Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 220810

Area Forecast Discussion
National Weather Service Buffalo NY
410 AM EDT FRI JUL 22 2016

Very warm temperatures and high humidity levels will remain with us
through today, with the unstable atmosphere producing scattered
thunderstorms across the region. Tonight a weak cold front will drop
across the region and while it will not lower day to day temperature
values, it will noticeably lower humidity values. The next chance
for widespread convection will arrive Sunday night and into Monday.


A weak cold front lies across the Upper Great Lakes this morning,
separating a very warm and moist airmass (dewpoints in the upper 60s
and lower 70s) to the east, and a slightly cooler, but notably
drier (dewpoints in the 50s) airmass to the west.

This very warm and moist airmass will remain over our region through
the course of today. Air temperatures will rise into the mid 80s and
lower 90s across the region, which combined with oppressive dewpoint
values in the lower 70s will create apparent temperature values in
the 90s for most, and upper 90s across the Genesee Valley and Finger
Lakes region. While interior locations will be hot today, a
southwest wind off Lake Erie and also off Lake Ontario will likely
keep inland locations of metro Buffalo and northern Jefferson County
in the mid to upper 80s.

The airmass will remain unstable today with MUCAPE values ranging
between 1500 and 2500 J/KG. There will be moisture, with sfc
dewpoints over 70F and PWATS likely over 1.5 inches. Lift will be
limited, this from subtle features this morning that will be needed
to overcome a weak capping inversion near 700 hPa. Outflow
boundaries from upstream convection, and lake breezes may produce
enough lift for thunderstorms today, with the cold front later this
afternoon again possibly triggering scattered thunderstorms. Bulk
shear values in the 0-6 km layer of 35 to 40 knots will sustain
thunderstorm development, with any storm possible producing gusty
winds through the day today. The limiting factor for storm
development today will be dry air in the 850 to 500 hPa layer. Both
the GFS and ECMWF bring substantial dry air within this later across
WNY, and most of the Eastern Lake Ontario region that thunderstorm
development today will only be in the scattered category, this
despite the impressive CAPE and thunderstorm index values.

As the cold front drops across the region this afternoon and
evening, scattered convection will be pushed southeastward, with a
slightly cooler, and drier airmass following. There may be some
patchy fog in the Southern Tier tonight, this over any wet ground
from daytime storms. Otherwise the drier air should preclude fog
development overnight. Lows tonight will drop back into the mid 60s
to around 70 with dewpoints falling back into the lower 60s.


Saturday will be another hot and dry day for most of the area with a
broad ridge of high pressure across most of the CONUS extending into
Western New York. This will result in abundant sunshine in most
areas with high temperatures in the upper 80s to around 90.
However, there will be an upper level trough across New England,
with a distinct vort max forecast to drop across the Saint Lawrence
Valley on Saturday afternoon. There is a good chance for
thunderstorms across the St. Lawrence Valley and into the North
Country when considering the favorable diurnal timing and the energy
from the shortwave. This is reflected by the good consensus among
model QPF guidance. Often the dynamic forcing from a dynamic
shortwave can spark a few strong thunderstorms. SPC is carrying a
marginal risk for severe thunderstorms, and with this in mind will
add enhanced wording to the ZFP and a mention this potential in the

This shortwave will also shift winds to the northwest and advect
slightly cooler and drier air late in the day Saturday. There should
not be any weather with this, with dry weather on Saturday night as
high pressure expands into the entire region. Temperatures will be
cooler with lows ranging from the upper 50s to mid 60s.

Sunday should be mainly dry with upper level ridging across the
region. An isolated thundertorm cannot be ruled out across the
Western Southern Tier Sunday afternoon, with mostly sunny skies in
most other areas. It should feel a bit more comfortable with drier
air and slightly cooler temperatures in the 80s.

On Sunday night, a mid-level wave/warm front will approach in
advance of the next shortwave. This will provide the focus for some
thunderstorms, with increasing chances on Sunday night. Most model
guidance forecasts some QPF with this, but this is probably from
sparse convective storms which may provide only localized drought
relief. An increasing southerly flow should result in warm overnight
temperatures, especially across the lake plains where temperatures
may only drop into the lower 70s.


Model consensus continues to bring an upper-level shortwave across
the Great Lakes on Monday. This trough will drive a surface cold
front across our forecast area with renewed chances of showers and
thunderstorms. Southwest winds ahead of the front will increase
humidity levels with dewpoints again pushing toward the 70 degree
mark. The combination of heat and humidity with frontal timing
working with the diurnal heating cycle could lead to an unstable
environment for storms to work with. GFS forecast SBCAPE of 1000-
2000 j/kg and 0-6km bulk shear increasing to 30-35 kts may even
support the risk for a few strong to severe storms if these levels
or higher can be reached. High temperatures are expected to reach
into the mid to upper 80s ahead of the front with 850mb temperatures
forecast to build toward +20C.

The front will push east Monday evening with chances of showers and
thunderstorms tapering off west to east. Temperatures will remain on
the mild side overnight as humidity will be slow to scour out behind
the front. Modified continental polar air building in with high
pressure behind the cold front should lead to a string of mainly dry
days Tuesday through Thursday with more comfortable temperatures
running closer to but still a touch above 30-year normal levels.
Humidity levels will also be a touch more comfortable but still
noticeable with dewpoints hovering around 60. High temps should run
in the upper 70s to low 80s with overnight lows ranging through the
60s. Have included a slight chance for showers on Thursday with a
weak mid-level wave to the west.


VFR flight conditions will remain through a good portion of this TAF
cycle. A small area of thunderstorms now brewing over northern
Georgian Bay will likely drop SEward across WNY, with the likeliest
TAF sites impacted being KBUF/KIAG this early morning between 10 and
14Z. This activity may reach KROC and KJHW, but certainty is lower
and will include a VCTS for now. Increasing moisture this morning
may bring MVFR CIGs across the Southern Tier.

Storms may blossom again this afternoon, this with the increase of
daytime heating and instability. These storms are likely across the
Genesee Valley and Eastern Lake Ontario region (KROC/KART) and will
depend upon where the initial round of thunderstorms track. There
will be too much uncertainty for now to include any definite
weather holders in the TAFs.

A weak cold front will cross the region tonight and this will clear
the region of storms, and humidity. Expect clearing skies tonight,
with VFR flight conditions within the lowering humidity values,
except for the Southern Tier where some localized fog may form,
which would include near the KJHW terminal.

Saturday and Sunday...VFR.
Sunday night and Monday... Mainly VFR with a chance of showers and
thunderstorms and associated brief MVFR/IFR.
Tuesday... VFR.


Southwest winds will remain across the lakes and rivers today, with
winds over Lake Erie nearing 20 knots. This wind, combined with
waves of 3 to 5 feet will continue the Small Craft Advisory for Lake
Erie and the Upper Niagara River today.

As a weak cold front passes the lakes later this afternoon and
evening winds will veer slightly, and diminish in speed.

High pressure will then follow with waves and winds likely remaining
below SCA through the weekend.

The next front, with associated showers and thunderstorms and
increased winds, will move through early next week.


NY...Beach Hazards Statement from 8 AM EDT this morning through
     this evening for NYZ010-019-085.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LEZ020-



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