Area Forecast Discussion
Issued by NWS Binghamton, NY

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FXUS61 KBGM 281751
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
1251 PM EST Tue Feb 28 2017

.SYNOPSIS...
Flow out of the south to southwest willpush temperatures well
above normal today, and even more so tonight and Wednesday. A
strong storm system will bring showers and thunderstorms across
New York and Pennsylvania Wednesday. Some of those storms could
contain strong gusty winds and downpours. Colder air will follow
for the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
1145 AM update...Getting a good amount of sun this morning
resulting in temperatures rising quickly. Asjuested the grids
for more sun and increased temperatures in the short term. Also,
12Z models showing little chance of showers through at least 00Z
so have backed off on pops for the remainder of the day and into
the evening.

9 am update...
Just minor changes. Clouds remaining across most of the area but
showers have moved out. Another batch is inbound for later today
from Ohio.

430 AM Update...
Light precipitation early this morning could result in spotty
ice in isolated parts of Central New York, otherwise this period
will feature temperatures surging well above normal.

High pressure is located offshore over the Atlantic, and
southerly return flow around it is resulting in warm air
advection. However, temperatures earlier tonight did manage to
drop to near freezing in some pockets of Central New York.
Meanwhile, left exit region of jet aloft, in tandem with warm
air advection in the midlevels, is producing very light
precipitation in Central New York early this morning. Coverage
on radar looks more extensive than it really is, due to both
bright-banding and virga on the periphery. The strip of light
precipitation extends from about Penn Yan to Ithaca to Cortland
to Norwich and Cooperstown. Though most locations are above
freezing, the few spots around 32 degrees could have patchy ice.

Later this morning we get into the unfavorable right exit region
of the jet, and the resulting forced descent will tend to
suppress activity. There will still be a chance of rain showers
but most of the time conditions will be dry. Strong warm air
advection will likely send temperatures not just well above
normal but also at least slightly above model guidance as
typically happens in southwest flow during late winter-early
spring. We are expecting mainly mid 50s to lower 60s for highs.

Pressure gradient will increase tonight as strong low pressure
ejects from Central Plains into the southwestern Great Lakes
region. Southerly winds will increase accordingly and become
quite breezy at higher elevations, while holding temperatures
from falling below upper 40s-mid 50s for most locations.
Embedded waves within the southwest flow aloft will result in
scattered showers overnight, though with some instability in the
mid levels there could be a rumble or two.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
445 AM Update...
Main concern is for another threat of severe thunderstorms
including potential for damaging winds and heavy downpours. As
the saying goes, March comes in like a lion, though some could
argue the lion actually arrived a few days early this past
weekend.

We are forecasting record high temperatures for the first day of
the month, which is part of what will provide fuel for potential
severe thunderstorms Wednesday afternoon-evening. Widespread mid
60s to lower 70s appears likely, surpassing daily records of 63
degrees in Syracuse, 60 degrees in Binghamton, and 68 degrees in
Scranton (Avoca). The Binghamton and Avoca records were set in
1972, and the Syracuse one is front 1954.

The Storm Prediction Center has upgraded Northeast PA and
Southern Tier-Catskills NY into a Slight Risk for Severe
Thunderstorms Wednesday, with at least Marginal Risk further
north. There is uncertainty in the details as to whether or not
clouds will break for additional heating, between a morning
wave of showers-embedded thunder, and afternoon-evening
thunderstorms along pre-frontal trough and/or cold front.
However, it has become apparent that even if clouds stay quite
persistent, the atmosphere will become unstable. Model soundings
vary from a few hundred J/KG for Convective Available Potential
Energy (CAPE) to almost 1000 J/KG; in almost all cases adequate
for at least scattered thunderstorms. The tougher part is
whether smaller clusters of showers-thunder will tend to break
up organization. Hodographs are not as curved as the event we
had Saturday, yet there is still some. Instead of strong
southerly flow, it is more of a southwesterly direction, yet
speed shear is again at very strong values. Models indicate that
most of the 2km-6km layer will be southwesterly at 60-80 knots.
Damaging winds will be the main concern with any storms
Wednesday afternoon-evening, whether organized as a primary line
or in segments. That being said, 0-1km helicity values are
still in the 150-300 m2/s2 range and thus a tornado or two also
cannot be ruled out.

Another concern is potential for flash flooding. Flash flood
guidance (that is, how much rain it would take in an hour to
cause flash flooding to begin) is still very low for portions
of South Central NY and Northeast PA due to the recent snow
melt and also the 1-1.5 inches of rain this area received on
Saturday. So, with saturated soils, a large portion of any
additional heavy rainfall will become runoff. Overall rain
amounts do not look especially high, and storms will be
progressive, yet whatever does fall could come quick and heavy;
possibly to the point of causing water problems. Precipitable
water values are forecast to reach about 1.2 inches, or between
3 and 4 standard deviations above normal. This is actually
slightly higher than the event we just had last weekend, yet as
mentioned, thunderstorms will be more progressive (shorter-
lasting) as well.

After the front moves through Wednesday night, temperatures
will drop sharply with showers-storms possibly ending as wet snow
showers. There will also be strong, gusty winds behind the
front on the synoptic scale due to strong pressure gradient on
the backside of departing low. Temperatures bottom out in the
upper 20s to mid 30s Wednesday night.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
The northeastern U.S. still looks to be under a large-scale
trough for the end of the week into next weekend. This means
fairly cold temperatures (highs mainly in the 20`s and 30`s),
along with frequent chances of light snow or flurries,
especially later Thursday night into Friday, when a clipper type
low is anticipated to track across southern PA or the Delmarva
region.

By later Saturday, a ridge of high pressure is expected to build
across NY and PA, to bring a brief period of dry weather. Then,
from later Sunday into early next week, an approaching warm
front will ultimately bring milder temperatures, along with
potentially some rain showers.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...

Mainly clear skies this afternoon will continue into the evening
with southerly winds around 10 kts or so. Tonight, moisture
increases slowly bring gradually lower ceilings. MVFR decks Will
develop after 06Z along with patchy light rain. Heavier rain
will move in after 12Z as a surface trof and a series of upper
waves push through. Expect lower ceilings at or near IFR levels
and MVFR visibilities in rain.

OUTLOOK...

Wednesday Night...Occasional restrictions likely in rain
showers and snow showers.

Thursday/Friday...Possible restrictions in snow showers.

Saturday...VFR.

Sunday...Restrictions in rain and snow showers.

&&

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

&&

$$
SYNOPSIS...DGM/MDP/TAC
NEAR TERM...DGM/MDP/TAC
SHORT TERM...MDP
LONG TERM...MLJ
AVIATION...DGM


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