then be from the
north to northeast at less than 10 kts late tomorrow morning
through the afternoon


Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: Moderate Operational Impact. Chance of SN.
Wednesday Night: Moderate Operational Impact. Chance of SN.
Thursday to Saturday: No Operational Impact. NO SIG WX.


The Fire Weather season has officially begun across eastern New
York and western New England. Despite this, snow cover is in
place across much of the region, which will mitigate any
potential fire weather hazards for the time being.

High pressure over central Canada will allow for a cold northerly
flow into the region tonight and tomorrow, with a partly to mostly
sunny sky and well below normal temperatures.  A storm system will
pass by to the south on Wednesday, which may bring some snow, mainly
to our southern areas. Dry weather will return to all areas on
Thursday into Friday along with below normal temperatures.


No hydrologic issues are anticipated through the week.

Mainly dry weather is expected through the week across the
entire area. The exception may be far southeastern areas could
see some light snow on Wednesday, but liquid equivalent amounts
will be under two tenths of an inch.

A slow diurnal snowmelt is expected over the next several days,
with temperatures above freezing during the day, and below
freezing at night. There will be little impact on the waterways
with minimal, if any, rises.

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.


CT...Winter Storm Watch from late Tuesday night through Thursday
     morning for CTZ001-013.
NY...Winter Storm Watch from late Tuesday night through Thursday
     morning for NYZ064>066.


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