Area Forecast Discussion
Issued by NWS Buffalo, NY

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370
FXUS61 KBUF 202346
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
746 PM EDT Sat Apr 20 2019

.SYNOPSIS...
A slow moving low pressure system will move to the Mid Atlantic
region by Sunday evening. Showers overnight will taper of to just
scattered showers by Sunday. Temperatures will remain at or a little
above normal into early next week.

&&

.NEAR TERM /THROUGH SUNDAY/...
There`s still some instability over the Southern Tier this evening
on the other side of a warm front, but a cooler airmass to the north
along with a stout inversion is providing much more stability to the
north.  A narrow corridor of elevated weak elevated instability also
extends across central NY and into eastern Lake Ontario. A few more
thunderstorms are possible in the above mentioned areas, with a
slightly higher threat for some cloud to cloud and cloud to ground
lightning near the PA border.  Instability trends will diminish into
this evening with the loss of isolation despite steep lapse rates
aloft courtesy of the cold pool from the upper level low over the
Upper OH valley. Thus expect fewer showers with time over the
region. Low levels remain moist allow for the redevelopment of
patchy fog.

The upper low will slowly meander to the east during Sunday
eventually reaching the Mid-Atlantic region Sunday. Colder air
underneath the upper low will allow for enough instability to keep
the potential for scattered showers going through the day Sunday.
Flow aloft looks fairly weak, so any convection that does develop
could produce local downpours.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
Sunday night and Monday the center of the cutoff upper level low
will slowly drift from the Mid-Atlantic states to a bit southeast of
Long Island...with an associated lingering upper level trough axis/
deformation zone sliding from Lake Ontario into New England. Lingering
forcing and moisture along this latter feature could produce a few
additional widely scattered showers along our southeastern periphery
Sunday night and across interior portions of the North Country on
Monday before finally exiting our region to the east...with otherwise
dry and quiet weather expected. Temperature-wise...lows Sunday night
will mostly be in the lower to mid 40s...with highs away from lake
influences then rebounding into the mid and upper 60s on Monday as
our airmass warms aloft in the wake of the departing upper low.
Closer to the lakes the weak pressure gradient and light background
synoptic flow will allow for the development of solenoidal lake
breeze circulations as the day progresses...which will in turn help
to keep things cooler along and a bit inland from the lakeshores.

Monday night our region will lie under the influence of a weak bubble
of high pressure...while low pressure develops into the Central Great
Lakes and drives a warm frontal boundary across southern Canada. With
the latter remaining north of our region...we can expect a dry and
tranquil night with lows mainly in the mid to upper 40s.

On Tuesday the aforementioned wave of low pressure will make its way
northeastward across Lake Huron to the Ontario-Quebec border...while
pivoting its trailing cold front to roughly our western doorstep
by about sunset. With this system trending a bit slower in the 12z
guidance...it now appears that our area should remain mostly dry
through early afternoon...before the approaching front and increasing
height falls/DCVA aloft bring about an increasing likelihood of showers
from northwest to southeast through the rest of the daylight hours.
With the slower progression of the front also allowing for more
daytime insolation/heating and the corresponding development of
sufficient instability at both the surface and aloft...there should
also be a general chance of thunderstorms...and have therefore bumped
thunder probabilities up into the chance range areawide. Coupled with
850 temps surging to between +9c and +13C out ahead of the front and
an increasing southwesterly flow...the increased heating should
also allow for high temperatures to surge into the lower to mid 70s
away from any lake influences...so have bumped these up significantly
from our previous continuity.

Tuesday evening the surface low will track across southern Quebec
while easing its cold front across our region...with the frontal
passage generating a high likelihood of showers and the potential
for some scattered embedded thunderstorms areawide. Diminishing
forcing and moisture behind the departing boundary should then lead
to diminishing shower chances later Tuesday night and Wednesday...
with cool air advection in its wake also resulting in temperatures
settling back to right around seasonal normals by Wednesday.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
While a progressive split flow will still be in place at the start
of this forecast period...a phasing of the branches over the
eastern third of the country is suggested by the bulk of medium
range ensemble members. Fortunately there is not enough
amplitude in the pattern to make this phasing very significant.
This should render the occasion as fairly benign with nothing
more than a complex frontal passage Friday. Outside of this
event...our region will really have little weather to deal with
while temperatures will average close to...or just a bit above
late April norms.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
IFR or lower flight conditions will be widespread overnight north of
a warm frontal boundary over the Southern Tier counties, with VFR
conditions south of the boundary.  IFR and some LIFR CIGS will last
the longest across the Niagara Frontier with some fog possible near
the lakeshores and in other sheltered regions. Scattered showers
will continue to move north into the region this evening but with a
weakening trend with time. There is a low chance for thunder across
central New York in area of better instability with more cloud
breaks, but confidence in actual timing and location is low,
therefore will not include in TAFs.

Outlook...

Sunday...IFR slowly improving to VFR in the afternoon.
Monday...VFR.
Tuesday through Thursday..Mainly VFR with a chance of showers.

&&

.MARINE...
Winds and waves continue to decrease light northerly or variable
winds becoming light SW on Sunday.  Slow moving showers from the
south will slowly end overnight.  Sub small craft advisory
conditions will then last well into next week.

&&

.EQUIPMENT...
The KBUF WSR-88D radar will be down most of next week for a
scheduled upgrade. The radar will be down beginning Monday morning
April 22, with a planned outage lasting 5 days until Friday April
26.

During the upgrade, the transmitter will be refurbished including
the installation of new fuses and cables. Some of the components
being replaced are original to the radar, which is now over 20 years
old. The transmitter refurbishment is the second major project of
the NEXRAD Service Life Extension Program, a series of upgrades and
replacements that will keep our nation`s radars viable into the
2030`s.

This is the second project in the NEXRAD Service Life Extension
Program. The first was the installation of a new signal processor.
The last two phases of the project are the refurbishment of the
pedestal, and refurbishment of equipment shelters. All phases are
expected to be complete in 2022.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...TMA/Zaff
NEAR TERM...TMA/Zaff
SHORT TERM...JJR
LONG TERM...RSH
AVIATION...TMA/Zaff
MARINE...TMA/Zaff
EQUIPMENT...Hitchcock



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