Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kaly 070907 
afdaly

Area forecast discussion
National Weather Service Albany New York
407 am EST Sat Dec 7 2019

Synopsis...
high pressure will move eastward across the region this weekend
resulting in fair but cold weather. Our next weather system
moves into the northeast early in the work week bringing in
milder temperatures and a widespread rainfall.

&&

Near term /until 6 PM this evening/...
some lake effect snow shower activity is extending into the
western Mohawk Valley, southern Adirondacks and Schoharie valley
as one last piece of upper energy exits the Great Lakes. The
snow shower activity is expected to end by midday when the mixed
layer becomes more shallow and high pressure continues to build
in. Areas from the Hudson Valley into western New England will
see intervals of clouds through the morning while western areas
will see a mostly cloudy sky. The sky will then trend to mostly
sunny through the afternoon as the high pressure builds in.

Highs in the upper 20s to lower 30s with some mid 30s possible
in the Mid Hudson valley and around 20 to mid 20s northern
areas.

&&

Short term /6 PM this evening through Monday night/...
clear and Cold Saturday night as high pressure will be overhead
but then the low level ridging builds east and south low level
flow begins. Weak warm advection begins Sunday morning and
strengthens Sunday afternoon as south winds could get breezy at
times. Some high clouds could begin to spread over the region.
Highs Sunday in the mid to upper 30s but near 40 Mid Hudson
valley and around 30 to lower 30s higher terrain.

Thin high clouds and some decoupling of winds Sunday evening
should support temperatures dropping a couple of degrees before
thicker clouds come in and temperatures rise between midnight
and daybreak. There are some disagreements in guidance as to
the timing of the onset of precipitation, either around daybreak
Monday or later Monday morning. If the precipitation arrives
early, then there could be some mixed precipitation north of the
Mohawk Valley into southern Vermont but just small chances.

Temperatures rise Monday morning as low level boundary layer
flow increases, low level forcing and isentropic lift increases
and precipitation spreads over the entire region. How much
temperatures rise is in question as ageostrophic low level flow
is east to northeast and the full retreat of the cold airmass is
in question. Still, with south to southwest strong boundary
layer winds, there should be some warming at the surface, even
with the rain becoming widespread. Highs Monday in the 40s to
near 50 but lower 40s northern areas. Rain continues Monday
night as temperatures stay above freezing in all areas.

&&

Long term /Tuesday through Friday/...
in the long term, we are looking for above normal temperatures with
rainfall Tuesday, followed by sharply colder air with snow showers
and lake effect snow Wednesday and Thursday and cold but fair
weather on Friday.

The combination of warm temperatures generally in the 40s to lower
50s, dewpoints in the 40s, and rainfall will lead to ripening of the
snow pack and some melting and runoff, although how much is
still questionable. Some flooding is possible Tuesday into Wednesday.

Low pressure will be over Quebec Tuesday morning, with an eastward
moving cold front trailing southwest from about Buffalo to Cleveland
to Cincinnati. We will be in warm sector with southwest flow aloft.
Tuesday may start cloudy with just scattered showers, but low level jet looks
to increase, peaking around 50kt, Tuesday afternoon and evening just
ahead of the cold front as it progresses eastward. Combination of
low level jet forcing, lift from cold front and precipitable water
values of 0.75-1.00 inches later Tuesday into Tuesday evening should
allow for a period of moderate, possibly heavy, rain just ahead of
cold front.

ECMWF, has a slightly slower cold frontal passage Tuesday evening
and a wave developing on the front with an anafront look where
precipitation could end as a significant period of snow Tuesday
night. European model (ecmwf) may be on to something as upper level jet position
Tuesday night is very similar in both Euro and GFS solutions.

Tuesday night into Wednesday night, sharp cold advection will occur
with 850 mb temps falling to -15 to -20c. There will likely be lake
effect snow downwind of Lake Ontario Wednesday and Thursday. Low
level instability may lead to scattered snow showers all areas on
Wednesday. Lows Wednesday morning from the teens across the southern
Adirondacks to around 30 in the Mid Hudson valley. Highs Wednesday
from around 20 in the southern Adirondacks to the mid 30s in the Mid
Hudson valley.

For Thursday and Friday, a drying trend will occur, aside from
areas downwind of Lake Ontario, where lake effect snow will
continue into Thursday. High pressure is forecast to cross the area
on Friday, keeping temperatures cold but with dry weather expected.
Lows in the single digits and teens both nights with highs on
Thursday in the teens and 20s and on Friday in the mid 20s to mid
30s.

&&

Aviation /09z Saturday through Wednesday/...
high pressure will build into the area from the upper Great
Lakes. However, a weak shortwave aloft will move across the
region overnight. Mainly VFR ceilings expected overnight with
patchy MVFR. A few snow flurries are also possible overnight.
Cloud cover will dissipate later on Saturday with skies clearing
around 08/00z.

Northwesterly winds will remain gusty at kalb and kpsf around 10
to 20 kt through most of the night. Elsewhere, winds will be
less than 7kts and variable. Winds will be northwesterly at
5-10 kt on Saturday. Winds turn westerly and diminish to 5 kt or
less after sunset Saturday evening.

Outlook...

Sunday night: high operational impact. Breezy slight chance of rain.
Monday: high operational impact. Definite rain.
Monday night: high operational impact. Definite rain.
Tuesday: high operational impact. Likely rain showers.
Tuesday night: moderate operational impact. Scattered rain showers...shsn.
Wednesday: moderate operational impact. Chance of shsn.
Wednesday night: moderate operational impact. Chance of shsn.
Thursday: no operational impact. No sig weather.

&&

Hydrology...
temperatures will remain below normal through Sunday, so little
melting and/or runoff is expected through the weekend. This will
allow the snow pack to be maintained and for some ice to build on
shallow waterways, especially during the overnight hours.

Temperatures will likely rise to above normal values by Monday into
Tuesday, with periods of rain likely. There is uncertainty with the
amount and placement of the heaviest rain, with some models
indicating potential for 0.50-1.50 inches, and others 1-3
inches. Either way, at least some ripening and melting of the
snowpack and runoff is expected, although it is too early to
determine if there will be a flooding threat during this period.
Rises on area waterways are likely during this timeframe.

It will turn sharply colder from Wednesday through the end of the
week, which should put a stop to any melting/runoff, and allow river
levels to recede.

For details on specific area rivers and lakes, including latest
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.
New York...none.
Massachusetts...none.
Vermont...none.

&&

$$
Synopsis...NAS
near term...NAS

National Weather Service Glossary of Abbreviations