Albany Office Forecast Discussion

373
FXUS61 KALY 191734
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
134 PM EDT Tue Mar 19 2019

.SYNOPSIS...
An upper level disturbance will bring some isolated to
scattered snow showers today, otherwise it will be fair and dry
with high pressure building in. The surface high will bring cold
and dry conditions tonight. On Wednesday, the high moves east
of New England with a southerly flow of milder air allowing
temperatures to rise above normal. The next low pressure system
arrives from the west late Wednesday night into Thursday with
widespread rain and snow showers.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 12:15 PM EDT, Cloudiness is increasing due to days
heating and now extends from Mohawk Valley east to southern
Vermont and Berkshires southwest to eastern Catskills.
Elsewhere, skies are mainly clear. Radar shows some scattered
snow showers and flurries where cloudy. Temperatures range from the
upper 20s in the hill towns to around 40 in the mid Hudson
Valley. Winds are generally from a northwest direction and
beginning to become gusty. Pittsfield gusting to around 30 MPH
this hour.

Previous... A cyclonic flow of chilly air aloft will continue
over the region one more day. The H500 upper level trough will
still have a cold pool of -30C to -36C air over much of upstate
NY and New England. In the west to northwest flow, some
instability diurnal cumulus will likely form, and some Lake
Ontario moisture will be tapped for some isolated to scattered
lake enhanced snow showers and flurries, especially west of the
Hudson River Valley.

A weak H500 impulse will attempt to focus any isolated snow
showers and flurries. We increased the PoPs with this update for
the western Adirondacks, western Mohawk Valley, and northern
Catskills based on the upstream radar trends where the snow
showers are increasing across western and central NY.  The
boundary layer may warm enough for light rain to mix with the
snow in the valley areas. Some light dustings to a half inch are
possible over the higher terrain. Isolated one inch amounts are
possible over the western Dacks. High pressure at the surface
will be building in from the OH Valley, and Pennsylvania late in
the day. H850 temps will be in the -8C to -12C range.

Sunshine will mix with clouds, and max temps will be in the
upper 20s to mid 30s over the mtns, and mainly upper 30s to
lower 40s in the lower elevations, though some mid 40s are
possible in the mid Hudson River Valley and southern Litchfield
Co. CT. West to northwest winds will be in the 5 to 15 mph
range.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
Tonight...The sfc anticyclone builds in from from just off the
NJ Coast over NY and New England with mostly clear skies and
light to calm winds for near ideal radiational cooling
conditions. The mid and upper level flow becomes flatter, as the
upper trough moves downstream. Lows will be in the mid teens to
mid 20s across the forecast area.

Wednesday...A nice day is expected to open astronomical spring
with the return flow from the retreating sfc high off the New
England Coast allowing temps to rise above normal. Spring
begins at 558 pm EDT. In the warm advection pattern, H850 temps
increase to -3C to -5C. Some cirrus may increase during the mid
to late afternoon, but expect partly to mostly sunny
conditions, and max temps to be about 5 to 7 degrees above
normal with southerly winds in the 10 to 15 mph range. Highs
will get into the upper 40s to lower 50s in the lower elevations
with upper 30s to mid 40s over the higher terrain.

Wed night into Thu...A northern stream positively tilted mid and
upper level trough will be approaching NY and New England Wed
night. The trough digs equatorward and attempts to phase with
southern stream energy moving across the Southeast and into the
Ohio Valley.  Southwest flow sets up across the region. A low-
level jet at 850 hPa increases to 40-50 kts across the region
between 06Z-12Z. The increasing low-level jet will tap some gulf
moisture and help enhance the isentropic lift for some rain and
snow showers to the overspread the region in the early to mid
morning hours. We slowed the trend of the pcpn this cycle based
on the slower timing with the guidance and the phasing of the
two troughs potentially. Lows will be in the mid 20s to mid 30s.
We have the highest POPS prior to daybreak west of the Hudson
River Valley in the high chance to likely range.

The southwest flow will also favor some orographic enhancement
over the southwest Adirondacks in n-cntrl Herkimer to southwest
Hamilton Counties through Thursday morning where 1-3" or
possibly some isolated 2-4" of wet snow accumulation are
possible. The southern Adirondacks and southern Greens could
receive 1-3" of snow with an inch or less over the Berkshires
and eastern Catskills. Any snow in the lower elevations would be
a light coating on the grassy surfaces as the boundary layer
warms considerably. Otherwise, the warm advection and increasing
southerly flow ahead of weakening low pressure over the eastern
Great Lakes Region, and the developing secondary low over
eastern VA and the Delmarva Region THU afternoon will bring
periods of showers during the afternoon. We have PoPs in the
likely range during the afternoon, as an inverted sfc trough
north of the secondary cyclone will focus the pcpn. Highs may
only get into the mid 30s to around 40F over the mtns with 40s
to lower 50s in the valleys and over the hills.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Model guidance has come into better agreement regarding the
development of a potential coastal low pressure system Thursday
night into Friday morning, although there are significant
position/track differences among the GFS/ECMWF/NAM/CMC. The GFS and
the GEFS ensemble mean are on the eastern envelope of solutions with
a track mainly off shore to near Cape Cod, while the NAM and ECMWF
are farther the west from the Delmarva to southeast New England. The
NAM/ECMWF camp would result in greater QPF and precip lasting
through much of Thursday night, while the GFS has much lighter QPF
and is more progressive. Main point at this time is there is
consensus for a coastal storm with high enough confidence to mention
likely pops across the SE 2/3 of our area. Precip type will be
another challenge, as models indicating low level thermal profiles
to be rather warm regardless of storm track. Expecting snow or
rain/snow mix to be across higher terrain areas, with the threat of
accumulating snow confined to mountain areas at this time. However,
this is still a low confidence forecast due to track/QPF/p-type
issues so a lot could still change from now until Thursday night.

On Friday, there is growing model consensus that a strong northern
stream upper level low will rapidly dig southward across SE Canada
and the eastern Great Lakes. Cyclonic vorticity advection along with
terrain forcing associated with NW flow will result in scattered
valley rain showers and numerous mountain snow showers. There could
be some light snow accumulations, especially for favored upslope
areas of the western Adirondacks and southern Green Mountains.

As the upper low merges with the trough from the coastal storm, the
surface cyclone is forecast to deepen considerably by Friday night
in the vicinity of northern Maine. This will result in a
strengthening pressure gradient and potentially strong northwest
winds developing across our region Friday night and lasting through
Saturday, as the storm system starts to become vertically stacked
and does not make much eastward progress. Blustery and cold
conditions expected on Saturday, although snow shower activity
should be diminishing as the flow pattern becomes more neutral.

Dry and cold conditions in store for Saturday night, as the storm
system pulls farther away in the Canadian Maritimes. Sunday looks to
feature warmer temperatures as heights aloft are forecast to rise
along with abundant sunshine. The next chance of showers arrives on
Monday, as a strong cold front sags southward from Canada while some
moisture pools along the front as a weak wave of low pressure may
develop.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
High pressure continues to build in tonight, providing mainly
dry conditions. With cold air aloft, SCT-BKN afternoon cumulus
clouds will continue with VFR conditions prevailing through the
24 hour TAF period ending 18Z Wednesday. A brief snow shower or
flurry is possible at KPSF between 18 and 22Z, but should not
restrict visibility below 6SM.

Winds today will mostly be northwest around 10-15 kt, becoming
calm after dark this evening. However, this afternoon, deep
mixing of the lower atmosphere will mix down some 30 KT
northwesterly wind gusts from aloft. Gusty NW winds have been
included in the TAFs in a TEMPO from 18-22Z.

Outlook...

Wednesday Night: Low Operational Impact. Slight Chance of SHRA...SHSN.
Thursday: High Operational Impact. Likely SHRA.
Thursday Night: High Operational Impact. Likely RA.
Friday: Moderate Operational Impact. Breezy Chance of SHRA.
Friday Night: Low Operational Impact. Breezy Slight Chance of SHRA...SHSN.
Saturday: Low Operational Impact. Breezy NO SIG WX.
Saturday Night: Low Operational Impact. Breezy NO SIG WX.
Sunday: Low Operational Impact. Breezy NO SIG WX.

&&

.FIRE WEATHER...
An upper level disturbance will bring some isolated snow
showers and flurries mainly west of the Hudson River Valley today,
otherwise it will be fair and dry with high pressure building in. The
surface high will bring cold and dry conditions tonight, before
moving east of the New England Coast with a southerly flow of milder
air allowing temperatures to trend above normal for Wednesday.
The next chance of widespread precipitation will be late
Wednesday night through Thursday.

Most of the higher terrain remains snow covered. The RH values
will lower to 30 to 60 percent this afternoon, and then recover
to 75 to 100 percent Wednesday morning. The minimum RH values
will be in the 30 to 55 percent range Wednesday afternoon.

The winds will be west to northwest at 5 to 15 mph today and
light and variable at less than 5 mph tonight. Expect southerly
winds on Wednesday of 5 to 15 mph.

&&

.HYDROLOGY...
No widespread hydrology problems are anticipated through much of
the the next week.

Forecast liquid equivalent precipitation for the next 7 days is
three quarters of an inch or less. However, some of the medium
range guidance (ECMWF) as well as the NAM does bring a half an
inch to an inch or more of liquid equivalent Thursday into
Friday from a slow moving low pressure system. This continues to
be monitored closely, as some within bank rises on rivers would
be possible with higher QPF.

Overall, forecast temperatures will generally be near to below
normal. Low temperatures are forecast below freezing on most
nights

The combination of the possibility of low precipitation, low
maximum temperatures amd dew point temperatures below freezing
should lead to orderly snow melt and minor changes in river
flows.

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/Wasula
NEAR TERM...SND/Wasula
SHORT TERM...Wasula
LONG TERM...JPV
AVIATION...SND
FIRE WEATHER...Wasula
HYDROLOGY...SND/Wasula

NWS ALY Office Area Forecast Discussion