Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 201748
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
148 PM EDT Fri Apr 20 2018

.SYNOPSIS...
Cool but largely dry weather will prevail this afternoon as low
pressure exits across the Canadian Maritimes. Expansive high pressure
will then build across the region this weekend...ushering in a welcome
period of fair dry weather and day to day warming that will last through
early next week...when temperatures will finally climb back to much more
typical springtime levels.

&&

.NEAR TERM /THROUGH SATURDAY/...
Nearly vertically stacked low pressure over the Canadian Maritimes
will continue to drift eastward and away from our region this
afternoon...while expansive high pressure and drier air slowly ridges
eastward from the Upper Mississippi Valley and Upper Great Lakes. A
lingering northwesterly upslope flow of colder air and leftover low
level moisture in the wake of the low will help to maintain a fair
amount of stratocumulus from the interior portions of the Southern
Tier northeastward across the Finger Lakes and North Country...though
at the same time the moisture will be too shallow to support much
more than a few passing flurries across the North Country. Elsewhere
there will be more in the way of sunshine...with daytime highs ranging
from the mid to upper 30s east of Lake Ontario to the upper 30s and
lower 40s across the remainder of the region.

Tonight the sprawling surface high will continue to build eastward
from the Upper Great Lakes while helping to scour out any leftover
low level moisture from west to east...thereby leading to clearing
skies and tranquil conditions. In tandem with lightening winds and
our cold dry airmass...this will set the stage for a cold night with
lows ranging from the lower to mid 20s in the normally colder interior
portions of the Southern Tier and North Country...to around 30 right
along the lakeshores.

On Saturday the core of the large surface ridge will build directly
across our area...with attendant subsidence and plentiful dry air
promoting dry weather along with mostly sunny skies...with a passing
upper level jet streak merely bringing a period of cirrus-level
cloudiness to portions of the western Southern Tier. Meanwhile the
strong April sun will help to modify our resident airmass...thereby
allowing daytime highs to recover into the mid to upper 40s across
the higher terrain and in areas of lake influences to the lower 50s
elsewhere. This will merely be the beginning of a steady day to day
warming trend that will last through early next week and will help
to finally bring temperatures back up to much more typical springtime
levels...the details of which are discussed further in the short term
section below.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
The tranquil weather continues into the end of the weekend with high
pressure across the eastern Great Lakes Saturday night and Sunday.
Clear night skies and light winds will allow temperatures to radiate
Saturday night and Sunday night. Low temperatures will drop into the
U20s/L30s both nights. A light northerly component will keep
temperatures from reaching their full potential Sunday however full
sunshine will continue the upward trend in temperatures, in the mid
to upper 50s.

High pressure moves to the east and over New England Monday. A light
southerly flow begins Monday and the combination of enhanced
subsidence, sunshine and warm air advection will allow temperatures
to climb into the 60s inland. A lake breeze will likely win out
under light southerly flow and areas along the lake shores will stay
in the 50s.

A closed upper level low will move from the TN Valley into the lower
Ohio Valley while high pressure moves off the southern New England
coast Monday night. Mid-high level clouds will increase and a light
southerly flow will keep temperatures elevated overnight, in the
U30s/L40s.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
Ongoing warm advection will allow for a continued upward trend in
temperatures, with highs likely well into the 60s on Tuesday as long
as cloud cover does not become too thick. Any showers should stay
south of the NY/PA line through late Tuesday afternoon.

Tuesday night through Thursday medium range model guidance begins to
diverge some in the track and timing of synoptic scale systems. The
GFS takes the Ohio Valley low slowly northward towards our region,
phasing it with another northern stream trough digging into the
western Great Lakes. This would bring several days of showers and
clouds from Tuesday night through Thursday. The ECMWF keeps these
two systems more separate, with the closed low moving northeast
along the eastern seaboard, as the second northern stream trough
acts more as a kicker than phasing. The ECMWF would produce a few
light showers later Tuesday night through Wednesday evening before
dry weather returns Thursday. Given the spread in model guidance,
kept POPS in the chance range through the period, peaking on
Wednesday.

Temperatures will pull back some behind this system by late next
week, but 850mb temps are still above 0C in its wake. This will
prevent any return to winter-like temperatures, with highs in the
50s still probable late next week behind the system.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Low pressure over the Canadian Maritimes will continue to drift
eastward this afternoon...while large high pressure and drier air
slowly ridges eastward from the Upper Mississippi Valley and Upper
Great Lakes. A lingering northwesterly upslope flow of colder air
behind the departing low will help to maintain a fair amount of
VFR/MVFR stratocumulus from the interior portions of the Southern
Tier northeastward across the Finger Lakes and North Country...
while the remainder of the region experiences VFR conditions under
mostly sunny skies.

Tonight the sprawling surface high will continue to build eastward
from the Upper Great Lakes...bringing clearing skies and widespread
VFR conditions. On Saturday VFR conditions will continue as the
high builds directly over our region.

Outlook...
Saturday night through Tuesday...VFR.

&&

.MARINE...
A lingering moderately brisk northwesterly flow of cold air is
still maintaining advisory-worthy winds and/or waves along the
south shore of Lake Ontario from Hamlin Beach to Mexico Bay...
however these will diminish to below advisory levels by late this
afternoon or early this evening as high pressure builds into the
region.

After that...an extended period of tranquil conditions is expected
this weekend and early next week as high pressure first builds
directly across the Lower Great Lakes...then slowly drifts off to
the east.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LOZ043-
         044.

&&

$$

SYNOPSIS...JJR
NEAR TERM...JJR
SHORT TERM...HSK
LONG TERM...Hitchcock
AVIATION...JJR
MARINE...JJR



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