Area Forecast Discussion
Issued by NWS Binghamton, NY

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FXUS61 KBGM 201040

Area Forecast Discussion
National Weather Service Binghamton NY
640 AM EDT Thu Jul 20 2017

An approaching upper level disturbance, will bring some late
afternoon and evening showers and thunderstorms to the region.
Behind this system, weak high pressure builds in Friday, to
bring dry and seasonably warm weather. The weekend turns
unsettled again, as a frontal boundary in the vicinity, helps
to develop additional rounds of showers and thunderstorms.


420 am update... Locally dense river valley fog is forming again
early this morning, with otherwise just some patchy cloudiness
over CNY/NEPA. Fog should burn off by 8-9 am, with filtered
sunshine anticipated thereafter into early afternoon.

Convective potential later this afternoon into early evening
continues to look muddled, with conflicting signals in the model
fields. On the negative side, instability is questionable, with
some of our model guidance showing more destabilization over
western NY and PA, relative to our forecast area. However, some
of the models may be underdoing this, with a warm, humid
environment still in residence, along with the potential for an
elevated mixed layer (EML) in the mid-levels to advect in from
the WNW later today into this evening (this feature is evident
on GOES-16 channel 10 imagery over the upper Midwest at this
time). On the positive side, a short-wave embedded in the fast
flow aloft will be tracking through later today to provide some
synoptic support, and deep-layered shear should also be
available. Overall, there seems to be enough going for it to
justify likely probabilities for showers/thunder, from generally
about 4-9 pm. Isolated occurrences of strong winds and hail
cannot be ruled out, and thus we`ll retain this mention in our
Hazardous Weather Outlook.

Later tonight, any residual convection winds down, as sinking
motion develops behind the above mentioned short-wave. Wet
ground conditions and the likelihood of partial clearing
overnight should bring more valley fog.

Friday looks rain-free, with a drier air mass and subsidence
still in place, as weak high pressure builds across from
southern Ontario.


345 AM Update...
We are looking increasingly likely to get right back into a
busy weather pattern. Locally heavy rainfall could again become
a concern as well as potential for strong storms, especially
towards the second half of the weekend.

Ring-of-fire scenario will be setting up in the big picture,
with large dome of heat over most of the southern two-thirds of
the country, and a belt of westerlies across the northern U.S.
containing several disturbances/potential convective complexes
within the temperature gradient zone.

Friday night is quiet, but a warm frontal zone will be
positioned to our southwest. On Saturday, especially mid
afternoon into Saturday night, moisture and instability will
develop along that warm front. This along with shortwaves
embedded in zonal flow aloft should result in an increasing
chance for showers and thunderstorms. Initially it will be
mainly to our southwest but with time, our area should become
overtaken by clusters of convection.

The current model suite agrees on wave of low pressure riding
into the region late Saturday night through Sunday as warm
frontal zone also shifts across the area. Jet support aloft - by
getting in the right entrance region of a jet that will be
shifting towards New England - becomes favorable allowing
additional forcing for showers and thunderstorms. Precipitable
water values, especially in Pennsylvania, will reach between
1.75 and 2.00 inches. It will turn quite humid with dewpoints
surging to mid 60s-near 70 Sunday. Thus concern is increasing
for potential locally excessive rainfall, due to slow-moving
frontal zone and possibility of training convection with high
rainfall rates. We will for now hold off advertising this in the
local Hazardous Weather Outlook, until we have a better idea on
how much overlap there may be with the individual waves of
thunderstorms over the weekend. Also, we will need to consider
if that will coincide with areas that have had recent heavy
rains. Additionally, with our region being within the belt of
brisk westerlies aloft, we will need to consider potential for
strong organized storms/possibly severe. Monitor the forecast in
coming days.


345 AM Update...
Transition to drier weather is expected as we head into the
middle of next week, but first there is still potential for
additional showers and thunder Monday.

Precipitable water values appear probable to drop some Monday,
after larger wave of low pressure expected to pass through
during the second half of the weekend. However, main axis of
upper trough aloft will still be swinging through Monday, which
will maintain a decent chance of showers and
thunderstorms/possible secondary wave of low pressure along
departing frontal zone. A few leftover showers could linger
into early Tuesday, otherwise models are in agreement that
Tuesday-Wednesday should be generally dry with slightly below
normal temperatures.


VFR will prevail much of the day. An area of showers and
thunderstorms is expected to track across CNY/NEPA late in the
day and early this evening. Thus, we`ve inserted TEMPO groups
for MVFR showers from about 22-02z.

Later this evening (after 04-05z), fog may begin to form again,
especially at any terminals which receive more significant
rainfall. IFR-fuel alternate restrictions, at the very least,
are expected.


Friday...Other than some early morning fog, VFR.

Saturday through Monday...Chance of showers/storms and
associated restrictions.




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