Area Forecast Discussion
Issued by NWS Buffalo, NY

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268
FXUS61 KBUF 211433
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1033 AM EDT Fri Apr 21 2017

.SYNOPSIS...
A cold front will finish crossing our region this morning with
showers east of Lake Ontario ending by early afternoon. In its wake,
mainly dry and uneventful weather will follow for the weekend and
early next week. Temperatures will remain cool through Saturday
before a notable warming trend next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Radar imagery showing a narrow band of showers moving slowly across
the Tug Hill region, with rain coming to an end in Lewis County by
early afternoon as the cold front moves east of the area. Farther
west, overcast skies are still in place across Western NY late this
morning with some fog near the Lake Erie shore including downtown
Buffalo. A narrow slot of dry air and sunshine is found across the
western Finger Lakes.

Going through the afternoon, expect clouds to persist across Western
NY, with the break of sunshine in the western Finger Lakes likely
filling in with more cloud cover. This will yield a good amount of
cloud cover in most areas through the afternoon with just a few
brief interludes of sunshine.

As for temperatures...850 mb readings will average from +1C to +3C
by early this afternoon... which in conjunction with good mixing
should be supportive of highs in the upper 50s to lower 60s in most
places. The exceptions to this will be downwind of the lakes...where
an onshore flow will keep highs confined to the the lower 50s
including much of Western NY under thicker clouds cover.

Tonight the surface low will slowly make its way across Southern
Quebec. The cyclonic flow around the low will help advect a secondary
trailing area of low level moisture into our region from the west
and northwest...and this in combination with increasing upsloping
should result in the redevelopment of fairly widespread lower
clouds across the region...with a few spotty light sprinkles also
becoming possible out of these very late tonight. Otherwise the
night will be dry and uneventful...with overnight lows ranging
from the upper 30s to lower 40s.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
A progressive pattern will be in place across the country during
this period...as a low amplitude...problem-free northern branch of a
split flow will dominate the Great Lakes region. The fair...
uneventful weather will be accompanied by temperatures that will
average a little below normal...particularly daytime highs. As for
the day to day details...

A mid level trough (in the process of shearing out) will cross our
forecast area during the day Saturday...while expansive surface high
pressure centered over the Upper Mississippi Valley will nose to the
east across all of the Great Lakes region. The latter will supply us
with enough subsidence to support fair dry weather...although there
will still be a fair amount of cloud cover in place...particularly
through early afternoon. It will also be quite cool. H85 temps in
the vcnty of zero c will only allow the mercury to climb to within a
few degrees of 50 f...with most areas remaining in the 40s.

In the wake of the exiting mid level trough...continued drying of
the low levels Saturday night will lead to clearing skies and a
chilly night. Sites away from the lakes will drop into the 30s...
with readings as low as freezing in some of the colder Southern Tier
valleys or up on the Tug.

A large arctic high centered over the northern reaches of Manitoba
on Sunday will extend southeastward across Ontario to the Lower
Great Lakes Sunday afternoon into Monday. This will keep fair dry
weather in place across our region with temperatures making a brief
attempt at returning to near normal levels for Sunday.

In a change from continuity...both the operational GFS and ECMWF are
now suggesting that Atlantic moisture will stream back across our
region late Monday night within a deepening easterly flow. This
moisture will be circulated back across our region ahead of a
coastal storm that will be centered off the coast of the Carolinas.
Have thus increased cloud cover and raised pops to slgt chc for
parts of the Finger Lakes and Southern Tier.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
Our region will largely remain under the influence of a progressive
low amplitude pattern found within the northern branch of a split
flow over the country. While this pattern is not conducive for
significant weather...a deep easterly flow found ahead of a southern
stream storm system will direct enough Atlantic moisture back across
our region to support some shower activity during the day Tuesday.
This will mainly be the case for sites east of the Genesee Valley.

A weak frontal boundary...or more likely just an inverted sfc
trough...is forecast to be nearly stationary just to our west on
Wednesday. A southerly flow ahead of this feature will pump very
mild into our region...with H85 temps forecast to be in the vcnty of
9 to 12c. This will easily support max temperatures in the 70s for
the vast majority of the region...with nothing more than an
afternoon shower or two.

The mild weather will continue on Thursday...as a vigorous storm
system ejecting out of the southern Rockies will promote an
amplifying ridge over the Ohio Valley and Lower Great Lakes. While
this ridging will keep H85 temps in the vcnty of 10-12c...the
aforementioned inverted sfc trough will ease across our forecast
area. This will keep at least the chance for some showers over the
region. Max temps Thursday should once again be in the 70s for most
areas.

A look further down the road includes the likelihood that areas away
from Lakes Erie and Ontario will climb into the 80s for Friday and
Saturday as H85 temps will be in the upper teens c. If this
verifies...and there is high confidence that it will...these
temperatures would be 20 to 25 deg f above normal. There is even a
suggestion by one model that H85 temps could touch 20 deg c on
Saturday. While confidence with this is not high...that would
support 90 deg temps for the Genesee Valley and in some of the Srn
Tier Valleys for Saturday! This last weekend of April will certainly
be a very warm...and possibly hot. Stay tuned.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
Elongated surface low pressure draped from near Georgian Bay to the
northeastern end of Lake Ontario will drift into Southern Quebec today...
while pushing its trailing cold front across the eastern Finger
Lakes and North Country this morning. With the frontal passage...
leftover showers east of Lake Ontario will come to an end by early
afternoon...with dry weather otherwise prevailing. In terms of
flight conditions...a mix of IFR to MVFR conditions in lower stratus
and patchy fog through midday will improve to a mix of MVFR/low VFR
this afternoon as slightly drier air works into our region...and
diurnal mixing helps also helps to induce some drying of the lower
levels.

Tonight expect ceilings to deteriorate again as the departing surface
low circulates a trailing area of low level moisture back into our
region...and as the low level flow veers to more of a northwesterly
direction...resulting in increased upsloping. Expect ceilings to fall
back to the lower half of the MVFR range across the lower elevations...
and to IFR across the higher terrain.

Outlook...
Saturday through Tuesday...Mainly VFR.

&&

.MARINE...
Elongated surface low pressure draped from near Georgian Bay to the
northeastern end of Lake Ontario will drift into Southern Quebec today.
In its wake...a moderately brisk westerly flow of cooler air will
spread across the Lower Great Lakes. On Lake Erie this will result
in winds and waves reaching lower-end advisory levels for a time...
for which a Small Craft Advisory has been hoisted. Elsewhere...
conditions should remain a bit below advisory levels.

After winds turn more northwesterly tonight...high pressure will then
build across the region over the weekend...bringing about a return to
relatively light winds and minimal waves.

&&

.HYDROLOGY...
After rainfall amounts of 1-2 inches Thursday and Thursday evening...
many of the Buffalo area creeks responded with rises to action stage
(and in the case of Cayuga creek...minor flood stage)...however these
are mostly now falling. The one exception to this is Ellicott creek...
which is still expected to crest at minor flood stage late this
afternoon and evening...and for which a Flood Warning remains in
effect.

Elsewhere...there will be rises on the slower responding Rochester
area creeks today...however these should ultimately crest at action
stage.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LEZ040-
         041.

&&

$$

SYNOPSIS...HITCHCOCK/JJR
NEAR TERM...HITCHCOCK/JJR
SHORT TERM...RSH
LONG TERM...RSH
AVIATION...HITCHCOCK/JJR
MARINE...JJR
HYDROLOGY...JJR



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