Severe Thunderstorm Warning 115, NWS Albany, NY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
731 PM EDT Sat Aug 12 2023

.SYNOPSIS...
An upper-level disturbance and associated surface frontal
system will pass through the region through tonight, bringing
showers and thunderstorms. Stronger thunderstorms will be
capable of producing potentially damaging winds and hail.
Conditions improve Sunday into Monday as surface high pressure
slides into the region from the south and west. A widespread
soaking rain is then expected Monday night into Tuesday.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
* Severe Thunderstorm Watch issued for Greene, Columbia, Ulster,
  Dutchess and Litchfield Counties until 12 am.

* Isolated to scattered severe thunderstorms expected this
  evening. Damaging wind gusts and large hail are the main threats,
  but an isolated, spin-up tornado cannot be ruled out.

.UPDATE...Quick update for issuance of Severe Thunderstorm Watch
638 in effect until Midnight for Greene, Columbia, Ulster,
Dutchess and Litchfield Counties. This is where the best overlap
of instability and shear is located. The special 20Z sounding
from SUNY Albany revealed rather paltry instability (577 J/Kg
CAPE) locally, thus limiting the watch to areas south of
Albany. Wind profile from the sounding does show veering winds
from the surface up to 700 mb, with 0-3 km shear of 20 kt.
Rotating/severe storms moving through Ulster County at this
time. Will continue to monitor this area.

.PREV DISCUSSION[0407]...Instability: Limited in eastern NY and
western New England as NY Mesonet profilers showing less than
1000 j/kg in eastern NY but 1000+ j/kg central and western NY.
Sector of greatest instability shifting east from just north of
the NY/PA border and suggests the strongest storms will also
shift through the eastern Catskills, mid Hudson Valley, very
southern Berkshires and Litchfield Hills. Midlevel lapse rates
are meager, but surface based instability will be enough for
isolated to scattered severe potential in southern parts of the
area.

Shear: NY State Mesonet profilers showing 0-1Km storm relative
helicity and 0-3Km helicity of 150 m2/sec2 or less, not very
supportive of much rotation in thunderstorms but if instability
can increase, there could be a spin up tornado. VAD Wind
Profiles from radars from OH into western PA and NY show better
shear with storm relative helicity above 150 m2/sec2, and the
increasing southwesterly boundary layer winds that are building
east through our region may enhance chances for rotating
thunderstorms over southern areas this evening.

CAM/Mesoscale model trends: Increasing consensus for scattered
thunderstorms along and north of I-90 but the best instability
and shear may be south of I-90 as clusters and segments in
central/southern NY combine into a more solid line or band of
storms that tracks through southern areas through this evening
with the severe weather potential and isolated urban and small
stream flooding and maybe flash flooding.

The storms may be trending toward the region of highest low
level equivalent potential temperature in PA/NJ, which again,
favors the best chances for severe thunderstorms and isolated
flooding in southern areas. The cluster in far western NY/PA
could track through southern areas between midnight and
daybreak Sunday. There should be partial clearing toward
daybreak but the low level wind shift may be delayed until just
after daybreak. Light winds and wet ground could promote some
patchy fog once the rain exits and where there is some clearing.
Lows in the 60s and around 60 in higher terrain.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Drying and clearing through SUnday and there could be some gusty
west to northwest winds during the afternoon. Highs Sunday in
the upper 70s to lower 80s with a few mid 80s southern areas and
cooler in higher terrain.

The next organized upper energy and increasing warm advection
ahead of it begins to approach Monday with increasing clouds. It
should be dry through the day with highs around 80 to mid 80s
and cooler in higher terrain.

Rapidly increasing moisture and boundary layer flow will
support increasing coverage of showers and isolated
thunderstorms Monday night. There could be some locally heavy
rain and after a short lull in the action Tuesday morning,
additional showers and storms expected Tuesday afternoon.
Limited sunshine will limit highs to the mid 70s to near 80 and
cooler in higher elevations. The severe weather threat is
limited due to limited instability but shear will be
considerable with increasing boundary layer winds, so a few
storms could approach marginal severe levels. There will also be
locally heavy rain and possible isolated to scattered nuisance
urban and small stream flooding.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
The period starts out Tue evening with a weak area of low pressure
along a frontal system moving east into New England. The upper level
trough is forecast to be positively tilted, so the system should be
progressive. Will mention just a slight to low chance of a few
leftover showers Tue evening, then drying overnight.

Dry and seasonable conditions then expected Wed through Thu, as high
pressure builds east across the region. Thu looks slightly warmer
than Wed, as a southerly flow develops around the periphery of the
high as it departs off the New England coast.

The next chance for showers/T-storms arrives late Thu night into
Fri, as a possible upper level trough/closed upper low approaches
from the Great Lakes and SE Canada. There are model differences this
far out, with the CMC slower than the ECMWF, but non-existent in the
12Z GFS. So for now will go with NBM and mention chance PoPs through
Fri evening until this potential system comes into better focus.
Temperatures look to be near to slightly above normal through
Sat.

&&

.AVIATION /23Z SATURDAY THROUGH THURSDAY/...
Isolated thunderstorm near KGFL should exit by 01Z. Better
coverage of thunderstorms in northern and central NY will move
east but weaken and become more scattered through this evening
and night as the storm move toward KGFL and KALB. Acknowledging
VCSH at KGFL, KALB and KPSF through about 09Z. Any scattered
showers or storms should exit after 09Z but some low clouds,
ceilings around 1000 feet, and some MVFR/IFR visibilities
expected after the rain exits, through about 14Z.

KPOU has some thunderstorms nearby and including intervals of
IFR conditions in thunderstorms through 02Z. Wind gusts to 35Kt
are possible in the storms as well. After 02Z, other weaker
showers and storms will track east from central NY and decrease
in coverage through the night. Including VCSH at KPOU
through about  09Z until the rain exits, and some low clouds
and fog possible through about 14Z. After about 14Z, low clouds
break up and lift and VFR conditions are expected through the
rest of Sunday morning and afternoon.

Winds will be south to southwest at 10 Kt or less this evening,
except gusts to 35 Kt or more possible in thunderstorms. Winds
shift to west and northwest at less than 10 Kt after 12Z-14Z.
West winds around 10 Kt continue through the rest of Sunday
morning and afternoon.

Outlook...

Sunday Night: No Operational Impact. NO SIG WX.
Monday: No Operational Impact. NO SIG WX.
Monday Night: High Operational Impact. Likely SHRA...TSRA.
Tuesday: High Operational Impact. Likely SHRA...TSRA.
Tuesday Night: Low Operational Impact. Slight Chance of SHRA.
Wednesday: No Operational Impact. NO SIG WX.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.

&&

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

&&

SYNOPSIS...NAS
NEAR TERM...NAS/JPV
SHORT TERM...NAS
LONG TERM...JPV
AVIATION...NAS

Hazardous Weather Outlook
National Weather Service Albany NY
652 PM EDT Sat Aug 12 2023

CTZ001-013-NYZ058>061-063>066-131100-
Northern Litchfield-Southern Litchfield-Western Greene-
Eastern Greene-Western Columbia-Eastern Columbia-Western Ulster-
Eastern Ulster-Western Dutchess-Eastern Dutchess-
652 PM EDT Sat Aug 12 2023

...SEVERE THUNDERSTORM WATCH 638 IN EFFECT UNTIL MIDNIGHT EDT
TONIGHT...

This Hazardous Weather Outlook is for northwestern Connecticut and
east central New York.

.DAY ONE...Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Severe Thunderstorm Watch.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

The chance for thunderstorms returns late Monday night through
Tuesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is requested through this evening.

MAZ001-025-NYZ032-033-038>043-047>054-082>084-VTZ013>015-131100-
Northern Berkshire-Southern Berkshire-Northern Herkimer-Hamilton-
Southern Herkimer-Southern Fulton-Montgomery-Northern Saratoga-
Northern Warren-Northern Washington-Schoharie-Western Schenectady-
Eastern Schenectady-Southern Saratoga-Western Albany-Eastern Albany-
Western Rensselaer-Eastern Rensselaer-Northern Fulton-
Southeast Warren-Southern Washington-Bennington-Western Windham-
Eastern Windham-
652 PM EDT Sat Aug 12 2023

This Hazardous Weather Outlook is for western Massachusetts, east
central New York, eastern New York and southern Vermont.

.DAY ONE...Tonight.

Isolated to scattered severe thunderstorms expected this evening.
The main threats will be damaging wind gusts and large hail, however
an isolated tornado can not be ruled out. In addition, storms will
be capable of locally heavy rainfall which could lead to some urban,
low lying and poor drainage flooding with isolated to scattered
flash flooding possible.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

The chance for thunderstorms returns late Monday night through
Tuesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed.

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