Severe Thunderstorm Warning 67, NWS Binghamton, NY

Area Forecast Discussion
National Weather Service Binghamton NY
1007 AM EDT Tue Jun 27 2017

.SYNOPSIS...
Today will remain cool and unsettled, as another upper level
disturbance, brings the likelihood of showers and
thunderstorms, especially over central New York. By Wednesday,
drier and warmer weather is expected, as high pressure builds
over the region.

&&

.NEAR TERM /THROUGH WEDNESDAY/...

1005 AM Update...Upper low is advancing east slowly into western
NY. Band of showers ahead of the low is moving east of
I81...followed by a dry area. More showers and isolated thunder
will develop this afternoon as the low passes by. Some gusty
winds and small hail is possible. Grid updates this morning
included adjusted timing on showers and drier areas, and temps,
especially in areas where clouds and rain have kept them lower
than forecast. Previous discussion continues below.

3 am update... Earlier showers have pushed eastward into the
Hudson Valley at this time, with patchy clouds and areas of fog
left in its wake. Fog could be locally dense in some of our
river valleys prior to daybreak.

The next system to impact the region later today will be a
vigorous short-wave/compact upper low, well seen on satellite
imagery across eastern Michigan early this morning. As this
system translates eastward, so will its cold core aloft (mid-
level temperatures as low as -22 to -24C). This will result in
an expanding area of showers/embedded thunderstorms,
particularly over CNY, from later this morning through the late
afternoon hours. Model soundings later today show a well mixed
low-level environment once again over the forecast area, topped
by steep mid-level lapse rates (700-500 mb LR near 7C/km), some
dry air aloft, and fairly low freezing levels. These all point
to the possibility of gusty winds and hail with stronger
thunderstorms, so such verbiage will be added to our gridded
forecasts, and these threats will also be conveyed in our
hazardous weather outlook.

Temperatures will be cool again today, as we remain under the
influence of a chilly long-wave trough over eastern Canada and
the northeastern states. In fact, highs this afternoon will stay
in the 60s for many areas, with only the Wyoming/Lackawanna
Valleys of NEPA having a decent chance to eclipse 70 degrees.

Tonight, as the aforementioned short-wave/upper low lifts out to
the northeast, drier air and sinking motion will develop over
CNY/NEPA, leading to clearing skies over time. Only our far
northern zones (southern Tug Hill region) will retain a small
chance of showers, closer to the departing disturbance. Given
the probability of wet soils from recent rainfall and the onset
of good radiating conditions overnight, areas of fog seem like a
good bet in the usual twin tier river valleys. Lows by daybreak
should range from the upper 40s-mid 50s.

Wednesday looks like a pleasant early summer day, with a fair
amount of sunshine, and low humidity. Although readings will
certainly be warmer than the preceding couple of days,
Wednesday's highs will still be a bit below climatology for most
areas for late June, with temperatures ranging in the 70s.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
350 AM Update...
Main concern will be for return of thunderstorms Thursday
afternoon-evening, some of which could be strong to severe with
gusty winds and/or hail.

Wednesday night will be quiet, though clouds will be increasing
towards dawn ahead of the next system. It will probably be one
of those nights with a shallow surface inversion forming early
in the evening for the radiational cooling spots, yet
temperatures will hold milder for ridges and the Lake Plain.

Things turn interesting Thursday. Significant warm air
advection occurs, with southwesterly low level jet increasing
to 30-40 knots at 850mb. Associated warm front will be connected
to low pressure lifting from the upper Midwest, across the
Northern Great Lakes, to the Ontario-Quebec border. Meanwhile,
one or more shortwaves will zip through brisk westerly flow.
Precipitable water values will quickly get past 1.5 inches
Thursday afternoon through evening. Overall, enough coming
together for a likelihood of thunderstorms Thursday afternoon-
evening, especially in Central New York; with at least some
threat for strong winds due to a good amount shear through most
of the column as well as some dry air in the mid levels to
promote downdrafts. Hail also a threat due to amount of
Convective Available Potential Energy at hail growth
temperatures, and strong storm relative flow around or greater
than 50 knots at the equilibrium level. Mixed layer CAPE looks
probable to get past 1000 J/KG and perhaps 1500 J/KG in the Lake
Plain. 0-1km helicity values get into the hundreds, which is
worrisome, and points to potential for isolated supercells as
the warm front lifts east. Factors counting against a more
organized severe threat include mid level lapse rates that will
not be steep, and slight 500mb height rises instead of falls.
Also, while a jetmax or will travel across the region aloft, it
is unsure at this point if placement will be favorable or
perhaps even unfavorable for ascent. So the synoptic forcing
picture is unclear.

Though warm front will shift north of the area Thursday night,
shallow mesoscale boundaries could shove potential convection
further south across the area Thursday night, and thus we will
have to watch of the possibility of training storms and locally
heavy rainfall from elevated precipitable water values.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
350 AM Update...
Forecast adjusted towards latest multi-model blend. Same idea
holds true through the period; a busy weather pattern continues.
Though there will be dry intervals, it will be really tough to
go more than a day without showers-thunderstorms in the area.

Previous discussion...
SW flow aloft will prevail through most of the forecast period.
Multiple shortwaves are forecast to move across the region
through the period. This type of pattern will lead to an
unsettled weather, thus there is a chance for precip Friday
through Sunday. We may see another break in the pattern on
Monday which may bring us a couple days of dry weather.

It needs to be emphasized that although at least a chance of
showers/storms will be in the forecast through this period, any
all-day washouts look highly unlikely, with significant rain-
free periods, and convective chances greater coincident with
peak heating during the afternoon/early evening hours.

Friday-Monday, look for highs in the upper 70s-low 80s.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
For the most part, although VFR conditions will prevail today,
showers/embedded thunder will remain a possibility through mid-
late afternoon. A somewhat greater chance for this occurrence
will be for our CNY terminals, as opposed to KAVP. Although
brief restrictions are possible, we'll leave things as VFR at
this juncture. Also, we'll leave thunder out for now, although
we'll have to be vigilant of this possibility, especially during
the afternoon.

Lots of uncertainty with fog development later tonight, with
conflicting signals in the model data. For now, we've
introduced the idea of IFR-below alternate minimum restrictions
at KELM after 06z.

Generally W-SW winds will average 5-10 kt today. Any
showers/thunderstorms later today could bring brief gusty winds,
perhaps 25-35 kt. SW winds will diminish later tonight to 5 kt
or less.

Outlook...

Wednesday...Possible early morning fog at KELM, otherwise VFR.

Thursday through Saturday...At least periodic restrictions
anticipated in showers/thunderstorms.

&&

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

&&

SYNOPSIS...DGM/MLJ
NEAR TERM...DGM/MLJ
SHORT TERM...MDP
LONG TERM...KAH/MDP
AVIATION...MLJ/RRM

Hazardous Weather Outlook
National Weather Service Binghamton NY
357 AM EDT Tue Jun 27 2017

NYZ009-015>018-022>025-036-037-044>046-055>057-062-PAZ038>040-043-
044-047-048-072-280800-
Northern Oneida-Yates-Seneca-Southern Cayuga-Onondaga-Steuben-
Schuyler-Chemung-Tompkins-Madison-Southern Oneida-Cortland-Chenango-
Otsego-Tioga-Broome-Delaware-Sullivan-Bradford-Susquehanna-
Northern Wayne-Wyoming-Lackawanna-Luzerne-Pike-Southern Wayne-
357 AM EDT Tue Jun 27 2017

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

.DAY ONE...Today and Tonight.

Scattered thunderstorms are expected today, especially in Central New
York. Some storms could contain strong gusty winds and small hail.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

After a break Wednesday, a warm front will lift through the region
Thursday afternoon and evening with thunderstorms. There is a
potential for a few of these storms to be severe with damaging winds
and large hail. Monitor the forecast as this event gets closer.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Special Weather Statement
National Weather Service Binghamton NY
1143 AM EDT TUE JUN 27 2017

NYZ015>017-271630-
Southern Cayuga NY-Seneca NY-Yates NY-
1143 AM EDT TUE JUN 27 2017

...STRONG THUNDERSTORM WILL AFFECT...NORTHWESTERN SENECA...
NORTHEASTERN YATES AND WESTERN CAYUGA COUNTIES UNTIL 1230 PM EDT...

At 1141 AM EDT, Doppler radar was tracking a strong thunderstorm over
Kendaia, or 7 miles southeast of Geneva, moving east at 20 mph.

Nickel size hail and strong wind gusts will be possible with this
storm.

Locations impacted include...
Auburn, Seneca Falls, Waterloo, Romulus, Fayette, Fleming, Ledyard,
Port Byron, Union Springs and Aurora.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Heavy rainfall is also occurring with this storm, and may lead to
minor flooding. Do not drive your vehicle through flooded roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

If on or near a lake, get out of the water and move indoors or inside
a vehicle. Remember, lightning can strike out to 10 miles from the
parent thunderstorm. If you can hear thunder, you are close enough to
be struck by lightning. Move to safe shelter now! Do not be caught on
the water in a thunderstorm.

Persons in campgrounds should consider seeking sturdy shelter until
this storm passes.

&&

LAT...LON 4277 7697 4286 7698 4303 7669 4303 7656
      4269 7653 4267 7701 4276 7701
TIME...MOT...LOC 1541Z 252DEG 9KT 4278 7688

KAH