Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 220227
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1027 PM EDT Thu Mar 21 2019

.SYNOPSIS...
A complex storm will bring mainly rain to the region overnight.
As this storm intensifies across New England, colder air will pour
into our region and change the rain over to snow on Friday.
Snow amounts will vary, with the greatest amounts across higher
terrain and east of Lake Ontario. Snow will end from west to
east Friday night and early Saturday morning when the storm
system exits into eastern Canada.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
Regional radars and surface observations late this evening show
rain spreading into the eastern Lake Ontario region with some
scattered showers west of this.

Winter Storm Warnings were issued for east of Lake Ontario
where rain will change to snow starting across higher terrain
shortly after midnight, with a more widespread transition to
snow on Friday. A Winter Weather advisory was issued for Wayne
and Northern Cayuga counties starting late Friday afternoon
following the changeover to snow. The most significant snow for
these areas is expected on Friday night.

A closed mid-level low across Virginia will make its way to the
coast, which will combine with Atlantic moisture and energize a
surface low developing near Delaware. Meanwhile another
shortwave which is digging across the Great Lakes region
tonight will dive southeastward and merge with this system
across southern New England on Friday. Mid- level warm air
advection and upper level troughing will back into our region
overnight, with the steadiest precipitation east of Lake Ontario.
Precipitation will become more widespread in all areas late
tonight with the arrival of the second shortwave which will
provide deeper moisture and lift.

Dynamic cooling will push thermal profiles to at or below
freezing resulting in a change over to snow across some higher
terrain overnight (mainly in Lewis County). Overall snow totals
tonight will be localized, with up 2 inches by daybreak on the
higher terrain east of Lake Ontario.

During the day Friday the deep Atlantic moisture over New England
and southern Quebec will fold westward back over our region as the
second upper level low drops by our region just to the west. This
abundant moisture in the lower levels, combined with deepening cold
air and increasing low level lapse rates will result in lake
enhanced, and upslope snow showers through the day across WNY, and
then shifting eastward to areas east of Lake Ontario. This second
wave of snow will have greater accumulations than the snow
originating with the initial coastal low and shortwave. Also this
second wave of snow will have higher snow to liquid ratios...and
allow the increasing winds to create blowing snow.

Temperatures aloft at 850 hPa will drop to around -7 to -10C...not
quite cold enough for pure lake effect snow...but cool enough that
we should still see some enhancement. The moist, northwest flow will
also generate orographic lift snow Friday and into Friday night.
While accumulations will be minor through the first half of
Friday...the deepening cold air and increasing northwest winds will
begin to increase the snow accumulation Friday afternoon across the
higher terrain...and then everywhere by sunset Friday night. This
period of late Friday to Friday night is when the bulk of the snow
for this event will fall.

Winds... Winds overnight will be light across the region, with
an inverted surface trough extending across our eastern zones
from the passing coastal low. Once the surface low passes by our
latitude, a northwest wind will rapidly increase Friday midday
through Friday night. Gusts will generally be 30 to 40 mph, with
occasional gusts to 45 mph along the southern shoreline of Lake
Ontario.

Temperatures...Lows tonight will remain just above freezing for much
of our CWA. The airmass will warm a little Friday morning before the
coastal low passes by to our east, and a much colder airmass invades
the region from the northwest. Temperatures will likely begin to
fall through the afternoon hours, and continue to fall Friday night
with overnight lows in the upper teens across the higher terrain and
lower 20s near the Lakes. The combination of winds and temperatures
will make wind chill values drop into the single digits across the
region Friday night.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
The upper level pattern early in the weekend will feature a ridge
over the plains with a departing low over the northeast.  Overhead
Saturday, there should be fairly rapid drying throughout the
atmospheric profile from west to east, resulting in dry (but breezy)
weather for WNY, and snow quickly tapering off east of Lake Ontario.

By Sunday, a shortwave ridge will be overhead with a corresponding
area of surface high pressure moving east into the Mid Atlantic
states.  A cold but relatively east-west dry cold front will be
approaching from the north, but it shouldn`t arrive until after
dark.

Sunday night and Monday, the above noted front should move south
through the region, while a wandering weak system somewhere over the
plains, nearly lost in the upper level prevailing ridge, tries to
gin up some moisture for the front. The 12z GFS and ECMWF runs have
been sparse with precipitation, without enough moisture for much
more than snow showers/flurries. Will keep a chance in the forecast
until we get a little more confidence on whether we should trend
higher or lower with any precipitation.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
An upper level ridge will build across the northern Rockies and help
push an upper level trough into the Canadian Maritimes Monday night.
Cold air advection will be taking place across western and north
central NY through Tuesday with 850mb temperatures falling to -15 to
-10C. Although dry, winter-like temperatures are likely Monday night
through Tuesday night. The core of the cold air will retreat into
eastern Canada by mid-week while the upper level ridge flattens as
it moves across the Great Lakes and eastern U.S. Surface high
pressure will persist across the eastern third of the Lower 48
through Thursday and dry conditions are likely. A southerly flow
will allow temperatures to climb back to seasonal temperatures for
the last week of March.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Low level moisture will gradually increase, with cigs lowering
into the MVFR flight category or lower overnight. Late this
evening, there is an area of lower cigs and fog east of Lake
Erie which is likely to spread into KJHW but remain just south
of KBUF.

A shortwave will arrive late tonight and Friday, which will
shift winds to the northwest and provide colder air aloft. This
flow will increase low moisture and upsloping with cigs
lowering to around 1 kft. It also will change over rain to snow
roughly mid-day. Flight conditions should average in the IFR
flight category for most of Friday afternoon, but they will vary
with the snow intensity.

Outlook...

Friday night...Mainly IFR in snow and low cigs.

Saturday...Early improvement to VFR/MVFR with lingering snow
showers to the east tapering off.

Sunday...VFR.

Sunday night and Monday...VFR/MVFR with a chance of rain and
snow showers.

Tuesday...VFR.

&&

.MARINE...
A secondary low along the eastern seaboard will rapidly
strengthen overnight and Friday along the New England
coastline. This system will bring gusty west to then northwest
winds across the lakes Friday and Friday night, with building
waves. Small Craft Headlines were issued for most of the
waters, starting on Friday and lasting into Sunday for some
areas on Lake Ontario. High pressure will briefly build across
the region Sunday and Monday with improving boating conditions.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Storm Warning from 5 PM Friday to noon EDT Saturday for
     NYZ006-007.
     Winter Weather Advisory from 5 PM Friday to 8 AM EDT Saturday
     for NYZ004-005.
     Winter Storm Warning from 2 AM Friday to noon EDT Saturday for
     NYZ008.
MARINE...Small Craft Advisory from 11 AM Friday to 5 AM EDT Saturday
         for LEZ040-041.
         Small Craft Advisory from 11 AM Friday to 5 AM EDT
         Saturday for LOZ030.
         Small Craft Advisory from 11 AM Friday to 8 AM EDT Sunday
         for LOZ043-044.
         Small Craft Advisory from 11 AM Friday to 11 PM EDT
         Saturday for LOZ042.
         Small Craft Advisory from 2 PM Friday to 8 AM EDT Sunday
         for LOZ045.

&&

$$

SYNOPSIS...Thomas/Apffel
NEAR TERM...Apffel/Thomas
SHORT TERM...HSK/Zaff
LONG TERM...HSK
AVIATION...Apffel
MARINE...Apffel/Thomas



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