NWS Forecast Discussion

000
FXUS61 KBGM 231451
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
1051 AM EDT Sat Jun 23 2018

.SYNOPSIS...
A slow moving storm will move into southeast Ontario this
weekend. Showers and a few thunderstorms are forecast for
today and Sunday, before a cold front brings drier air into the
region Sunday night and Monday.

&&

.NEAR TERM /THROUGH SUNDAY/...
1030 am update...
Update to drop chance of showers and thunderstorms now into this
evening. A large area of showers over the Susquehanna Region and
Mohawk Valley is moving northeast and should be out of the area
by 1 pm. Upstream only isolated showers. Models show some
showers and a few thunderstorms moving into the far west mid to
late afternoon. This area stays mainly over the Finger Lakes.
Forcing and instability are both weak. Skies will stay cloudy
to mostly cloudy. Cool temperatures now will rise this afternoon
as the low level flow shifts from SE to S. Highs mid to upper
60s far east for Oneida to Sullivan Counties and low 70s
elsewhere.

previous discussion...
A low pressure storm system sliding toward Southern Ontario will
extend a frontal boundary across PA, while a southerly flow
imports increasingly humid air into our forecast area. A series
of waves will rotate out of an upper level storm and move
across NY and PA through today, bringing batches of showers and
thunderstorms to our region.

MLCAPE values are progged to increase over Western NY and PA to
between 600-1000 j/kg early this afternoon, then advect into
our region (mainly west of I-81). This will increase the
potential for afternoon thunderstorms, some of which are likely
to produce heavy downpours due to PWAT values close to 1.50
inches.

A relative lull in the convection is forecast overnight as
instability decreases and the wave energy moves away from us.

An additional round of showers and thunderstorms is expected on
Sunday as the cold front sweeps toward Lake Ontario. Again,
MLCAPE values are sufficient for supporting convection, and
PWATs hold around 1.50 inches. Bulk shear is in the 25-35 knot
range, not especially impressive or indicative of organized
convection.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
400 AM Update...
Fairly quiet period foreseen in the short term, with unusually
dry Canadian high pressure taking charge.

Moisture quickly becomes shallow as front exits Sunday night.
Lingering showers-isolated thunder will diminish though moisture
under developing subsidence inversion will at least temporarily
keep a layer of clouds going through most of the night, with
lows of 50s-near 60.

For Monday and Tuesday, soundings have more of a May look to
them instead of late June, in that there will be a tremendous
amount of dry air above the boundary layer. The models typically
struggle to mix down enough dry air/low enough dewpoints and
thus also enough of a Temp-Dewpoint spread. For both afternoons
we undercut dewpoints while adding slightly to the highs. Also,
as the high pressure drifts directly overhead Monday night the
dry air should radiate extremely well; thus we have also
undercut expected lows. Indeed quite chilly and crisp as
temperatures settle into mid 40s-near 50 by dawn. Some of our
typically coldest spots could even sneak into lower 40s.

An upper wave will zip by on Monday yet with very little
moisture to work with, and thus we were able to go with a
totally dry forecast at this point. And of course remaining dry
with the high pressure Monday night through Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
415 AM Update...
Main feature of interest will be a trough-shortwave tandem that
will probably touch off a round of convection late Wednesday-
Wednesday night. Beyond then, things turn rather warm and muggy.

Models are actually in quite good agreement on a well-marked
shortwave arriving late Wednesday afternoon or Wednesday
evening. Atmosphere by this time will be fairly unstable, and
deep at least moderate shear is present. It appears likely that
showers and thunder will roll through the region during that
time period. Uncertainty exists for how strong the convection
could be; it will be dependent on heating considering the
increased cloud cover ahead of it. Where models disagree, is on
whether the warm air advection side of the system can manage to
produce showers/embedded elevated thunder late Tuesday night-
early Wednesday. ECMWF is driest in this regard, and considering
how devoid of moisture the column will be prior to this event as
well as thermal capping, we have held back chances to only
slight range for now until the much better likelihood with
trough itself late Wednesday-Wednesday night.

Beyond Wednesday night things get more muddled. Heat and
humidity will try to build over the region yet we may remain
within striking distance of waves translating through the
westerlies. Much of the time we may be too capped for
convection, but there is uncertainty on that. For now kept
chances of showers/thunder only in the 20-40 percent range.
Dewpoints are expected to be in the mid to upper 60s which
along with highs of 85-90 in the lower elevations Thursday-
especially Friday will feel more like the middle of Summer.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
Rain showers are increasing across the region this morning, with
ceiling heights falling to between 1500 and 2500 feet at our
terminals.

A brief break in the clouds is possible Saturday afternoon as
rain slides northeastward. A round of showers and thunderstorms
is forecast for Saturday evening, with MVFR conditions
prevailing into Sunday morning. Some of the thunderstorms will
include heavy downpours.

Outlook...

Sunday through Sunday night...Showers and restrictive
conditions are possible.

Monday and Tuesday...VFR.

Wednesday...Restrictions possible in showers and storms.

&&

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

&&

$$
SYNOPSIS...DJP/TAC
NEAR TERM...DJP/TAC
SHORT TERM...MDP
LONG TERM...MDP
AVIATION...DJP

NWS BGM Office Area Weather Forecast Discussion