Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 260616
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
216 AM EDT Mon Jun 26 2017

.SYNOPSIS...
Temperatures will continue to run cooler than average through
Tuesday, as an upper level trough moves across the region. The
cooler temperatures will be accompanied by showers at times, as a
series of upper level disturbances cross the area. The trough will
move east by Wednesday, with warmer temperatures expected by mid-
week.

&&

.NEAR TERM /THROUGH TODAY/...
A chilly airmass continues to spread into the region early this
morning with mesoanalysis showing 850mb temps have lowered to +7
over the forecast area. This is certainly cool enough to bring a
some lake effect/enhancement east of the +22C on Lake Erie and +19C
on Lake Ontario. While some widely scattered/isolated showers are
showing up on radar, expect development of scattered lake effect
showers through early this morning. Shear profiles do not look ideal
for well organized bands. An overall 260-270 degree flow will direct
the highest probabilities for showers across the western Southern
Tier/Southern Erie county off Lake Erie and Oswego county into
Southern Lewis off Lake Ontario. Lake induced equilibrium levels of
20kft+ yields a chance of thunder along with graupel possible if
some degree of organized bands can develop. Overnight lows will
again dip into the low-mid 50s and even upper 40s in the cooler
interior western Southern Tier and Tug Hill.

After sunrise, anomalously cold upper level trough will continue to
cross the Great Lakes. Another short wave looks to rotate through
the base of the trough improving overall dynamics. This feature
along with the combination of above-average lake temperatures, and
850 mb temperatures nearing +4C are almost certain to generate a
robust lake response, creating the potential for bands of rains
downwind of the lakes. Cool air aloft, clouds and rain will keep
most temperatures in the 60s.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
Monday night and Tuesday the heart of a much cooler than normal
airmass will cross the area as a potent mid level shortwave moves
through the mean longwave trough over the Great Lakes and New
England. DPVA associated with the sharp mid level vorticity maxima
will produce a few scattered showers across the region. The main
concern will be lake effect rain potential, a rarity for late June.
850mb temps will bottom out around +4C Tuesday morning. With the
lake at around 21C on average that yields more than enough lake
induced instability to support lake effect rain. These temperatures
will generate around 1800J/kg of lake induced CAPE and equilibrium
levels around 30k feet.

Off Lake Erie...expect lake effect rain showers to slowly become
better organized during the late evening and early overnight Monday
night, with lingering diurnal mixing initially hurting the chances
of organized development. By late Monday night and early Tuesday
morning expect a broken line of nearly steady state convection to
focus on the Buffalo southtowns on WSW flow, and likely hugging the
shoreline of southern Erie County and possibly into the Dunkirk
area. Given the strong instability, expect scattered thunderstorms
to be supported within this band of lake effect rain, and locally
heavy rainfall. If the band stays stationary long enough, rainfall
amounts could easily exceed 1 inch. Tuesday morning boundary layer
flow will become more westerly following the passage of the mid
level trough, forcing the lake effect rain inland across the western
Southern Tier where it will transition to diurnally driven scattered
showers by early afternoon.

Off Lake Ontario...The airmass is not quite as cold or supportive of
lake effect rain at the east end of Lake Ontario, and the lake
itself is not as warm yet. This will yield less of a lake response
compared to Lake Erie. Expect scattered lake effect rain showers
across Jefferson County later Monday night, likely peaking Tuesday
morning with an added boost of lift from the passing mid level
shortwave. By Tuesday afternoon most of the showers will move inland
and transition to diurnally driven showers

Otherwise Tuesday afternoon scattered showers will continue,
driven by some limited moisture and steep low/mid level lapse
rates beneath the cold air aloft. These will gradually end
Tuesday evening with the loss of daytime heating, with the
possible exception of the eastern Lake Ontario region where some
weak lake induced instability and more synoptic scale moisture
may still support a few showers.

By Wednesday the base of the mid level trough will swing northeast
across Quebec. This will leave the bulk of the area in a drier, and
somewhat warmer airmass as high pressure builds from the Ohio Valley
to the Mid Atlantic States. This will bring a return to dry weather
for most, with diurnal cumulus still developing with daytime heating
inland from the lakes. There may still be a few scattered showers
east of Lake Ontario in closer proximity to the departing mid level
trough.

Wednesday evening any lingering scattered showers east of Lake
Ontario will end as the trough moves farther away. Overnight clouds
will increase from west to east as fairly strong warm advection and
isentropic upglide develop ahead of low pressure moving through the
Upper Midwest. This may produce a few showers towards Thursday
morning across Western NY.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
This will be a very unsettled period across our forecast area...as
we can anticipate numerous showers and thunderstorms...including the
likelihood for some localized heavy rain. Temperatures will average
a little above normal...largely due to warm nights...while humidity
levels will climb to uncomfortable levels.

The unsettled conditions will be supported by an oscillating frontal
boundary that will straddle the Lower Great Lakes. Two distinct
surface waves will eject out of a broad...low amplitude trough over
the center of the country during this time period...with each
pushing the boundary back and forth across our region to
force/enhance the convection. The most widespread shower and
thunderstorm activity will be on Thursday in advance of the first
wave...then Friday night and Saturday as the second feature passes.

Max temperatures all four of these days will generally range from
the upper 70s to lower 80s...while overnight lows will mainly be in
the mid 60s.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
VFR remains in place early this morning with only a few isolated
showers on the radar. A cooler airmass continues to move over the
forecast area where some lake effect showers will likely develop
toward 12z before moving inland as a lake effect modifies to a lake
breeze. Associated convection should move inland during the day as a
result. Some MVFR will be possible with those showers (and
thunderstorms). Lake effect showers look to become much more
organized tonight under a southwest flow which should direct a
decently organized band of rain showers and potentially some thunder
and graupel near KBUF and maybe even KART.

Outlook...
Tuesday...Mainly VFR with scattered to numerous showers and
thunderstorms...mainly in the afternoons.
Wednesday...Mainly VFR.
Thursday and Friday...VFR/MVFR with a chance of showers and
thunderstorms.

&&

.MARINE...
Although winds have dropped off a little overnight, expect winds to
quickly pick up again after sunrise today with renewed west to
southwest winds near 20 knots, lasting through this evening along
with some lake effect showers. Waves will generally range from 3 to
6 feet on the eastern end of Lake Erie, sufficient for small craft
advisory conditions through this evening. Smaller waves are expected
on Lake Ontario.

Lighter winds will promote sub-advisory wave action on the lakes
from tonight through at least mid-week with periods of lake effect
showers over the lakes into Tuesday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 10 PM EDT this evening for LEZ020-
         040-041.

&&

$$

SYNOPSIS...TMA
NEAR TERM...SMITH/TMA
SHORT TERM...HITCHCOCK
LONG TERM...RSH
AVIATION...SMITH
MARINE...SMITH



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