Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 252155

Area Forecast Discussion
National Weather Service Buffalo NY
555 PM EDT WED MAY 25 2016

Summertime weather is on its way with highs climbing through the 70s
and into the 80s by this weekend.  Along with the warmer
temperatures, an increase in humidity will also bring back
increasing chances of showers and thunderstorms each day leading up
to and into the Memorial Day weekend.


A peek at satellite imagery this afternoon reveals clearing skies
across a good portion of Western and North-Central New York as
mid/upper level ridging is moving into Western NY. The only
exception is a broken band of clouds stretching from the St.
Lawrence Valley south along the Lake Ontario shoreline, like the
products of convergence between southwesterly synoptic flow and the
lake breeze near the Lake Ontario shoreline and, in the case of the
St. Lawrence Valley, convergence just ahead of a weakening cool
front. Nonetheless, this convergence appears to be just strong
enough to generate a couple of showers that are currently wandering
across the St. Lawrence River into Jefferson County.

With the above in mind, will continue to carry low chance pops
across the St. Lawrence Valley into the early evening, at which
point any lingering showers should rapidly fall apart with the loss
of diurnal heating. Otherwise, surface high pressure and upper
ridging pattern resume control of the forecast area tonight as the
weak trough will shift east to New England. SW flow will continue to
boost dewpoints overnight into the 50s. This will help to hold the
low temperatures on the mild side again with lows only dipping into
the mid to upper 50s with closer to 60 for the lake plains and urban

On Thursday we will see temperature and humidity levels edge a bit
higher as a weak warm front lifts across the region. Dewpoints will
rise into the low 60s for most with temperatures again reaching into
the upper 70s and 80s. This heat and humidity will also bring an
increased probability for shower and thunderstorms. Moisture and
lift are weak along the leading edge of this front early in the day
so have gone with a chance for showers across WNY in the morning.

Moving into the afternoon however, a shortwave trough and ribbon of
vorticity currently indicated on WV imagery over Wisconsin is
progged to arrive over Western NY, by which time CAPE values should
rise into the 400 to 1000 j/kg, with greatest instability expected
across the Southern Tier. This should trigger scattered to numerous
showers and thunderstorms during the afternoon hours with activity
working its way eastward across the forecast area through the
afternoon hours. Another area of convection will be possible across
the higher terrain east of Lake Ontario during the afternoon hours
as well, though confidence is a little lower here owing to lower
instability and possible lake shadowing. 0-6km bulk wind shear
across the forecast area is expected to remain at or below 20 kts,
so activity is expected to remain below severe levels, however with
PWATS forecast to climb above 1.5 inches, some storms could produce
heavy rain.


On Thursday night a mid level wave will push into New England. This
combined with diminishing diurnal instability will result in
diminishing showers from west to east on Thursday evening. Overnight
it will be mainly dry, although a few spotty showers or
thunderstorms still cannot be ruled out in the weak warm advection
regime, especially if any convectively generated vorticity maxima
from upstream drift into the region. The combination of boundary
layer moisture and light winds will result in patchy fog in any
areas with ample clearing. Lows will be in the mid 60s across the
Lake Plains, and lower 60s inland.

There will be a similar summer-like pattern on Friday and Saturday,
with an upper level ridge axis extending from the Mid-Atlantic to
the Lower Lakes. There will be little or no large scale ascent due
to this ridging, but moderate instability will support some showers
and thunderstorms along and inland of the lake breeze boundaries.
Areal coverage should be quite sparse, with only low chances for any
precipitation at any one given location. 850mb temps rise to around
+17C, which will support highs in the mid 80s in most areas with
upper 80s to even 90 possible from the Genesee Valley to central NY.
It will be cooler along the immediate lakeshores, especially during
the afternoon hours when the lake breeze becomes better established.

Any showers and thunderstorms will slowly diminish in coverage
during the nighttime. Again a few spotty showers or thunderstorms
cannot be ruled out if any convectively generated vorticity maxima
from upstream drift into the region. Overnight temperatures will be
warm with lows in the upper 60s across the Lake Plains and the mid
60s across interior sections.


Summers warmth will begin this period...with a slight break midweek
as both air and dewpoint temperatures will turn down a few degrees.

On Sunday the ridge of high pressure that gripped the start of the
holiday weekend will begin to weaken as a shortwave trough of low
pressure rounds the ridge over the western Great Lakes region. While
there will be chances for afternoon convection over the region
Sunday...this shortwave will likely bring the highest chances for
showers late Sunday night and Monday across the region as it

This shortwave looks to also shunt Atlantic moisture to our
east...this moisture flowing northward from tropical activity off
the Southeast states. This will allow for lowering of the humidity
if the plume of moisture remains to our east as well as a dry
period for both Tuesday and Wednesday.

High Sunday will range through the 80s...while Monday through
Wednesday will feature highs from the mid 70s to the lower 80s.


Satellite imagery indicates cloud coverage is diminishing rapidly
late this afternoon thanks to the combination of decreasing
insolation and the arrival of shortwave upper level ridging overhead
Western NY. Expect gusty winds this afternoon to diminish after
sunset with general clearing across the forecast area allowing for
virtually unlimited VFR conditions overnight.

An upper level disturbance in addition to a surface warm front will
approach the region on Thursday. This will trigger scattered to
numerous showers and thunderstorms across Western NY after 15Z, with
activity increasing in coverage around/after 18Z as the disturbance
and front move east. Greatest confidence in convection is found in
the Southern Tier, where instability will be maximized, while
confidence is lower at KBUF/KIAG where SW lake breeze flow may keep
convection limited to the east of the fields. Likewise, lake
shadowing should keep convection east of KART.


Thursday night through Monday...Mainly VFR with a chance of showers
and thunderstorms.


A ridge of high pressure will remain across the lakes tonight,
continuing mainly fair weather with breezy westerly winds. Some
isolated to scattered showers and thunderstorms will be possible
this afternoon and evening over the western end of Lake Ontario.
Winds and waves outside of any storms will remain fairly negligible
through the next few days. The tranquil pattern will continue
through the end of the week, although thunderstorms may produce
locally higher winds and waves at times each day from Thursday
through next weekend.


The first extended period of summer`s warmth will be upon us this
weekend. Temperatures will climb well into the 80s, of which some
of these daily readings may near record levels. Listed below are
the records for our three climate stations.


Friday.....May 27th...Record High Maximum...89F...1978
......................Record High Minimum...69F...1991

Saturday...May 28th...Record High Maximum...86F...2012
......................Record High Minimum...69F...1911

Sunday.....May 29th...Record High Maximum...87F...1987
......................Record High Minimum...68F...1987


Friday.....May 27th...Record High Maximum...92F...1978
......................Record High Minimum...70F...1918

Saturday...May 28th...Record High Maximum...93F...1911
......................Record High Minimum...68F...1939

Sunday.....May 29th...Record High Maximum...92F...2006
......................Record High Minimum...69F...1908


Friday.....May 27th...Record High Maximum...87F...1960
......................Record High Minimum...67F...1991

Saturday...May 28th...Record High Maximum...85F...2012
......................Record High Minimum...64F...1987

Sunday.....May 29th...Record High Maximum...87F...2012
......................Record High Minimum...63F...2006

A climatic day is between 1 AM EDT to 1 AM EDT.

Temperature records for Buffalo and Rochester date back to 1871,
while records for Watertown start in 1949.





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