Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 230842
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
442 AM EDT Tue May 23 2017

.SYNOPSIS...
A weak ridge of high pressure will bring dry weather today through
most of Wednesday with temperatures above normal. Low pressure will
then bring more rain to the region Wednesday night and Thursday with
temperatures closer to normal.

&&

.NEAR TERM /THROUGH TONIGHT/...
Surface high pressure spans from the upper Ohio Valley northeast
across PA and NY this morning. Subsidence brought on by convergent
flow aloft will continue to support mainly clear skies across
western and central NY. Low temperatures will run in the upper 40s
to around 50 on the lake plains, with low to mid 40s in the cooler
sections of the interior Southern Tier and Lewis County.

The surface high will slowly shift northeast through today and
tonight. Further north a weak mid level shortwave will move
northeast across southern Ontario with little direct impact on our
area although it will bring scattered showers and thunderstorms
north of the Canadian border. While we will remain dry today, the
shortwave will bring some increase in moisture and cloud cover, with
both mid level clouds and diurnal cumulus expected across the
region. Stable lake shadows will allow more sunshine northeast of
Lakes Erie and Ontario. Temperatures will rebound to around 5
degrees above normal with the southerly flow. Highs expected to run
in the lower to mid 70s away from lake influences. Weak synoptic
scale flow and strong differential heating will allow local lake
breezes to develop with winds becoming onshore along all the
shorelines in the afternoon, keeping temperatures cooler within a
few miles of the lakes.

Tonight, the surface high will weaken over New England while a mid-
level ridge axis shifts over the eastern Great Lakes region. This
will continue fair weather while warm advection aloft and a bit more
cloud coverages holds overnight temps above normal. Lows should only
slip back into the low to mid 50s with some mid-upper 40s possible
in the colder valleys of the western Southern Tier.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Bubble of high pressure becoming centered across New England will
maintain dry weather across the area through the first half of
Wednesday.

High pressure will exit the region Wednesday as a deepening surface
low slowly tracks into the Ohio Valley. Model tracks differ
slightly, but most of the guidance eventually tracks this low across
Ohio Wednesday night and across Lake Erie on Thursday. Increasing
moisture transport and lift on the front side of the approaching low
will eventually allow precipiation to blossom across the area. Onset
time may be slowed a bit from continuity based on slower track of
approaching surface low. Warm air advection and slower timing of
precipitation onset should allow high temperatures Wednesday to
reach the lower to mid 70s.

Does look like there will be at least a solid 6 to 12 hour period of
fairly steady rain starting late Wednesday in the far west and
filling in across the rest of the area through Thursday. The steady
rain should taper to more showery weather by Thursday night as the
surface low starts to shift east of the area.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Our region will be under the influence of a progressive...northern
branch of a split flow during this period. While this will allow for
fairly frequent shower activity...a closed off GOMEX will keep
rainfall amounts to a minimum. This pattern will also keep
temperatures from straying too far from normal...but on average...
they will tend to run a few degrees above typical late May values.
Breaking this down on a day to day basis...

A stacked storm system over eastern New York Friday morning will
exit across New England during the afternoon and evening. This will
keep some showers in place over our region...particularly east of
Lake Ontario where pops will be raised to likely. Temperatures on
Friday will climb into the 60s.

Ridging will build across the Lower Great Lakes late Friday night
and Saturday. While the models are not convinced that dry weather
will prevail during this time frame...am fairly confident that the
aforementioned ridging and lack of mid level moisture will translate
into fair dry conditions. This should also help Saturday afternoon
temperatures climb into the 70s across most of the western counties.

As the ridge pushes east of our region Sunday and Monday...the next
longwave trough will dig across the Upper portions of the
Mississippi Valley and Great lakes region. This will result in
deteriorating conditions...particularly late Sunday into Monday. In
other words...as it stands now we should be able to get through most
of Sunday before the skies `open` again. Given the inconsistencies
between the medium range ensembles though...confidence is lower than
normal.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
A weak ridge of high pressure slowly shift over the eastern Great
Lakes region through tonight with VFR cigs/vis expected. Weak warm
advection and diurnal cumulus will bring some increase in cloud
cover as a disturbance moves north of Lake Ontario but CIGS will
remain VFR with light southwest winds. The high pressure will
continue to bring VFR and fair weather through tonight.

Outlook...

Wednesday...VFR.
Wednesday night...VFR/MVFR with a chance of showers.
Thursday...VFR/MVFR with showers likely.
Friday...VFR/MVFR with a chance of showers.
Saturday...Mainly VFR.

&&

.MARINE...
Weak high pressure shifting over the Lower Great Lakes today through
Wednesday will provide light winds and little wave action through
the middle of the week. A storm system will pass over our region
Wednesday night through Friday but winds and waves will remain below
advisory levels.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...SMITH
NEAR TERM...SMITH
SHORT TERM...TMA
LONG TERM...RSH
AVIATION...SMITH
MARINE...SMITH



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