Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 182331

Area Forecast Discussion
National Weather Service Buffalo NY
731 PM EDT Mon Sep 18 2017

A weak cold front will stall just to the west of Western New York
tonight and Tuesday. This front may produce a few scattered showers
across Western New York this evening and again Tuesday afternoon.
Otherwise dry and warm weather will continue through next weekend as
high pressure remains in place across the eastern Great Lakes.


Surface analysis shows a stalling cold front to our west across
southern Ontario this evening, with a weak convergence zone noted
across Western NY near the Cattaraugus/Allegany County border
extending north to between Buffalo and Rochester. This subtle
convergence zone has provided just enough focus for scattered
showers and a few isolated thunderstorms during the early evening.
These showers will taper off this evening with the loss of daytime
instability and break down of the convergence zone. Otherwise the
cloud cover over Western NY will slowly erode from east to west
overnight as subsidence near the western periphery of the upper
level outflow from Jose approaches the area. This will provide
partial clearing overnight.

Temperatures will continue to be mild, with lows in the low to mid
60s on the lake plains and upper 50s in the cooler Southern Tier
valleys and Lewis County. Expect typical river valley fog again late
tonight across the western Southern Tier.

On Tuesday the area will remain in a squeeze play between ridging
and upper level outflow to the northwest of Jose and a washing out
cold front just to our west across southern Ontario. Model guidance
has trended west with the stalled frontal zone over the past 24
hours, and most of the focus for any scattered showers and
thunderstorms Tuesday afternoon will be along the remnant frontal
zone across Southern Ontario. Some high resolution mesoscale
guidance suggests a few isolated showers may develop Tuesday
afternoon across far Western NY along lake breeze boundaries, but
even here the vast majority of the time will be rain free. From the
Genesee Valley eastward, subsidence and dry air will prevent any
diurnal showers and provide more in the way of sunshine.

Temperatures will continue to run a solid 10 degrees above normal,
with highs in the lower 80s across lower elevations and mid to upper
70s for higher terrain and near the immediate lakeshores as local
lake breeze circulations develop.


While Hurricane Jose could provide some very unsettled weather along
parts of the Northeast coast during this period...there is NO doubt
that our region will continue to enjoy fair dry weather with
temperatures that will average well above normal.

Remember that persistent trough that lingered over the Lower Great
Lakes through the summer? Well...the large scale pattern has finally
broken down so that the dominant ridging will now be found in the
East. The details...

Phasing of an increasingly amplified flow will take place over the
country during this period...and this will lead to height and
temperature fields that will be as much 3 STD above/below normal
(pending side of the country). For our interest over the Lower Great
Lakes region...H5 heights will rise to an average of 590dm while H85
temps will moderate through the mid teens c. This will most
certainly keep a summery airmass in place with strengthening
subsidence and ample sunshine helping to maintain afternoon
temperatures in the 80s. The warmest of these three days (Wed-Fri)
should be Friday when the mercury could top out in the mid 80s
across the bulk of the lake plains.

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


It can be stated with high confidence that we can look forward to
more 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 80s.
The warmer valleys will likely 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.


A few scattered showers across the higher terrain well southeast of
KBUF will dissipate by mid to late evening. Otherwise areas of mid
level clouds across Western NY will slowly scatter out from east to
west late tonight and Tuesday morning. Expect typical valley fog and
local IFR across the western Southern Tier overnight and Tuesday
morning, roughly from 06Z-14Z. Some low stratus may also develop
across the higher terrain near the PA state line with additional IFR

Following the morning fog and low stratus across the western
Southern Tier, VFR will prevail for the rest of Tuesday. A few
isolated showers may develop across far Western NY during the
afternoon with very sparse coverage. Otherwise expect mid level
clouds and diurnal cumulus across Western NY, and just high clouds
east of the Genesee Valley.

Wednesday through Saturday...Mainly VFR. Local IFR conditions each
late night and early morning with Southern Tier valley fog.


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 next
weekend with ideal boating conditions, but not much wind for sailing.





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