Hail and Damaging Winds in New York, June 21, 2021

Area Forecast Discussion
National Weather Service Binghamton NY
151 PM EDT Mon Jun 21 2021

.SYNOPSIS...
A strong cold front will run into very warm and humid conditions
today to yield scattered severe thunderstorms this afternoon
and evening. Damaging winds will be the main threat, but large
hail and locally heavy rainfall may also occur. Lingering
showers exit Tuesday, with much cooler and drier air overtaking
the region for midweek.

&&

.NEAR TERM /THROUGH TUESDAY/...
130 PM Update...
Severe Thunderstorm Watches have been issued for most of Central
NY. An additional watch will be possible for Northeast PA-
Southern Catskills later this afternoon.

1115 AM Update...
As expected, skies have cleared and a mix of sun and clouds is
present across the majority of the area. This will enhance the
instability heading into this afternoon. The area is currently
capped (currently preventing any convective development) but
expecting this to break this afternoon, allowing for explosive
convective development. Still expecting some isolated to
scattered cells to develop ahead of the main line of storms
after 1PM or so. The main line of storms is still expected to
move through the area from west to east during the mid-late
afternoon into this evening.

With this update, made minor adjustments to PoPs to account for
a slightly faster movement of this line. Expectations for the
storms remain the same though: damaging winds, large hail,
locally heavy rainfall, and possibly a few tornadoes all remain
possible. Pay close attention to the weather and be prepared to
seek shelter if necessary. Have multiple ways of getting weather
information/receiving warnings.

720 AM Update...
Line of thunderstorms with 30-40 mph winds on its southern end,
skimmed through the northern Finger Lakes-western NY Thruway but
is finally running out of gas. The northern end had more to work
with and is still carrying across eastern Lake Ontario.

Based on latest model guidance, timing for the scattered severe
storms this afternoon was adjusted later by roughly an hour.
Expectations though remain the same; it will be a busy day.

Previous discussion...
We are anticipating a severe weather event this afternoon
through early evening, with scattered thunderstorms containing
damaging winds. Large hail and locally heavy rainfall may also
occur, and an isolated tornado cannot be ruled out.

Despite it being nighttime, plenty of instability already exists
aloft, as evidenced by weak shortwaves popping small clusters of
nocturnal convection. Increasing warm air advection aloft will
produce thermal capping to shove these cells mainly north of our
area by mid morning. However, this will also allow sunshine and
thus heating to occur. The very warm air mass will quickly be
realized at the surface with temperatures well into the 80s to
around 90 degrees by shortly after noon, and south-southwest
winds will pick up considerably in response to the approaching
cold front of an anomalously strong low moving into Quebec this
afternoon. With dewpoints into the upper 60s, heat index values
will boost to between 90-95 degrees at lower elevations. This is
pretty close to Heat Advisory criteria, at least for Central NY,
but we opted to not hoist it due to how briefly it will touch
95 degrees Heat Index if at all, before convection moves in.
Also there will be a pretty good breeze instead of just being
stagnant.

Though a thermal cap initially exists, 500mb height falls will
get underway this afternoon as a significant upper trough digs
into the western to central Great Lakes. The resultant
steepening of lapse rates aloft, as well as heat and humidity in
the low levels, will break the cap to cause robust convection
this afternoon.

0-6km bulk shear values appear likely to reach 40 knots, plenty
high enough to support organized severe convection given the
degree of instability which models have converged to be likely
at least in the 2000-2500 J/kg range for Convective Available
Potential Energy (CAPE). In addition, 0-1km helicity values are
likely to reach at least 100-150 m2/s2 as well as 0-3km helicity
of 150-225 m2/s2 as per the latest High Resolution Ensemble
Forecast (HREF). Lifting Condensation Levels (LCL) may be a bit
elevated, especially towards Northeast PA, but the significant
shear today suggests that an isolated tornado or two cannot be
ruled out. At a minimum, we will get rotating
updrafts/mesocyclones, with the resultant possible cores of
large hail and severe downdrafts during initial multi-cells and
supercells in early to mid afternoon. As time wears on, the
forcing provided by the front should congeal convection into a
linear mode with damaging winds becoming the primary threat late
afternoon-early evening.

With warm cloud depths beyond 10 kft agl, and precipitable water
(Pwat) values at least approaching 2 inches, locally heavy
rainfall will also be a concern. Convection will tend to be
progressive enough to prevent flash flooding on an organized
scale. However, locations that receive 2-3 hits from multiple
cells, such as from initial multicells ahead of what becomes
the primary line, could end up with excessive rain and thus
isolated flooding problems.

Finally, it should be noted that the storms today are likely to
produce frequent cloud-to-ground lightning, due to the more-
than-usual convective energy that will extend beyond 40 kft in
terms of equilibrium level.

After the storms exit in the evening, northwesterly winds will
advect in much cooler air. However, the right entrance region of
a strong jet will provide forced ascent aloft, with additional
waves of showers late tonight into Tuesday morning. That said,
those rains will be considerably lighter and should not cause
issues. Temperatures will settle to between 50-60 degrees by
dawn Tuesday.

Lingering showers end west to east on Tuesday, yet with
persistent clouds and chilly northwest wind. Temperatures will
not move a whole lot from the morning readings, with highs
mostly in the 60s. Some late day sun may creep in from the west.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
Quiet weather with a gradual warming trend for the short term, as an
area of high pressure builds over the region.

On Wednesday, there will be a departing upper level trough over the
region. 1000-500mb thicknesses will still be rather low, starting
out between 546-552dm in the morning, with warm air advection slowly
arriving by afternoon. Otherwise, at this time guidance is indicating
mostly sunny skies with only a slight west-northwest breeze 7-15
mph. Below average temperatures expected, after starting out
very chilly in the upper 30s to mid-40s early, it'll recover to
between 70-75 by afternoon.

Wednesday Night: Mostly clear, quiet and cool with light winds and
high pressure directly overhead. Cannot rule out some patchy valley
fog. but not enough confidence to put in the forecast grids just
yet. Overnight lows dip down into the mid-40s to lower 50s.

Thursday: Our weather will be dominated by the surface ridge of high
pressure once again, as it slowly slides of the New England coast.
Gradually increasing southerly return flow, with mostly sunny skies
expected. Temperatures warm back up to seasonable levels, with highs
in the upper 70s to lower 80s. Dew points remain low, in the upper
40s to low 50s, so very comfortable humidity levels.

Thursday night: Another quiet night weatherwise. Surface ridging
continues to nudge in from New England, which will keep mostly clear
conditions over our CWA. Not as cool, but still comfortable with
overnight lows mainly in the 50s. Light southeast winds 5-10 mph.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Starting off mainly quiet on Friday, but an upper level trough
slowly approaches from the west late in the day. Overall, expecting
partly sunny and seasonable weather, but again cannot rule out a
stray late day shower or storm. Chances for scattered showers
gradually increase Friday night, as a surface low tracks into the
central Great Lakes and St. Lawrence Valley region. Warm overnight
lows expected considering the increased clouds and southerly
flow...expect low to mid-60s overnight.

The weather pattern then looks to remain active for the weekend and
right into early next week. Our area will be caught in a deep
southwest flow with ample moisture (1.75"+ PWATS) between a slow
approaching upper trough and a retrograding Atlantic ridge.
Instability will increase, bringing likely PoPs for showers and
scattered t'storms Saturday, Sunday and Monday afternoon. No
particular day looks like a washout at this time. A few storms
may be better organize heading into Sunday and Monday, but this
will depend on the trough position and amount of deep shear
available. Becoming more humid as dew points rise into the 60s,
along with seasonably warm temperatures. Expect daytime highs
between 80-85, with muggy overnight lows in the 60s.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Mainly VFR conditions will exist this afternoon. However,
thunderstorms are expected this afternoon; some may be severe
with strong winds and hail. Right now included thunder in 2 hour
long TEMPO groups during the period where highest confidence is.
That being said, be on the lookout for potential amendments to
further refine the timing or if storms head towards a terminal
outside of the TEMPO window. Behind the showers and
thunderstorms ceilings are expected to lower to MVFR and perhaps
Fuel Alternate this evening/overnight. These ceiling
restrictions may persist through Tuesday morning before
gradually improving Tuesday afternoon.

Outlook...

Tuesday afternoon through Friday...Mainly VFR, though valley
fog is probable for late nights-early mornings at KELM.

Saturday...Restrictions possible in scattered showers and
thunderstorms.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.

&&

SYNOPSIS...MDP
NEAR TERM...BJG/MDP
SHORT TERM...MJM
LONG TERM...MJM
AVIATION...BJG

Hazardous Weather Outlook
National Weather Service Binghamton NY
118 PM EDT Mon Jun 21 2021

NYZ046-057-062-PAZ038>040-043-044-047-048-072-221730-
Otsego-Delaware-Sullivan-Bradford-Susquehanna-Northern Wayne-Wyoming-
Lackawanna-Luzerne-Pike-Southern Wayne-
118 PM EDT Mon Jun 21 2021

This Hazardous Weather Outlook is for central New York and
northeast Pennsylvania.

.DAY ONE...This afternoon and tonight.

...SCATTERED SEVERE THUNDERSTORMS EXPECTED TODAY...

A more organized round of scattered severe thunderstorms is expected
late this afternoon through evening. Main threats will be damaging
winds, large hail, and frequent lightning. Locally heavy rainfall is
also possible, and an isolated tornado cannot be ruled out.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed. Please relay any
information about severe weather to the NWS while following local,
state and CDC guidelines.

NYZ015>017-022-023-221730-
Yates-Seneca-Southern Cayuga-Steuben-Schuyler-
118 PM EDT Mon Jun 21 2021

...SEVERE THUNDERSTORM WATCH 299 IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

This Hazardous Weather Outlook is for central New York.

.DAY ONE...This afternoon and 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...Tuesday through Sunday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed. Please relay any
information about severe weather to the NWS while following local,
state and CDC guidelines.

NYZ009-018-024-025-036-037-044-045-055-056-221730-
Northern Oneida-Onondaga-Chemung-Tompkins-Madison-Southern Oneida-
Cortland-Chenango-Tioga-Broome-
118 PM EDT Mon Jun 21 2021

...SEVERE THUNDERSTORM WATCH 300 IN EFFECT UNTIL 9 PM EDT THIS
EVENING...

This Hazardous Weather Outlook is for central New York.

.DAY ONE...This afternoon and 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...Tuesday through Sunday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed. Please relay any
information about severe weather to the NWS while following local,
state and CDC guidelines.

Special Weather Statement
National Weather Service Binghamton NY
145 PM EDT Mon Jun 21 2021

NYZ009-211815-
Northern Oneida-
145 PM EDT Mon Jun 21 2021

...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN ONEIDA COUNTY...

At 145 PM EDT, a strong thunderstorm was located 9 miles southeast of
Pulaski, or 15 miles southeast of Sandy Island Beach State Park,
moving northeast at 35 mph.

Wind gusts up to 50 mph and dime size hail are possible with this
storm.

Locations impacted include...
Florence.

LAT...LON 4348 7577 4346 7569 4345 7566 4339 7586
      4347 7582 4348 7581
TIME...MOT...LOC 1745Z 241DEG 30KT 4345 7602

DJP

Special Weather Statement
National Weather Service Binghamton NY
158 PM EDT Mon Jun 21 2021

NYZ018-211830-
Onondaga-
158 PM EDT Mon Jun 21 2021

...A STRONG THUNDERSTORM WILL AFFECT CENTRAL ONONDAGA COUNTY...

At 158 PM EDT, a strong thunderstorm was located over Marcellus, or
11 miles west of Syracuse, moving northeast at 25 mph.

Winds in excess of 40 mph and half inch hail are possible with this
storm.

Locations impacted include...
Onondaga, Syracuse, Cicero, De Witt, North Syracuse, Solvay, Manlius,
Fayetteville, Minoa and East Syracuse.

LAT...LON 4322 7608 4320 7608 4320 7606 4299 7592
      4287 7638 4299 7647 4301 7646 4301 7648
      4303 7649 4322 7609
TIME...MOT...LOC 1758Z 243DEG 22KT 4298 7635

DJP

Special Weather Statement
National Weather Service Binghamton NY
200 PM EDT Mon Jun 21 2021

NYZ044-211830-
Cortland-
200 PM EDT Mon Jun 21 2021

...A STRONG THUNDERSTORM WILL AFFECT NORTHERN CORTLAND COUNTY...

At 200 PM EDT, a strong thunderstorm was located near Homer, or near
Cortland, moving northeast at 20 mph.

Winds in excess of 40 mph and half inch hail are possible with this
storm.

Locations impacted include...
Cortland, Homer, Preble, Scott, Truxton, Solon, McGraw, Cuyler, South
Cortland and East Homer.

LAT...LON 4270 7589 4268 7588 4263 7589 4254 7626
      4275 7627 4278 7623 4279 7602 4279 7595
TIME...MOT...LOC 1800Z 244DEG 18KT 4266 7624

DJP