Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 251825

Area Forecast Discussion
National Weather Service Buffalo NY
225 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 weak trough is draped across the forecast area this afternoon
extending from east of Lake Ontario south and west across the Finger
Lakes on to the Niagara Peninsula. Satellite and radar imagery
continue to highlight this feature with enhanced cloudiness and
isolated radar returns. An earlier push of scattered showers along
the eastern edge of the trough has now pushed east of I-81 with a
few isolated returns popping up just west of Lake Ontario at 2pm.

Mesoscale models continue to show these isolated to scattered
showers forming along near the trough at the western end of Lake
Ontario shifting south and east over the Niagara Peninsula and
perhaps into the Niagara Frontier counties where chances for showers
and thunderstorms remain into the early evening. A similar case is
also possible over the far north country and Saint Lawrence county.
Any thunderstorms that do develop will be sub-severe due to a lack
of strong wind shear. Outside of these areas a sharp cap at 925mb
observed on the 12z BUF RAOB should inhibit most, if not all,
convection south of Lake Ontario this afternoon.

Temperatures are running in the 70s for most this afternoon with the
warmer spots of Rochester and Dansville in the Genesee Valley
running in the 80s and cooler locations like Buffalo and Watertown
with westerly flow off the lakes only in the upper 60s to low 70s.

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 areas.

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.
Going into the afternoon models forecast a shortwave trough and
ribbon of vorticity crossing the forecast area where CAPE values
should rise above 1000 j/kg mainly toward the NY/PA border. Wind
shear during this time will only run about 20kts so not expecting
severe storms but have increased POPS across the Southern Tier to
likely as the best storm ingredients align in that region. More
chance range POPs extend north toward Lake Ontario.


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.


An extended period of mid summer warmth and humidity will continue
through the weekend and into early next week. The heat will peak
over the weekend, with a modest pull back in temperatures early next
week. Most days will feature a few widely scattered showers and
thunderstorms, but there will be plenty of rain free time as well.

A broad trough will remain in place over the west, with a strong
downstream ridge dominating the eastern half of the nation. High
pressure will take up residence off the southeast coast in the
classic Bermuda high location, allowing heat and humidity to pump
northward on persistent deep layer southwest flow.

The ridge will remain overhead Sunday and prevent much in the way of
large scale ascent. Diurnal instability will support widely
scattered showers and storms each afternoon and evening, especially
along and inland of the lake breeze boundaries. By late Sunday and
Monday there is some potential for an influx of Atlantic moisture as
well, associated with a weak system along the southeast coast. A
weak mid level trough will also cross the area Monday, potentially
increasing coverage and organization of showers and thunderstorms.

By Tuesday both the GFS and ECMWF 00Z runs build high pressure into
the Great Lakes with a bubble of somewhat drier air, which will
reduce the potential for any convection.


Widespread VFR conditions will continue to prevail into tonight with
general ridging of high pressure overhead. A weak trough draped
across the area could bring some widely scattered convection this
afternoon across the Niagara Peninsula which may move near KIAG and
the Saint Lawrence Valley but the vast majority of the region will
be rain free through the overnight period.

On Thursday, while a low chance of a shower is possible in the
morning along a warm front shifting over the region, better chances
of showers and thunderstorms develop especially going into the
afternoon hours as instability and moisture build. Most of this will
occur past 18z so only have VCSH in the western TAFs for now. Any
reductions below VFR would occur within convection again beyond the
current TAF period but the more likely area of storm coverage looks
to run across the Southern Tier counties.


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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