Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kaly 221435 
afdaly

Area forecast discussion
National Weather Service Albany New York
935 am EST Mon Jan 22 2018

Synopsis...
a frontal boundary will lift slowly north of the region
as a warm front today into tonight with light mixed precipitation
changing to rain especially north of the Mohawk Valley and capital
region. A low pressure system and its cold front will bring periods
of rain to eastern New York and western New England on Tuesday. As
the cold front moves through Tuesday night, colder more seasonable
air will return with brisk conditions for the mid week.

&&

Near term /until 6 PM this evening/...
a Winter Weather Advisory remains in effect from 1 PM today
until 7 am Tuesday for Hamilton and northern Washington and
Warren counties in New York, and southern Vermont...

Most of the rain and drizzle has exited the region but there
are areas of fog. Guidance suggests some of the patchy light
precipitation in central and western New York expands as it tracks
east and becomes an areas of steady light rain over our region
later this afternoon. Indicating just slight chance to chance
through early afternoon then increase to likely later this
afternoon in anticipation of the expansion of the area of light
precipitation. Light winds, fog and snow/ice on the ground could
anchor cold air in place. So, nudged temperatures down a little
through this afternoon. Previous afd has more details and is
below...

Previous near term...

The latest water vapor loop with h500 heights overlaid has
zonal flow over the northeast and southeast Canada with a strong
closed/cutoff cyclone over the Central Plains. A region of
upper level diffluence is moving over the Great Lakes region and
Ohio Valley upstream of the region. At the sfc, high pressure
remains near northern Ontario and James Bay with a frontal
boundary over northern New York and northern New England. This front
has become stationary. A separate frontal boundary is over the
New York and PA border as well as central New Jersey.

Between noon and 3 PM another surge of warm advection and
isentropic lift occurs across the forecast area from the west to
southwest to north to northeast, as the warm front and mid-
level short-wave moves in. Critical partial thicknesses, and
model soundings support mainly a rain ptype from the Mohawk
Valley, capital region, Berkshires south. Further north some
snow, sleet and freezing rain is likely especially late in the
PM towards sunset. We favored the colder NAM profiles where the
colder subfreezing air may be hard to dislodge especially east
to the southern Adirondacks, and southern green mtns where the
boundary layer ageostrophic winds are from the east to northeast
with wet bulb zero temps below 0c. Some light accums are
possible especially towards sunset. Any sleet and snow accums
should be light on the order of a coating to perhaps a half an
inch.

Temps are tricky today with clouds and moisture increasing in
the boundary layer. We sided with the colder NAM and ecm MOS
temps and not the much warmer gfsmos values. We went with highs
mainly in the upper 30s to lower 40s from the capital
region/Mohawk Valley south and west. A few mid 40s are possible
in these areas, and lower to upper 30s north and east. Patchy
fog may linger with the spotty light rain or mixed pcpn during
the day.

&&

Short term /6 PM this evening through Wednesday night/...
tonight...the NAM model soundings in particular near kgfl and
southern Vermont keep the threat for some freezing rain tonight
before temps gradually warm up, as the warm front lifts north
and east. We added southeast Warren and northern Washington
counties to the advisories until 7 am Tuesday. The eastern
Adirondacks including Hamilton and northern Warren counties were
kept going, as well as southern VT, though west of the southern
greens mtns may warm up quickly. Will have to watch if northern
Saratoga co. Needs to be added to the advisory.

The good news is the isentropic lift strengthens on the 290/295k
surfaces as the low-level jet increases. Temps should steadily
rise Mon night with lows generally in the mid and upper 30s from
the I-90 corridor south and east, and upper 20s to mid 30s
northward. The south to southwest h850 jet increases to 40-50
kts on the GFS/NAM. The latest 00z gefs indicate the h850
+v-component low-level wind anomalies increase to +2 to +3
Standard deviations /std devs/ above normal. The strong
southerlies will advect into the region some Gulf moisture
towards daybreak, as precipitable water anomalies also rise 2 to 3+ Standard
devs above normal ahead of the cold front and strong cyclone
moving into the central and eastern Great Lakes region. Any ice
accretions should only amount to a few hundredths to isolated
tenth of an inch, as the warmer air floods into the the region.

Tuesday...a slug of moderate to heavy rainfall impacts the
region as upper level diffluence sets up over the area. The
isentropic lift enhances with better upper level jet dynamics.
The heaviest rain looks to be Tuesday morning into the early to mid
PM. The showalter values continue to dip to 0c to -2c south of
Albany. The elevated instability is best depicted on the NAM,
and we did include a slight chance of thunderstorms late Tue
morning into the afternoon south of Albany over the southeast
Catskills, Mid Hudson valley, southern Taconics and northwest CT. A dry
slot to the system will likely drift into the region Tuesday PM, as
the sfc wave stays north and west of the region, as it moves
north of the St Lawrence River valley. Total rainfall may reach
the half inch to one inch range during this time frame. High
temps will be in the mid 40s to lower 50s across the forecast
area, but strong cold advection will kick in late in the day
initially northwest of Albany.

Tuesday night...some timing differences in the
NAM/GFS/ECMWF/ensembles on how quickly the cold advection moves
across the forecast area. The GFS has two surges. One is with
the initial cold front, and the second is with a secondary
boundary. The mins temps are bit higher on the gfsmos compared
to the NAM MOS. We used a blend of the guidance, and have the
lingering pcpn with the upper low and secondary cold front
changing to snow north and west of the capital district. Light
snow accums in the westerly upslope region of the western
Adirondacks, and southern greens are possible with a few tenths
to an inch or two. Also, some light snow accums are possible in
the Mohawk Valley/northern and eastern Catskills. The winds will
also increase from the west to northwest at 10 to 20 mph with
some gusts in the 35-40 mph range. Lows fall back into the 20s
to around 30f with some teens over the southern dacks. We will
have to monitor if any Hydro issues arise. After collab with
neighboring wfos, we decided to hold on a Flood Watch for snow
melt/runoff/ice jams. Still time to further assess potential.
Please see our Hydro section for more details.

Wed-Wed night...the cyclone deepens and strengthens over New
Brunswick and Nova Scotia. Blustery northwest winds and cold
conditions are expected on Wednesday with h850 temps tumbling back to
-10c to -16c over the fcst area.

Max temps may be achieved before noon, and slightly fall during
the day. Some wind gusts in to 35 to 45 mph range will be
possible over the higher terrain and from the capital region
north and east late morning into the early PM. Daytime highs
will be in the 20s to mid 30s. The upslope or lake enhanced snow
showers will diminish during the day with the subsidence
inversion lowering. Clearing skies, lighter winds and cold
conditions are likely late Wed night with lows in the single
digits and teens with some below zero readings over the southern
Adirondacks.

&&

Long term /Thursday through Sunday/...
the periods starts out on Thursday with a cold and dry northwest
flow regime in place, with high pressure building east across the
Great Lakes. 850 mb temp anomalies of -1 to -2 stdev are forecast
from the 00z gefs, which will translate highs only in the teens and
20s across the region with gusty northwest winds. Wind speeds will
decrease Thursday night, as a 1035 to 1040 mb anticyclone moves
directly over the region. This will result in cold temps in the
single digits to below zero in the higher terrain. Even colder temps
would be expected with a fresh snow pack, but this is not
anticipated. Temps will remain on the cool side Friday as the high
pressure ridge gradually shifts eastward into New England, with
continued dry conditions.

As high pressure at the surface moves offshore Friday night, ridging
in the mid to upper levels will build across the region. Rising
heights and a return south-southwest flow around the departing high
will result in warmer temps on Saturday. Depending on eventual
sunshine and mixing potential, many locations from the Mohawk and
Hudson Valley southward could reach well into the 40s. A residual
snow pack in higher terrain areas should keep temps cooler in the
30s, but still above normal for late January.

Chances for precipitation will start to increase Saturday night, and
especially into Sunday ahead of a surface cold front and upper level
trough passage. Forecast guidance has trended towards a progressive
open-wave system, although there are timing differences. Will
mention highest pops during the day Sunday, as this period is when
there is better consensus for the timing of the cold front passage.
Based on temp profiles, there could be some mixed precipitation
across mainly higher terrain areas and sheltered valleys with colder
air in place near the surface Saturday night. Will mention rain/snow
mix for now, with plenty of time to refine forecast once timing
comes into better focus. Primarily rain is expected in most valley
locations Saturday night into Sunday.

&&

Aviation /15z Monday through Friday/...
a frontal boundary draped across the area will result in low clouds
and some fog due to moist air moving over snow pack on the ground.
There still is some spotty light rain or drizzle early this morning,
but there should be a break in the precipitation from later this
morning into the early afternoon. With the low clouds and fog,
flying conditions will generally be IFR or LIFR through much of the
morning although some drier air in place around kgfl expected to
result in MVFR conditions into this afternoon.

Additional precip will move in by mid to late afternoon, as another
surge of moisture moves in well ahead of a sprawling low pressure
system approaching from the Midwest. Temperatures should be above
freezing at the kalb/kpou/kpsf terminals by then, so just plain rain
is expected at these sites. However, colder air should remain locked
in at the surface at kgfl through the day into tonight, so will
mention -fzra there. Conditions should be widespread IFR or LIFR
once the precip moves back in this afternoon. Another break in the
precip should occur starting late this evening, although flying
conditions will likely remain poor with a moist air mass persisting.

Winds will be variable less than 5 kt through 12z Tuesday.

Outlook...

Tuesday night: moderate operational impact. Windy chance of rain showers...shsn.
Wednesday: low operational impact. Breezy no sig weather.
Wednesday night: no operational impact. No sig weather.
Thursday: low operational impact. Breezy no sig weather.
Thursday night: low operational impact. Breezy no sig weather.
Friday to saturday: no operational impact. No sig weather.

&&

Hydrology...
ongoing flooding due to ice jams will continue to be addressed
with areal flood warnings /Warren and Litchfield counties/, as
some lingering issues continue due to existing ice jams which
froze in place.

Temperatures will continue to run above normal into Tuesday.
The mildest night and day will be on Tuesday with highs mainly
in the 40s to lower 50s with a much colder and more seasonable
airmass returning Tuesday night and through the remainder of the
week.

A low pressure system and its cold front will bring a moderate
to locally heavy rainfall to the area. The rain is expected to
be light today and into early tonight with the bulk of the rain
occurring Tuesday morning into early afternoon. Quantitative precipitation forecast amounts are
forecast at this time to range from three quarters of an inch to
an inch an a quarter. The highest amounts are expected north
and east of Albany and the capital region.

The rain is expected to cause rises on rivers and streams, which
may move and dislodge ice and may cause flooding near ice jams.
Mostly within bank rises are expected based on the latest nerfc
forecasts and the mmefs. A couple of points reach minor flood
stage on the mmefs such as Little Falls on the Mohawk River and
Williamstown on the hoosic river. Our confidence is not great
for widespread potential flooding and we will continue to
monitor if one is needed especially Tuesday into Tuesday night.

Our latest winter/Spring flood potential outlook (esfaly) was
issued this past Friday.

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.
New York...Winter Weather Advisory from 1 PM this afternoon to 7 am EST
Tuesday for nyz033-042-043-083.
Massachusetts...none.
Vermont...Winter Weather Advisory from 1 PM this afternoon to 7 am EST
Tuesday for vtz013>015.

&&

$$
Synopsis...wasula

National Weather Service Glossary of Abbreviations