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640
FXUS61 KBGM 211440
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
1040 AM EDT Tue Aug 21 2018

.SYNOPSIS...
As a storm system, moves across southern Canada, it will drag a
frontal complex through the region, today and tonight. These
fronts will bring showers to the area, and possibly a
thunderstorm. Scattered showers could linger into Wednesday,
with an upper level disturbance in the vicinity. Drier weather,
with pleasant air, is expected later this week.

&&

.NEAR TERM /THROUGH TONIGHT/...

1035 AM UPDATE...Light showers just now pushing into the south
and west parts of the area. Models continue to show the
precipitation weakening as it spreads east today, with little
chance of thunder. Previous weather grids are in excellent
shape for timing and coverage, so only minor adjustments to the
grids at this update. Previous discussion below.

430 am update... Lower clouds are streaming northward into
CNY/NEPA this morning, owing to a moist southeasterly flow. This
maritime type flow pattern will only strengthen today, ahead of
a surface warm front approaching from western NY/PA. Thus, skies
will remain overcast, which will limit heating, and cap
afternoon highs in the low-mid 70s.

An upper low, evident on satellite imagery early this morning
over the upper Midwest, is expected to open up today and head
northeastward, reaching Ontario and Quebec by this
afternoon/early evening. The associated surface low will follow
a similar path, dragging the aforementioned warm front through
the forecast area this evening, followed quickly by the cold
front/occlusion overnight into early Wednesday. An area of
showers across the OH Valley, Lake Erie, and western PA early
this morning, is shown by most of our near-term guidance to
track across CNY during the midday and early afternoon hours.
Reduced heating (mentioned earlier) should all but eliminate any
thunder potential for much of the day.

Things get a little more interesting this evening, as a narrow
warm sector edges briefly into CNY/NEPA. Most high resolution
model members show the potential for a linear convective
feature to cross the forecast area, ahead of the approaching
cold front/occlusion. ML CAPE values could reach 500-750 j/kg
this evening, particularly across our western counties (from the
Finger Lakes region down towards Bradford county PA), along with
fairly decent low-level shear (0-1 km SRH values in the 100-200
range for a time). This environment could be supportive of a
few strong wind producing and/or rotating storms. We`ll continue
to monitor this potential today.

Additionally, a stream of fairly deep moisture will get drawn
northward for a brief time tonight, with precipitable water
values in the 1.75-2" range, leading to the possibility of heavy
downpours. Given our sensitivity from recent heavy rainfall, the
potential for isolated poor drainage area flooding, or even
flash flooding, will also have to be monitored. The good news
here is that this system looks very progressive, which should
act to limit the overall hydro threat.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
5 am update... Model agreement is good that the surface cold
front will be east of our forecast area by around daybreak
Wednesday, shunting the deeper moisture towards the coastal
plain.

However, a digging short-wave in the northern stream will keep
an upper trough axis present over the eastern Great Lakes
region. Resultant instability and lingering moisture will
probably cause a few showers to form on Wednesday, along with
perhaps a rumble of thunder.

A gradual improving trend should commence Wednesday night, as
the atmosphere stabilizes diurnally, and the upper trough
mentioned above slowly moves east. Any scattered early evening
showers should diminish to a few sprinkles, at worst, overnight.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
345 AM Update...

Thursday through Friday night: After lingering clouds and
perhaps a sprinkle early Thursday morning skies should become
mostly sunny by afternoon. High pressure from Canada will build
into the region by Thursday afternoon resulting in a period of
much needed dry and refreshing weather across the region.
Northwest winds could be a bit breezy midday Thursday (8-15
mph), but will gradually decrease as the high builds later in
the day. High temperatures should be in the 70`s with lows in
the 50`s. With favorable conditions for radiational cooling with
the high overhead Friday morning a few spots may actually fall
into the upper 40`s for morning lows. Some patchy valley fog is
possible Friday morning as well.

High pressure slowly starts to move out Saturday, with one last
mainly dry day expected. A frontal boundary will approach from
the west late in the afternoon, which could touch off an
isolated shower/t`storm. Cloud will slowly increase through the
day as well. Morning lows are expected to fall into the upper
50s/low 60s and highs generally reach in the mid to upper 70s
and low 80s.

Saturday night: A weak trough and associated warm front slowly
push through the area from the west. This will bring a chance of
showers and a slight chance of t`storms to much of the forecast
area. It will not be as cool, with lows in the mid-50s to
around 60.

The shortwave trough remains near the region into the day on
Sunday. Instability is forecast to really begin ramping up as a
much warmer, more humid air mass moves into our area. An
expansive upper level ridge builds over the Mississippi/Ohio
valley region which will allow a southwesterly flow to develop.
Continued with chance PoPs for afternoon showers/t`storms under
the unstable air mass...especially across Central NY. High
temperatures rise into the lower and mid-80s, with dewpoints
reaching the upper 60s.

The upper level ridge continues to strengthen over the Ohio
Valley early next week. This will keep Central New York and
Northeast PA in a fast moving westerly flow pattern along the
northern periphery of the ridge. This type of pattern usually
yields chances for fast moving, gusty wind producing
thunderstorms; as oppose to the slow moving, widespread heavy
rain producers we have had recently. Kept the chance PoPs north
across central NY, further away from the center of the
anticyclone...fading to slight chance over NE PA. The late
summer heat continues to build, with highs reaching 85-90 in the
valleys, with lower 80s in the higher elevations. This is a
solid 10 degrees above average.Overnight lows will be in the mid
to upper 60s. With dewpoints pushing 70, daytime heat indexes
could be well into the 90s in the urban valleys.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
12z update... At least periodic lower ceilings are expected
today at KELM, KITH, KBGM, and KAVP, within a moist S-SE flow.
Restrictions should be generally within the MVFR-fuel alternate
range. KSYR and KRME should stay mainly VFR today, outside of
possible brief restrictions in showers this afternoon.

Two distinct periods of showers are anticipated. The first
should come through roughly 16-22z, with the second, perhaps
steadier/heavier batch during the evening, after 00-02z. Some
thunder is also possible this evening, but uncertain coverage
precludes mention in the terminal forecasts at this early
juncture.

Tonight, lower ceilings should evolve area-wide with time, owing
to more persistent showers/deeper moisture, out ahead of an
approaching cold front. Although periodic IFR cannot be ruled
out, we`ve again indicated MVFR-alternate required.

E-SE surface winds should pick up later this morning, averaging
8-12 kt into this evening. Occasional gusts near 20 kt are also
possible this afternoon, especially at KITH. S-SE winds mostly
5-8 kt are expected tonight, with locally stronger gusts
possible near any thunderstorms.

Outlook...

Wednesday morning...Restrictions probable in lingering lower
ceilings/showers.

Wednesday afternoon through Saturday...Mainly VFR. Early
morning fog possible, especially KELM.

&&

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

&&

$$
SYNOPSIS...DGM/MLJ
NEAR TERM...DGM/MLJ
SHORT TERM...MLJ
LONG TERM...HLC/MJM/MWG
AVIATION...MLJ/RRM