Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 252052

Area Forecast Discussion
National Weather Service Buffalo NY
452 PM EDT Wed Apr 25 2018

Low pressure will move northeastward across New England tonight and
into the Canadian Maritimes on Thursday. Lingering showers behind
this system tonight will give way to drier weather from west to east
on Thursday as high pressure and drier air builds across the Lower
Great Lakes. Two more weak systems will then bring additional
periods of rain showers Friday and Saturday.


Tonight two shortwave troughs will gradually merge and consolidate
across New York State...while supporting the continued deepening
of an attendant surface low tracking from the mid Atlantic coastline
into New England. On the backside of this system...the combination
of a westerly to northwesterly cyclonic upslope flow of cooler
air...increasing wraparound moisture...and lift attendant to the
northern (and stronger) trough will support relatively high
probabilities of additional rain showers across the bulk of our perhaps for portions of far southwestern New York.
Winds will also become breezy with a tightening pressure gradient
over the Eastern Great Lakes between the New England low and High
Pressure building into the Ohio Valley. Low temperatures will drop
into the mid 30s to around 40 tonight with cold air advection
beneath lingering cloud cover. Patchy fog will again become possible
overnight with saturated low levels.

On Thursday the surface low will exit northeast across the Saint
Lawrence River Valley as high pressure builds across western NY from
the Ohio Valley. Lingering wrap around moisture and upslope flow
will keep a high probability for rain showers east of Lake Ontario
through the morning which will taper off in the afternoon. Clearing
skies will bring sunshine across western New York by mid/late
morning. A lingering pressure gradient will keep some gusty winds 20-
30mph through much of the day. Neutral temperature advection will
support high temps only peaking in the low to mid 50s except upper
40s close to the eastern lake shores. Total additional rainfall from
this afternoon through Thursday will range from one to two tenths of
an inch across the Southern Tier to three quarters of an inch across
the North Country.


A weak ridge of high pressure will build into the eastern Great
Lakes on Thursday night with dry weather and clearing skies. Lows
will be in the mid to upper 30s in most locations.

Weak low pressure will track roughly from eastern Virginia to
Southern New England on Friday. There remains some model
disagreement on the exact track, with the GFS a bit further north
and wetter than most other model guidance. There is at least a
chance that showers will clip southern and eastern portions of the
cwa on Friday. Expect highs to be in the upper 50s to lower 60s.

By Friday evening a northern stream trough will approach Western NY
which will result in a chance of showers for the rest of the area.
Increasing cold advection will drop temperatures back into the mid
to upper 30s for lows by late Friday night, with lower 40s east of
Lake Ontario.

This trough will usher in colder air and below normal temperatures
for the weekend. Model consensus has 850mb temperatures falling to -
8C as the core of the coldest air moves across the area Saturday
night. This is cold enough for some limited lake enhancement and
also to support snow showers where precipitation still lingers
Saturday night into Sunday. Showers will be light with little if any
accumulation, but this will be perhaps one last taste of winter
before the warm up next week. The forecast hedges below most MOS
based guidance due to high forecast confidence in the cold airmass
and the likely lake enhanced cloud cover during much of the
weekend. Highs will only be in the 40s over the weekend, with
overnight lows near or below freezing on Saturday night.


The anomalously cold upper-level trough will exit the region into the
Canadian Maritimes Sunday night and Monday. Meanwhile, building
500mb heights and an expansive surface high over the Tennessee
Valley will become centered along the Carolinas which will initiate
a strong warning trend across our region. The surface high along the
Carolinas will pump up a much warmer air mass into the Ohio Valley
and Great Lakes which will send high temperatures soaring some +15-
20F degrees above climo by Wednesday with mid-upper 70s, even a
few 80F readings. Late in the week, latest guidance shows a
potent shortwave dropping southeast out of Canada across the
Great lakes while several waves ride northeast along a frontal
boundary to our west. This will likely bring increasing chances
for showers Thursday and Friday. Otherwise, look for relatively
quite weather the first half of the week with dry conditions and
more like summer.


Low cigs and occasional showers will continue across the terminals
into tonight as a trough of low pressure across western and central
New York becomes absorbed into a deepening surface low shifting
north along the East Coast. CIGS will remain at MVFR/IFR with VIS
lowering to IFR in light to moderate showers.

Westerly flow will develop tonight as the surface low shifts from
the Mid-Atlantic into New England. This will allow additional
showers, low clouds and fog to continue in wrap around moisture.
Expect IFR VIS/CIGS overnight with CIGs lifting to VFR Thursday
morning with low level drying across western New York. KART will see
continued chances for showers and low cigs lingering into the


Thursday night...VFR.
Friday and Saturday...Mainly VFR with a chance of showers.
Sunday...Mainly VFR with a chance of rain or snow showers east
of Lake Ontario.


Surface low pressure along the mid Atlantic coastline will continue
to deepen tonight as it lifts into New England with westerly winds
freshening tonight into Thursday. Westerly winds will produce
sufficient waves and winds on the southern and eastern shores of
Lake Ontario for Small Craft conditions into Thursday night. Light
winds and waves expected through Friday with perhaps waves building
in westerly flow again on Saturday.


MARINE...Small Craft Advisory from 9 PM this evening to 8 PM EDT
         Thursday for LOZ043.
         Small Craft Advisory from 9 PM this evening to 5 PM EDT
         Thursday for LOZ042.
         Small Craft Advisory from 11 PM this evening to 11 PM EDT
         Thursday for LOZ044-045.



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