Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 182243
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
543 PM EST Mon Dec 18 2017

.SYNOPSIS...
Our weather will continue to be cloudy and unsettled into
Tuesday night with chances for precipitation especially across
the higher terrain. Brief warm up Tuesday with highs about 10
degrees above normal in the mid 30s to mid 40s with seasonable
temperatures back for Wednesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Light precipitation continues north a warm front as an approaching
a short wave move through the fast zonal flow. The boundary
snakes across east central New York into southern New England.
Temperatures are still at or below freezing across portions of
the Mohawk Valley, upper Hudson Valley and southern Vermont.
Temperatures will rise a bit or remain steady much of the night
as the boundary lingers across the region. Chances for the
light precipitation will decrease as the short wave moves to our
east this evening. Used the top-down approach to generated the
weather.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
The warm front will finally lift north Tuesday as the stronger
short wave approaches and we will experience a brief warm up.
Temperatures will be about 10 degrees above normal in the warm
sector with highs in the mid 30s to mid 40s. Chances for precipitation
will increase as the the short wave approaches and with the
milder air in place mainly rain showers are expected with snow
showers more limited to the higher terrain.

With the passage of the short wave and a surface cold front
colder air will be ushered back into region Tuesday night into
Wednesday. A surface low is expected to develop over northern
New England by Tuesday evening. Winds will become brisk and
gusty across the region between this departing deepening low
and an advancing high. The flow will become favorable for some
lake enhance snow showers Wednesday especially in the morning. A
reinforcing boundary will swing through Wednesday shifting the
winds to the north ending the threat for lake effect, however
even colder air will be drawn in. Wednesday night will be
another cold one with lows mainly in the single digits and
teens.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
An active period ensues for the long term thanks to an amplifying
positively tiled longwave trough in the Rockies/Central U.S and a
strengthening sub-tropical ridge centered off the coast of Florida.
Such a set-up will lead to a strong low/mid-level baroclinc zone
stretching from the Gulf Coast States into the Northeast and a
southwesterly flow regime for eastern NY/western New England.
Thus, we will be watching for multiple threats for mixed
precipitation events for the upcoming holiday weekend.

Before we enter the busy stretch of weather for the weekend, we begin
Thursday on a dry yet cold note as Canadian high pressure moves
into the region. Temperatures start off cold in the single
digits/teens Thursday morning and only warm into the 20s (teens
in the Dacks). Despite the colder temperatures, subsidence under
the incoming high should lead to mostly sunny skies. There is
an impulse passing well to our south in the mid-Atlantic that
bares watching but the high should keep it suppressed.

Mostly sunny skies mix with increasing clouds as our high
shifts east and the upper level flow backs to the southwest
heading into Friday. The ECMF and GFS are in fairly good
agreement that a 300mb jet in the Great Plains develops and
intensifies Friday - Sunday (reaching 160 - 190kt by Monday) as
our the aforementioned positively longwave trough and sub-
tropical ridge both amplify. Multiple shortwaves round the base
of the longwave trough sending both northern stream and southern
stream energy into the Great Lakes/southern Canada.

The first disturbance that we need to watch arrives Friday -
Saturday with the surface low tracking well to our west into the
Great Lakes. This track means we should experience overrunning
precipitation initially. With the cold Canadian high from
Thursday shifted into the Canadian Maritimes and a cold air
damming situation possible, initial precip should fall as snow
before enough warm air advection leads to warming aloft. In
these situations, cold air is often stubborn to leave the low
levels and we could see a transition to wintry mix. Have
reflected the threat for a switch from snow to sleet and
freezing rain in our CWA for daytime Friday into Friday night.
Still much uncertainty on just when the warm front crosses the
area but for now, thinking temperatures warm overnight in the
valleys with the Adirondacks/Lake George/southern VT areas struggling
to transition. Most areas should be all rain by Saturday.

Above normal temperatures expected Saturday as we enter into the
warm sector with highs in the 40s but as the cold front closes
in, showers may end as snow, especially across higher terrain
later Saturday. Temperatures behind the front are not very cold
and we stay seasonable Sat night/Sunday. For Saturday night,
some wrap around/Lake enhanced snow showers could occur but
widespread precip should be move offshore. We will then have to
watch for another potential wave of low pressure tracking along
the first system`s cold front Sunday - Monday. Seasonable
temperatures with high in the mid 30s/low in the mid 20s means
precip with this next wave could arrive as snow or a wintry mix
later Sunday or Sunday night.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
A warm front is currently draped across the forecast area from
the Schoharie Valley southeastward into Litchfield county, CT.
North and east of this boundary, light rain/snow showers have
been falling, affecting mainly KGFL. However, light showers
cannot be ruled out of KALB/KPSF. Overall, flight conditions
have been MVFR/IFR and this should continue through at least the
evening. There is potential for BR and lower CIGS overnight as
low level moisture increases behind the warm front, if it
indeed lifts through the remainder of the region.

South winds at 4-8 KT will continue through this afternoon,
then become light/variable again after sunset. Winds will once
again increase and become breezy (out of the southwest) late
tomorrow morning.

Outlook...

Tuesday Night: Moderate Operational Impact. Chance of SHRA.
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: No Operational Impact. NO SIG WX.
Friday: Moderate Operational Impact. Chance of RA...SN.
Friday Night: High Operational Impact. Likely RA.
Saturday: High Operational Impact. Likely RA.

&&

.HYDROLOGY...
No hydrologic problems are expected this week. Ice will continue
to form on areas lakes 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.

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.

&&

$$
SYNOPSIS...IAA
NEAR TERM...IAA
SHORT TERM...IAA
LONG TERM...Speciale
AVIATION...KL/JVM
HYDROLOGY...IAA



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