Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 281513
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1013 AM EST Mon Nov 28 2016

.SYNOPSIS...
Surface high pressure from Southern Quebec to the Mid Atlantic will
provide partly sunny skies and dry weather as it slowly moves east
of the Lower Great Lakes today. A deep Low pressure system over the
Upper Midwest will move a warm front across the Lower Great lakes
bringing milder air and rain tonight into early Tuesday. Another
round of unsettle weather is expected Wednesday through the end of
the week with rain and snow showers.

&&

.NEAR TERM /THROUGH TONIGHT/...
Surface analysis shows a deep low pressure system over the upper
Midwest and a surface high extending from Southern Quebec to the Mid
Atlantic. This surface high will gradually move east of the Lower
Great Lakes over the course of the day today. As this occurs, expect
increasing mid and high level clouds from west to east across the
region as the deep low pressure system over the Midwest nudges a
warm front towards the Lower Great Lakes. Additionally, as the warm
front begins to near the region southeasterly flow will also
gradually pick up in response to a tightening pressure gradient.
With respect to temperatures today, highs will peak in the upper
40s to around 50F across western NY with low to mid 40s for the
North Country.

Tonight, a nearly stationary vertically stacked mid-level low over
the Northern Plains will become occluded and push its attendant
front east across our region. The front will be accompanied by a
strong low level jet which will force a band of rain across our
region late. Basin average rainfall amounts from this will range
from a quarter to a third of an inch, with some potential for
localized amounts of up to a half inch. The strong warm advection
ahead of this front will bring a non-diurnal temperature trend
tonight. It is expected that any near or below freezing temperatures
confined to the Saint Lawrence Valley should warm above freezing
before rain arrives.

The strong 50-60kt 925mb low level jet will also bring a short-lived
downslope flow wind event along the Chautauqua/ Southern Erie county
shoreline late tonight. These winds will ride over the top of the
higher terrain in the Southern Tier beneath an inversion then be
forced down along the immediate Lake Erie lakeshores with winds
gusts of up to 50 mph. The one factor which should prevent higher
gusts is that the flow is not quite perpendicular to the Chautauqua
Ridge. Have added a Wind Advisory to Chautauqua and Southern Erie
counties to cover for these gusty winds along the lake shores.
Elsewhere wind gusts should not be nearly as high as a steep
inversion will keep gusty winds from mixing to the ground.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
A vertically stacked and elongated low stretching from Minnesota to
Lake Superior will spin in place Tuesday. Meanwhile a strong
southern stream shortwave will rotate through the base of the closed
low and phase with it, pushing a warm occluded front east across our
area. The main forcing will be associated with strong convergence
and moisture transport near the nose of a very strong 70+ knot
southwesterly low level jet. Model guidance continues a faster trend
with this system since yesterday, with rain early in the day across
the eastern Lake Ontario region and Central NY quickly ending by
late morning. Farther west, it should already be dry at 7AM across
Western NY.

Otherwise expect a fair amount of clearing across the lake plains of
Western NY on Tuesday as a dry slot in the wake of the warm occluded
front moves into the Lower Great Lakes. Clouds may be more stubborn
to clear east of Lake Ontario until late in the day. The combination
of clearing skies, SSW downslope flow, and arrival of a warmer
airmass will allow temperatures to soar, with many lower elevations
across Western NY and the Genesee Valley reaching the lower 60s. A
southwest flow off Lake Erie will likely keep the immediate Buffalo
area in the 50s.

Downslope winds will be ending by 7AM Tuesday along the Lake Erie
shore as boundary layer flow becomes more southwesterly and less
perpendicular to the terrain, and the stable layer of air near the
ridge tops is removed by the passage of the warm occluded front.
Downslope winds may also develop briefly in the lee of the Tug Hill
Plateau across the Black River Valley with a few gusts to around 40
mph Tuesday morning. Otherwise winds will diminish Tuesday afternoon
as the low level jet moves east, and the pressure gradient relaxes.

Tuesday night our region will be between systems, with dry weather
and some partial clearing to start the night. The upstream closed
low over the Upper Midwest will begin to dig again, and force a wave
of low pressure to develop over the Ohio Valley. Increasing warm
advection ahead of this system will bring an increase in clouds from
southwest to northeast overnight, with a few showers possibly
entering Western NY late.

Wednesday and Wednesday night the closed low will slowly advance
into the Central Great Lakes, with the wave of low pressure moving
from the Ohio Valley to New England. Differential temperature
advection and frontogenesis associated with the wave of low
pressure, and DPVA ahead of the approaching trough will bring
another period of rain showers to the region Wednesday and Wednesday
evening. Temperatures will still be very mild Wednesday with highs
in the 50s, before a cold front crosses the area Wednesday evening
with cooler air beginning to filter back into the Lower Great Lakes.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
A ridge will persist through the period across the North Atlantic,
well east of Greenland. Meanwhile an omega block will develop across
Central Canada. This will allow a fairly deep trough to remain in
place across Quebec and the Canadian Maritimes, keeping the Great
Lakes region and New England on the southern edge of colder air.
This will keep temperatures near seasonal normals for late November
and early December, temperatures right near the threshold between
rain and wet snow.

This period will be chilly and unsettled with scattered rain and
snow showers from Thursday night through next weekend. The pcpn will
be driven by a parade of relatively weak systems moving around the
trough over Quebec that will keep a moist cyclonic flow in place
over the Lower Great Lakes. Local lake influences will enhance the
showers east of the lakes so that generally insignificant snow
accumulations will be possible, with any accumulations likely
limited to higher elevations given the marginal temperatures
surface and aloft for snow.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
Areas of patchy fog east of lake Ontario will continue to produce
MVFR VSBYS at a few locations late this morning. This fog will
slowly dissipate through the rest of the morning hours.
Otherwise, with surface high pressure from Southern Quebec to the
Mid Atlantic expect mainly VFR conditions for the rest of today
despite an increase in mid and high level clouds. In addition to
the increase in cloudiness southerly flow will begin to pick up
across the region.

Tonight, Low pressure over the upper Midwest will send a warm
front towards the Lower Great lakes. Expect Cigs to thicken and
lower, along with wind gusts picking up across western NY between
02-04z Monday. A strong low level jet and light to moderate rain
will accompany the warm front across western NY about 06-12z. Cigs
should remain at VFR except at KJHW where IFR is possible around
the time rain arrives. Surface gusts to around 25kts should not
bring much of a LLWS concern despite winds of 40-50kts at 2000ft.

Outlook...
Tuesday...MVFR/IFR in spots improving to VFR.
Wednesday...MVFR/IFR with another round of widespread rain.
Thursday and Friday...VFR/MVFR with a chance of lake effect
rain/snow showers.

&&

.MARINE...
Winds will turn southeast and increase ahead of the next storm
system today and tonight. Nearshore waters of Lake Erie will see
near 30 knots with 20-25 knots along the nearshore waters of eastern
Lake Ontario tonight into Tuesday morning has required a Small Craft
Advisory even as the higher wave heights will mainly be confined
across the northern lake shores.

Winds will subside later Tuesday behind the warm front. A cold front
will cross the region Wednesday night with winds and waves likely
increasing again and another round of marine headlines needed into
Thursday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Wind Advisory from 1 AM to 7 AM EST Tuesday for NYZ019-085.
MARINE...Small Craft Advisory from 7 PM this evening to 10 AM EST
         Tuesday for LEZ040-041.
         Small Craft Advisory from 10 PM this evening to 1 PM
         EST Tuesday for LOZ043>045.

&&

$$

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



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