Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 221843

Area Forecast Discussion
National Weather Service Buffalo NY
243 PM EDT Sat Apr 22 2017

Low clouds will gradually scatter out this afternoon, though high
clouds will keep sunshine filtered. Skies will gradually clear
overnight, as a ridge of high pressure builds into the region, with
sunny skies and warmer temperatures expected Sunday. The next chance
for precipitation will be Monday night into Tuesday, as a low
pressure system drifting up the Eastern Seaboard sends
Atlantic moisture back across New York state.


A peek at satellite imagery this afternoon reveals widespread
clearing just upstream of our area across the central Great Lakes
and Upper Midwest, courtesy of an elongated upper level ridge that
extends from the Rockies and extends across the northern Plains and
into the Great Lakes. This clearing has yet to reach our forecast
area, however. Moisture wrapping across the area associated with a
departing trough has meant that cloud cover has been slow to erode,
a factor compounded further by the fact that high clouds are
streaming across the area from a slow-moving low pressure system
over the Tennessee valley. Even as the low clouds continue to slowly
clear out, the high clouds will provide, at best, filtered sunshine
this afternoon into this evening. As such, have knocked back
forecast high temperatures this afternoon by a couple of degrees.

Skies should clear out overnight however, as the aforementioned
trough and low level moisture completely clear the area, and the
upper level jet that is advecting the high clouds overhead shifts
slightly to the east overnight. With Western New York already on the
edge of this high cloud shield, it is reasonable to assume that
clearing from west to east should follow overnight. With this
clearing and light winds as high pressure moves overhead,
temperatures will fall sharply overnight, with widespread lows in
the 30s, and some locales in the Southern Tier and North Country
dropping to the freezing mark. Given the light winds/radiational
cooling reminiscent of autumn, along with recent high waters, have
elected to throw in some patchy fog into the river valleys of the
Southern Tier late tonight/early Sunday morning.

After a chilly start to the day, things will warm up nicely on
Sunday, which should prove a marked contrast to the dreary
conditions of the last couple of days, as high pressure noses across
the region. Abundant sunshine will allow temperatures to warm into
the low to mid 60s, with some locations in the valleys of the
Southern Tier and the Genesee valley creeping into the upper 60s.
The one exception will be immediately downwind of the lakes, where
the clear skies should promote the formation of the lake breeze in
the afternoon, helping to depress temperatures along the shorelines
east/northeast of both lakes, with highs only topping out in the
upper 40s to mid 50s.


High pressure and fair weather will dominate our region during the
first half of this period. While a dying weak cold frontal boundary
could bring some clouds to the Saint Lawrence Valley and adjoining
portions of the North Country Sunday night...dry weather and mostly
sunny/mainly clear skies should otherwise prevail. Temperature-wise...
850 mb temps of +3C to +7C should generally promote highs ranging
through the 60s both days...though developing lake breezes will
result in cooler readings along the immediate lakeshores Sunday...
with a general northeasterly low level flow then similarly bringing
cooler temps to areas along and a bit inland from the south shores
of the lakes on Monday. In between...Sunday night will feature lows
in the mid 30s to lower 40s.

Monday night and Tuesday a cutoff low and its associated surface
reflection will meander its way northeastward along the southeastern
U.S. coastline. An influx of Atlantic moisture around the northern
flank of this system will bring an increase in cloud cover to our
region...along with the potential for some showers later Monday
night and Tuesday. With the 00z/22 guidance suite slowly coming
into better agreement that this system could bring a little light
precip into our region...have bumped PoPs up a little further from
continuity...though these still remain in the chance category and
range from 20s/30s across far western New York to 50s across the
North Country...with the greatest shower potential coming during
the day Tuesday. As this system lifts further northeast and off the
Atlantic coastline Tuesday night...its associated moisture field
should recede off to our east...resulting in a return to mainly
dry and quiet weather for our region. As for temperatures...these
will remain pleasantly above average...with lows mostly in the lower
40s Monday night again followed by highs ranging through the 60s on
Tuesday...with lows then dipping into the mid 40s to lower 50s to
close out the period Tuesday night.


On Wednesday...a sharpening upper level ridge will be found across
our between the weakening cutoff low passing by well to
our east...and the next mid and upper level trough developing into
the Great Lakes and Upper Midwest. The combination of strong subsidence
under this ridge and warm advection attendant to a developing southerly
downslope low level flow will help drive 850 mb temps up to between
+10C and +12C across our region...which should translate into a pretty
nice day with highs warming into the 70s areawide...and widespread
highs in the mid to upper 70s found south of Lake Ontario.

Wednesday night and Thursday the medium range guidance remains in
good agreement on the next modest surface low lifting from the Great
Lakes into north-central Quebec while dragging its associated weak
cold front across our region...though it has also trended a bit slower
with the timing of the frontal passage. As a result...the bulk of
any shower/possible thunderstorm activity with the front should hold
off until Wednesday night and Thursday...when broadbrush chance PoPs
will be in place. Otherwise...temperatures should remain solidly above
average especially when given the slower timing of the front...with
lows in the lower to mid 50s Wednesday night followed by highs in the
mid 60s to lower 70s on Thursday.

Thursday night and Friday a second and potentially stronger surface
low looks to lift northeastward across the Midwestern states and Great
Lakes...albeit a little more slowly than seen in previous guidance
packages. This should eventually result in a surface warm front and
some showers/possible thunderstorms working into our region on Friday...
while temperatures continue to average significantly above normal.

Looking out beyond the end of this period...the 00z/22 guidance suite
still suggests the potential for a period of midsummerlike warmth
sometime next weekend or early in the following week...when daytime
highs could reach well into the 80s.


MVFR cigs continue to scatter out this afternoon, as low level
moisture is continuing to gradually depart the area with a departing
trough. High clouds will linger into the evening hours however,
before skies clear overnight as the upper level jet advecting the
clouds across our area moves to the east. This will result in
widespread clearing overnight, with widespread VFR across most
locations. The only exception will be in the Southern Tier, where
radiational cooling may promote the formation of fog in the river
valleys. Otherwise, clear skies and light winds will prevail on
Sunday, with only a light southwesterly lake breeze developing in
the afternoon.


Sunday Night and Monday...VFR.
Tuesday and Wednesday...Mainly VFR with a chance of showers.
Thursday...VFR/MVFR with a chance of showers and thunderstorms.


High pressure  moving into the region will result in tranquil
conditions on the lakes through Sunday night. Northeasterly winds
will freshen on Monday, as a slow moving area of low pressure moving
up the Eastern Seaboard  draws closer to the lakes, reorienting the
pressure gradient across the area. This will produce choppy
conditions along the southern shores of the lakes Monday afternoon
into Monday evening, though conditions should relax somewhat by
Tuesday, as winds shift to the southeast.



Overall, faster responding creeks across the forecast area will
continue to recede from higher levels due to recent heavy
rainfalls over the next 24 hours. Slower responding creeks, such
as Tonawanda Creek and Black Creek in Churchville, will
continue a gradual rise over the next 24 hours however. In
addition, a log jam on Tonawanda Creek in the Town of Royalton
is causing the creek to back up, producing localized flooding
and road closures. An areal flood warning remains in effect for
this localized hazard. Otherwise, dry weather expected through
the weekend will allow water levels to continue an overall
downward trend for at least the next few days.





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