Severe Thunderstorm Warning 134, NWS Albany, NY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
647 PM EST Sun Nov 15 2020

.SYNOPSIS...
Showers will increase in coverage through this evening
ahead of a cold front. A line of showers and isolated thunderstorms
along this front may produce strong winds this evening. It will turn
cooler through midweek with lake effect snow developing downwind of
Lake Ontario.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
As of 630 PM EST, a couple different convective bowing segments
are approaching the western portions of the area. Several
reports of wind gusts in excess of 50 mph have been noted
across western and central portions of the state with these
bowing segments along with reports of trees and power lines
downed. So similar observations are anticipated as the front
pushes through the area. Lightning has diminished but with
various segments strengthening did not want to take out the
slight chance of thunder for the next few hours quite yet.
Therefore, only minor changes were made to freshen up the temps
and PoPs based on radar trends. See previous discussion for
further details...

Prev Disc...
As of 300 pm, vigorous negatively tilted shortwave trough is
near the OH/PA border, with convective line along a cold front
extending across western NY/PA. Areas of rainfall are occurring
downstream in isentropic lift associated with an intense low
level jet. Locally, still likely plenty of dry air at midlevels
preventing rainfall, except some showers are occurring over the
southern Adirondacks and western Mohawk Valley. For the rest of
today into the evening, the shortwave and cold front will
continue to progress eastward, along with a 140+ kt 300 mb
southwesterly jet max punching into the forecast area. The
pressure gradient will tighten ahead of the front this afternoon
with south to southeasterly winds increasing with gusts to
25-45 mph. Increasing saturation in the 3-5kft AGL layer will
likely prevent some of the 40-50 kt winds at 925 mb from mixing
down, but will continue to monitor in case any short-fused wind
advisories become necessary.

CAMs continue to indicate a coherent band or bands of low-
topped convection either from the current upstream activity or
evolving across PA this afternoon, tracking through our
forecast area mainly 6-10 pm. The strong low-level wind field
ahead of (and to a slightly lesser extent, behind) the front
raises concerns about convection mixing these winds to the
surface. Pros for this scenario are CAMs in the HREF suite in
good agreement in an organized line along the front, and
widespread reports of 50-65 mph observed gusts upstream over
IN/OH. Cons are the overall lack of instability (likely 100 J/kg
MLCAPE or less) and questions with regard to low-level lapse
rates as the line may be embedded within a larger stratiform
area of rain. Due to upstream reports and the fact that moisture
advection may compensate for the low level lapse rates,
confidence in strong to locally damaging gusts is increasing,
reflected by the 1630Z SPC upgrade to slight risk in the Mid-
Hudson Valley and NW CT, and marginal elsewhere except for the
southern ADKs/Glens Falls area. Will handle this line with
short-fused SPS/SVRs if necessary.

Winds will remain gusty in the wake of this line overnight,
especially in the higher terrain, with gusts of 25-40 mph
possible amid cold advection. The rainfall should quickly end
after the line passes 00-03Z, but Lake Ontario will become
activated as surface to 850 mb delta-T values increase to 16-17
K/km. With the cooling boundary layer, this may support some
light accumulations of snow over the western Adirondacks 06-12Z.
Elsewhere, lows will mainly be in the 30s with variable cloud
cover.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
Cold, cyclonic flow will be in place over the forecast area during
the short term period. A blustery day is expected Monday with
seasonably cool temperatures. Westerly gusts of 25-35 mph will be
common. Westerly flow across the lake will result in a band of lake
effect snow continuing for areas around the Route 28 corridor with
surface to 850 mb delta-Ts around 16-18 K/km resulting in moderate
instability. Marginal boundary layer temps will prevent
accumulations from getting too out of hand, but a few inches of snow
are possible Monday into Monday night especially over the higher
elevations and along/north of Route 28. Breezy conditions continue
Monday night with partly cloudy skies outside of the lake effect
belt. Lows near normal in the mid-20s to low 30s.

On Tuesday, a shortwave trough embedded in the northwest flow will
track through the forecast area, with a reinforcing shot of cold air
behind it. This will tend to shift the lake effect bands south of
the Route 28 corridor toward the Mohawk Valley. Some snow or
rain/snow mixed showers may even reach the valleys depending on
surface temps. Some heavier snow squalls are possible across the
higher terrain as values of the snow squall parameter increase due
to the colder air being brought across the lake (surface to 850
delta Ts increasing to near 20 K/km with steep low-level lapse
rates). Cool and breezy with highs ranging from the low 30s in the
higher terrain to the mid-40s in the valleys. Modest height rises
Tuesday night will tend to dissipate the lake effect bands with
time. A chilly night expected with lows in the low teens to mid-20s,
with colder wind chills.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Upper level trough will be exiting to the east on Wednesday, but
temps aloft will remain rather chilly.  Surface high pressure will
moving from the Ohio Valley towards the mid-Atlantic States.  As a
result, skies will remain fairly clear through the day, although
without the high directly over the area, there will be enough of a
gradient in place to keep a northwest breeze going.  Despite the
sun, temps will be very chilly for mid-November, with highs only in
the mid 20s to mid 30s and the breeze will make it feel even colder.
Fairly clear skies, diminishing wind and continued dry conditions
will allow for a cold night on Wednesday night, with lows in the
teens to low 20s.

The flow aloft will start to become rather zonal for Thursday, with
westerly flow in place. Dry weather will continue for Thursday as
high pressure passes to the east off the eastern seaboard.  Temps
aloft will be moderating, so highs should reach into the 40s for
most areas (upper 30s for the highest terrain), along with a partly
cloudy sky.  It should be continued dry into Thursday night and
temps won't be as cold as Wed night with lows in the upper 20s to
mid 30s.

By Friday, it will still be dry for most spots, although a stray
shower can't be ruled out across far northern areas as a weak
shortwave passes across southern Canada.  Otherwise, skies will be a
mix of sun and clouds and milder temps aloft should yield afternoon
highs in the mid 40s to mid 50s.  It should stay dry into Friday
night with lows in the 30s.

Over the weekend, a frontal system will gradually be approaching
from the Midwest and Great Lakes region.  Both a warm front and cold
front should bring some chances for showers, with the greatest
threat for northern and western areas.  It may take some time for
this system to reach our area and the timing is still far from
certain, so some/all of the weekend may wind up dry before this
system impacts the area.  Due to the uncertainty, will keep POPs
limited to just slight to low chc for the weekend, with temps close
to seasonal normals.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Mainly MVFR conditions across the TAF sites this evening as
several convective rain bands ahead of the cold front move into
the area. As the heavier bursts of rain occur, expect brief
reduction in visibilities and stronger gusts of wind up to 40
kts, especially at KALB/KPSF. Behind the front (and rain bands),
conditions should improve fairly quickly but winds will remain
gusty for the majority of the period. Decided to keep mention of
lightning for the next few hours for KALB/KPSF/KPOU, though its
looking less likely to occur given recent downward trend in
lightning activity.

Southerly winds at 15-25 kts will remain gusty up to 30-40 kts.
Behind the front, winds will remain gusty but turn out of the
west tonight and through the day tomorrow.

Outlook...

Monday Night: No Operational Impact. NO SIG WX.
Tuesday: Low Operational Impact. Slight Chance of SHRA...SHSN.
Tuesday Night: Low Operational Impact. Slight Chance of SHSN.
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: No Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
Breezy westerly flow continue into tomorrow with sustained winds 10
to 20mph with gusts up to 30 - 40mph. RH values drop to 45 to 60
percent with the lowest values in parts of NW CT and the mid-Hudson
Valley. Lake effect snow bands downwind of Lake Ontario are also
expected to impact the southern Adirondacks and the western Mohawk
Valley but other areas likely remain dry.

RH values rebound to 75 to 85 percent tomorrow night with winds
weakening overnight to 5 to 10mph. The potential for lake effect
snow continues into Tuesday as a reinforcing shot of cold air moves
into the region. Winds will not be as breezy, only sustained 6 to
12mph.

&&

.HYDROLOGY...
An initial area of showers late this afternoon will be followed by a
convective line early this evening capable of brief heavy downpours,
isolated thunderstorms and strong/gusty winds. Heavy downpours may
produce a quick 0.25 - 0.50 inch of rain but given the fast paced
nature of any thunderstorms and dry antecedent conditions, flooding
is not expected. Total rainfall amounts are expected to range
between 0.25 and 0.75 inches with up to an inch highest over the
higher terrain of the Catskills, Adirondacks, and Greens.

Lake effect snow develops as this system departs late tonight
through Tuesday mainly for areas downwind of Lake Ontario. A
cooler airmass may promote ice formation on waterways over the
higher terrain by midweek.

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...Thompson
NEAR TERM...Thompson/JLV
SHORT TERM...Thompson
LONG TERM...Frugis
AVIATION...JLV
FIRE WEATHER...Speciale
HYDROLOGY...Speciale

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Special Weather Statement
National Weather Service Albany NY
639 PM EST Sun Nov 15 2020

NYZ033-038>040-082-160030-
Southern Fulton-Hamilton-Southern Herkimer-Northern
Fulton-Montgomery-
639 PM EST Sun Nov 15 2020

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT SOUTHWESTERN
HAMILTON...WESTERN FULTON...SOUTHERN HERKIMER AND WESTERN MONTGOMERY
COUNTIES...

At 639 PM EST, radar indicated strong thunderstorms were located
along a line extending from New York Mills to near South Brookfield
to near Bainbridge. Movement was east at 50 mph.

Winds in excess of 40 mph are possible with these storms.

These storms will be near...
  Ilion, Frankfort and West Winfield around 650 PM EST.
  Herkimer, Newport, Poland and Cold Brook around 655 PM EST.
  Middleville and Jordanville around 700 PM EST.
  Dolgeville around 710 PM EST.
  Stratford around 715 PM EST.
  Fort Plain, St. Johnsville and Ames around 720 PM EST.
  Canajoharie around 725 PM EST.
  Ephratah around 730 PM EST.

Other locations impacted by these storms include Ingham Mills,
Spinnerville, Cedar Lake, Farrel Corner, Countryman, Whitehouse,
South Ilion, Mindenville, Kelhi Corners and Chepachet.
This includes Interstate 90 between exits 29 and 30.

LAT...LON 4322 7507 4324 7507 4323 7510 4325 7515
      4327 7516 4334 7491 4334 7487 4336 7486
      4348 7441 4296 7438 4278 7449 4281 7456
      4283 7465 4290 7488 4283 7491 4291 7510
      4286 7514 4286 7521 4292 7520 4305 7522
TIME...MOT...LOC 2339Z 253DEG 42KT 4309 7527 4277 7527 4231 7555

DBT

Special Weather Statement
National Weather Service Albany NY
645 PM EST Sun Nov 15 2020

NYZ032-033-038-160045-
Northern Herkimer-Hamilton-Southern Herkimer-
645 PM EST Sun Nov 15 2020

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT HAMILTON AND NORTHERN
HERKIMER COUNTIES...

At 645 PM EST, radar indicated strong thunderstorms were located
along a line extending from 9 miles south of Fowler to New London.
Movement was east at 45 mph.

Wind gusts up to 50 mph are possible with these storms.

These storms will be near...
  Hinckley around 720 PM EST.
  Ohio around 730 PM EST.

Other locations impacted by these storms include Eagle Nest, Little
Rapids, Beaver River, Nobleboro, Perkins Clearing, Minnehaha, Carter
Station, Quaker Beach, First Lake and Deerland.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 4344 7441 4325 7515 4330 7515 4335 7508
      4410 7517 4405 7505 4412 7429
TIME...MOT...LOC 2345Z 267DEG 39KT 4414 7536 4321 7562

DBT