Area Forecast Discussion
Issued by NWS Buffalo, NY

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210
FXUS61 KBUF 201822
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
222 PM EDT Wed Sep 20 2017

.SYNOPSIS...
Warm temperatures and dry conditions will persist through the
remainder of the week and the coming weekend, as high pressure will
remain in place across the region.

&&

.NEAR TERM /THROUGH THURSDAY/...
Surface analysis late this morning showing western and central New
York are sandwiched between Jose southeast of Long Island and an
occluded frontal system pushing across the upper Midwest. Surface
high pressure centered over western Quebec is ridged south across
the eastern Great Lakes with 500mb analysis placing a 583dm ridge
overhead. All morning fog has dissipated with some lingering
low stratus over and along the south shore of Lake Ontario.

Dry, warm and humid conditions will continue this afternoon with
mainly sunny skies and light northeast winds. Some diurnal cumulus
may develop in spots where lingering moisture from morning fog is
available including the western Southern Tier. 850 mb temperatures
warming to around +16C with the mostly sunny skies will lead to
temperatures similarly as warm as yesterday. Highs are expected to
range from the upper 70s in higher terrain to low/mid 80s at lower
elevations. Dewpoints in the 60s will keep a humid feel to the
airmass.

Tonight, high pressure will remain over the region with light winds
and clear skies again allowing for radiational cooling fog formation
overnight. Fog is most likely in the Southern Tier valleys as well
as the Black River and Saint Lawrence River valleys.

Thursday will be another near carbon-copy of today with perhaps the
only differences being the mid-level ridge strengthening to 588dm
and 850mb temps warming a degree to +17C. The high pressure surface
and aloft will keep dry and warm weather in place with high temps
again warming into the low to mid 80s or 10-15 degrees above normal
September levels. Dewpoints holding in the 60s will keep a humid
feel to the airmass.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
Two words will summarize this time period...DRY and WARM.

There will be an amplifying upper level pattern in place during this
time period with equally anomalous height departures found over each
half of the country. For our interest here in the Lower Great Lakes
region...H5 heights will average close to 590dm...which is 2-3 STD
higher than where they should be for this time of year. The staunch
summer-like ridge...which will be centered over the Mid-West and
Lower Great Lakes...will support unusually warm conditions as well.

H85 temperatures that will start off in the mid teens C will further
warm to the upper teens C by the weekend. This will encourage
additional day to day warming so that by Saturday...max temps will
be in the mid to upper 80s F. Given the increasingly dry antecedent
conditions...its not out of the question that select locations in
the Genesee Valley (ie. Dansville) and in the typically warmer
valleys of the Southern Tier would reach 90. If this were mid
summer...when the sun angle would be more than 20 deg greater...then
we would likely be talking about increasingly uncomfortable
conditions and possibly some oppressive heat (esp this weekend).
Luckily for us...the Gulf of Mexico will be cut off..so dew points
for much of the period will generally range from the upper 50s to
lower 60s.

Meanwhile the nights will feature mainly clear skies with the
resulting favorable radiational cooling producing fog in open...
outlying areas...and particularly in the Southern Tier valleys. Mins
will range from the mid and upper 50s across the Southern Tier and
parts of the North Country to the low to mid 60s across the lake
plains.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
It can be stated with high confidence that we can look forward to
continued fair weather during this period...along with continued mid
summer warmth (temperatures that will be more typical of late July-
early August).

An anomalously amplified pattern will be locked in across the
country during this time frame...with 590dm heights over the Lower
Great Lakes averaging some 2-3 STD above typical late Sept values.
The associated subsidence and lack of significant moisture will keep
sunny skies over our region by day...with H85 temps in the upper
teens c supporting widespread afternoon max temps in the mid to 80s.
The warmer valleys will experience highs in the upper 80s. These
temperatures will average some 15 to 20 degrees above normal.
Meanwhile at night...mins will continue to range from the mid and
upper 50s across the Southern Tier and parts of the North Country to
the low to mid 60s across the lake plains.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Stratus coming off of Lake Ontario has finally mixed out this
afternoon, leaving widespread VFR skies in place across the forecast
area. Expect VFR conditions to prevail through the evening hours,
however with high pressure, light winds, and clear skies in place
tonight, expect fog to redevelop again tonight after 03-06Z. Similar
to last night, IFR/LIFR conditions are expected at KJHW/KROC and
potentially KIAG. KART may escape the fog tonight, as synoptic NE
flow may be strong enough to keep the lowest levels mixed - however
should the wind drop off later this evening, then fog formation is
likely. IFR/LIFR conditions will rapidly improve after 12-13Z on
Thursday, with another VFR day on tap for the area, as high pressure
will remain in place.

Outlook...

Thursday night through Tuesday...VFR. Local IFR conditions each late
night and early morning with fog.

&&

.MARINE...
High pressure will remain in place across the Lower Great Lakes
right through next weekend. This will provide a long stretch of very
light winds and flat wave action for the rest of the week and
weekend with ideal boating conditions, but not much wind for sailing.

&&

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

&&

$$

SYNOPSIS...CHURCH/SMITH
NEAR TERM...SMITH
SHORT TERM...RSH
LONG TERM...RSH
AVIATION...WOOD
MARINE...HITCHCOCK/THOMAS



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