Forecast Discussion

Forecast Discussion for BUF NWS Office
000
FXUS61 KBUF 201750
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
150 PM EDT Thu Sep 20 2018

.SYNOPSIS...
A warm front will gradually lift north across the central Great
Lakes today then New York tonight. The greatest chances for some
rain showers will be across Lake Ontario and the Saint Lawrence
River Valley tonight. Friday will be quite unsettled as a powerful
storm system moving into Quebec will generate strong winds across
parts of our region. A cold front associated with this storm system
will not only introduce a much cooler airmass for the weekend...but
it could also generate strong thunderstorms as it moves through late
on Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Satellite late this morning shows leftover low stratus across the
inland Southern Tier and portions of the Niagara Frontier starting
to lift and scatter out. Otherwise, a warm front associated with
strengthening low pressure over the Central Plains will lift north
across Ohio Valley today. Areas seeing sunshine late this morning
will see it fade behind mid and upper-level clouds moving in from
the west, however expect it to remain dry through the day, as any
shower activity will remain to the west and southwest where the
better forcing and moisture exist. Some warm advection aloft will
support a touch warmer and more humid day than yesterday under
southeast flow. Highs will be in the mid to upper 70s with dewpoints
across much of western NY rising back into the low 60s.

Tonight, the surface low will shift northeast across Minnesota and
Lake Superior while its warm front will lift northeast across the
Central Great Lakes and New York state. The best forcing and
moisture will remain closer to the center of the storm while
warm/moist advection will likely produce some showers across and east
of Lake Ontario late with a slight chance for a shower over the
Niagara Frontier. Otherwise mainly dry and cloudy conditions are
expected overnight. Lows will be more milder tonight with the
increase in dewpoints only allowing for temps to fall into the mid
to upper 60s across Western NY, and upper 50s to lower 60s east of
Lake Ontario. A tightening pressure gradient as the surface low well
to our west deepens will support increasing surface winds.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
Friday will be active across the region, with advisory level wind
gusts expected northeast of Lake Erie, and the potential for severe
weather during the late afternoon and evening.

Synoptic Setup...low pressure will move from just northeast of Lake
Superior Friday morning to central and northern Quebec by Friday
evening, with a trailing strong cold front crossing our region
Friday evening. Large scale ascent and deep moisture will increase
by late afternoon in advance of the longwave trough, with a belt of
50-55 knot flow in the 900-700mb layer supporting strong moisture
transport and increasing low level convergence. Boundary layer
moisture will be ample as surface dewpoints surge into the upper
60s.

A few showers may still linger early in the morning across Western
NY, and through midday east of Lake Ontario, supported by another
weak warm frontal segment and a weak mid level shortwave. Following
these potential morning showers, expect the bulk of the day to be
rain free. By mid to late afternoon a line of thunderstorms will be
developing just upstream across southern Ontario. There may also be
a few scattered showers and storms developing on the convergence
zone driven by lake and terrain influences from the western Southern
Tier into the western Finger Lakes and points southeast of Lake
Ontario. The main line of showers and scattered storms will then
quickly cross the region from northwest to southeast Friday evening.

Winds...A strong 55 knot low level jet will cross the region in the
warm sector Friday. Weak warm advection and general weak synoptic
scale ascent will prevent the full mixing of these higher momentums
from aloft to the surface. That said, low level lapse rates will
still steepen sufficiently to produce gusty winds areawide. The
strongest winds by far will be found across the Niagara Frontier,
where channeling down Lake Erie typically produces stronger gusts.
Expect gusts of 50-55 mph from midday through the afternoon. With a
wind direction of 220-230, the highest gusts are likely to be in
Niagara County. Elsewhere across the rest of the region, expect peak
gusts to run in the 30-40 mph range. The winds will quickly diminish
by early evening as the low level jet begins to move east of the
area, and the boundary layer begins to stabilize.

Severe Weather...Deep layer shear profiles will be strong and very
much unidirectional given the strong 55 knot low level jet in place.
Warm mid level temps and poor mid level lapse rates will temper
instability somewhat, but still expect SBCAPE to rise to 500-
1000J/kg by afternoon. The combination of unidirectional shear
profiles and linear forcing should promote upscale growth into line
segments with attendant risk of damaging winds.

Temperatures...It will be very warm on Friday, with highs in the mid
to upper 80s across the lower elevations away from lake influences,
and low 80s across higher terrain and east of Lake Ontario. SSW
winds will keep areas near the Niagara River and Saint Lawrence
Rivers a little cooler. Surface dewpoints in the 65-70 degree range
will give a muggy feel.

Following the frontal passage later Friday evening, the rain will
quickly end from northwest to southeast. A few scattered light lake
effect rain showers may develop late Friday night into early
Saturday morning south of Lake Ontario as cold air deepens, but this
will not amount to much. Lake effect and upslope clouds will
continue Saturday morning, with slow clearing from north to south
Saturday afternoon as dry air and subsidence over southern Ontario
moves into the area. High pressure will then bring dry and mainly
clear to partly cloudy conditions Saturday night through Sunday
night. A cold front moving into Ontario and Quebec will wash out to
the north of our area Sunday, bringing little more than a modest
increase in sky cover.

Temperatures will be much cooler over the weekend. Expect highs in
the lower 60s across lower elevations and mid to upper 50s on the
higher hills Saturday. Highs Sunday will be in the mid 60s across
lower elevations. Lows Saturday night and again Sunday night will
drop into the mid to upper 40s away from the immediate lakeshores,
with upper 30s to lower 40s east of Lake Ontario.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
Monday surface high pressure will slide to our east, allowing for a
return flow of warmer...but more moist air. This surface high should
maintain a dry day Monday, but by Monday night rain showers
associated with a warm front will lift northward across mainly WNY.

Tuesday and Wednesday another cold front will advance towards our
region...this from a surface low tracking across central Ontario and
Quebec. Tuesday will feature warmer temperatures, into the lower
70s...with chances for mainly afternoon showers and thunderstorms.
Activity will likely be a little more widespread on Wednesday as a
cold front is forecasted to cross the region. Highs Wednesday ahead
of the cold front will again reach into the low to mid 70s.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Leftover IFR stratus across the inland Southern Tier (KJHW), and
MVFR stratus across portions of the Niagara Frontier (KIAG) will
lift/burn off by early afternoon.

Later today, a warm front will gradually push to the north across
the Ohio Valley. This will be responsible for a west to east
increase in VFR low and mid level clouds across the state, while any
showers should stay north and west of the border.

Tonight, the warm front will lift northeast across Lake Ontario and
New York state. Guidance indicates that widespread stratus will
spread northwest from PA reaching into portions of the western
Southern Tier and mainly the higher terrain east of Lake Ontario.
All TAF sites however, will remain just west/north of this low
stratus with VFR expected. Showers along the warm front will become
likely east of Lake Ontario tonight, with lesser chances as you head
further south.

Outlook...

Friday...VFR/MVFR. Showers likely with a chance of
thunderstorms. Windy with strong thunderstorms possible.
Saturday...Mainly VFR. A chance of showers.
Sunday and Monday...VFR.

&&

.MARINE...
A warm front will approach later today with an uptick in southeast
to easterly flow. This will be modest with the exception of western
Lake Ontario where a 15 knot flow will result in choppy conditions
by later this afternoon.

A deep storm system over Lake Superior tonight will track across
Ontario into Quebec on Friday. As a result, southwest winds will
freshen across the Lower Great Lakes with 30 knot winds anticipated
on Lake Ontario. Fairly widespread small craft advisories can be
expected late tonight through Friday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Wind Advisory from 11 AM to 8 PM EDT Friday for NYZ001-002-010-
     011.
MARINE...Small Craft Advisory from 6 AM to 11 PM EDT Friday for LEZ020.
         Small Craft Advisory from 2 AM Friday to 8 AM EDT Saturday
         for LEZ040-041.
         Small Craft Advisory from 6 AM to 11 PM EDT Friday
         for LOZ030.
         Small Craft Advisory from 6 AM Friday to 2 PM EDT Saturday
         for LOZ042>044.
         Small Craft Advisory from 4 AM Friday to 8 AM EDT Saturday
         for LOZ045.

&&

$$

SYNOPSIS...RSH/Smith
NEAR TERM...JM/Smith
SHORT TERM...Hitchcock
LONG TERM...Thomas
AVIATION...JM/Smith
MARINE...JM/Smith

NWS BUF Office Area Forecast Discussion