Scientific Forecaster Discussion
fxus61 kbgm 200816
Area forecast discussion
National Weather Service Binghamton New York
416 am EDT Tue Aug 20 2019
high pressure briefly slides through the region today, with
fair conditions other than early morning valley fog. However,
a system will affect the region tonight into especially
Wednesday with showers and thunderstorms becoming likely. A
cold front will pass Thursday with scattered showers, which
will usher in quiet and cooler conditions through the weekend.
Near term /through Wednesday/...
400 am update...
main concern is for potential strong to severe thunderstorms
Wednesday, which may also include locally heavy rainfall.
Before we get to busier weather, today will actually be a fairly
quiet day as high pressure skims through the area. It is
drifting overhead this morning, with light to calm wind along
with mostly clear sky. This good radiational cooling set up
along with moisture of our recent wet pattern is producing
fog in typical valleys of the twin tiers to western Catskills,
with fingers of it sneaking up towards Cortland Cooperstown and
Hamilton as well as southern tips of The Finger lakes.
After the fog Burns off this morning, a mostly sunny is expected
with highs mainly in the 80s. However, light southwesterly
return flow will get going on the backside of the departing
high, allowing increasing moisture to start edging into the area
late today through this evening. A few showers or an isolated
thunderstorm cannot be ruled out in parts of northeast PA to
perhaps the central southern tier of New York this evening.
Flow aloft also skews southwesterly tonight, with small
ripples/shortwaves embedded within. Moisture will continue to
creep up, along with a bit of instability aloft. This will
contribute to a small yet increasing chance of showers and
embedded thunder overnight with lows mostly mid to upper 60s.
Wednesday appears to be an active yet complicated day. The
biggest question will be how much surface heating can be
realized, because there will be multiple waves moving through
the region. That being said, there are several other factors
nudging in the direction severe weather potential. An elevated
mixed layer will advect into the region aloft, presenting decent
mid level lapse rates along with upper level divergence. Thus,
convection will not be entirely reliant on surface-based
heating. At least modest deep layer shear of 25-35 knots is also
apparent in the models, with 0-1 km helicity also increasing
with time to above 100 m2/s2 especially east of Interstate 81.
Weak yet existent 500mb height falls could also help a bit with
initiation, and meanwhile precipitable water values of 1.6-1.9
inches is likely; though the models vary on this. The end
result is an expectation for clusters of convection over the
region, including mesoscale to storm scale interactions.
This will not be like a squall along a boundary with well-
advertised timing; at this point it is difficult to determine
timing and locations. But after morning showers and embedded
thunder, the environment will indeed become more supportive of
strong to severe cells in the afternoon with damaging winds,
some hail, and perhaps even rotation/a few supercells for an
isolated tornado threat. There could also be localized urban
and small stream flooding issues where cell interactions and
overlaps prolong downpours. Surface heating will ultimately
be the biggest determining factor for the actual coverage of
the storms, but at least scattered convection can be expected.
The Storm Prediction Center thus includes most of the area in a
slight risk of severe thunderstorms for Wednesday.
Short term /Wednesday night through Thursday night/...
There will likely be showers and thunderstorms around the region
Wednesday evening as a surface front progresses from west to east
across the area. Highest pops look to be from about I-81 east in the
evening. A few storms could still be strong into the early evening
hours, see the above near term section for more details on this
potential. Overnight, the area could still see some isolated shower
or thunderstorm activity but winds turn west-northwest toward
daybreak ushering in a more stable air mass. Upper level trough
remains over the region through the day Thursday, but drier air
moves in on the increasing northwest flow. Current guidance shows a
sharp moisture gradient, with higher dew points and instability
hanging on approximately southeast of Delhi to Towanda during the
morning...then nudging even a bit further south later in the
day...mainly from Monticello to Scranton. Continued to show a chance
of showers and a slight chance of thunderstorms in this area. If
current trends hold it should be mainly dry from Binghamton north
and west much of the day Thursday. There are some indications that
the surface front may stall or only very slowly drift south Thursday
night as a wave rides along it. This could keep at least a low end
chance for more showers in the forecast across NE PA. However, some
of the guidance, such as the 00z GFS has the front pushing east and
high pressure already building in later Thursday night...so
uncertainty remains for this period.
Wednesday night will be mild and humid with lows well into the 60s,
Thursday will have highs 75-80 for central NY, with low to mid-80s
across NE PA. Turning much cooler Thursday night with lows in the
Long term /Friday through Tuesday/...
High pressure and a dry northerly flow build in behind the front for
both Friday and Saturday. The area will be under a large upper level
trough, which slowly pulls east and exits by Saturday. Surface front
will stall well south of the area and continue to be the focus of
showers and storms across far southern PA and the mid-Atlantic into
the weekend. Our forecast area will be dry, partly to mostly sunny
with cooler than average temperatures for this period. Expect low
humidity, with highs 68-75 Friday...and 70-78 Saturday. Early fall
like temperatures expected overnight, 45-55 degrees. There will also
be a brisk north-northwest breezy both Friday and Saturday 8-15 mph,
with a few higher gusts possible.
Sunday and monday: model guidance is in good agreement that an upper
level ridge will build over the region as the surface highs shifts
east into New England. Our area will have a southeast, then
southerly return flow around this high. The dry and mostly
sunny/clear weather continues right into Monday. Temperatures and
humidity gradually rise. Look for highs in the mid-70s to lower 80s,
and still comfortable overnight lows in the 50s.
By next Tuesday, upper level ridge remains in place but moisture and
instability continue to increase. This could lead to a chance of
showers and/or thunderstorms. Still a good deal of uncertainty.
Temperatures reach back into the 80s for most locations.
Aviation /08z Tuesday through Saturday/...
passing high pressure early this morning, with a mostly clear
sky yet also moisture from recent rainfall of the last few days,
will lead to fog formation definitely for kelm but also
reaching to kith-kavp-kbgm terminals towards dawn. Kelm is
likely to hit Airport minimums at times especially 09z-12z, with
kith-kavp-kbgm expected to achieve at least down to IFR if not
briefly worse. While significant restrictions are not expected
for ksyr-krme, watch for amendments at krme since at least mist
will try to form in the Mohawk Valley and it could be touchy as
to whether IFR-or-worse could be reached. Any fog mixes out
between 12z-14z, leaving VFR conditions for the rest of the taf
period. The small caveat, is a slight chance of a shower or
thunderstorm this evening at kavp. Winds will be variable to
light southwest 5 knots or less today, before backing south to
southeast this evening.
Late Tuesday night through Wednesday night...restrictions
possible in showers and thunderstorms, especially Wednesday
Thursday...scattered showers and possible brief restrictions as
a cold front passes, otherwise VFR.
Thursday night through Sunday...VFR, except late night/early
morning fog possible at kelm over the weekend.