Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 280553
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
153 AM EDT Tue Mar 28 2017

.SYNOPSIS...
A weak area of low pressure will cross the region today, bringing
scattered rain showers across the region, while also producing some
fog. A light northerly wind through tonight will maintain a cloudy
sky across the region, while Wednesday and Thursday should feature
mostly sunny skies. Temperatures will remain seasonable through the
week.

&&

.NEAR TERM /THROUGH TODAY/...
During this period...an initial weak low pressure center over
western Quebec will slide eastward to the Saint Lawrence
Valley...while a second weak low over the Lower Ohio Valley
makes its way eastward to the Delmarva coastline. In between...
a connecting weak surface occlusion will slide east across our
area later tonight and early Tuesday.

As a result of the above developments...we can expect two...
albeit largely separate areas of rain showers to affect our
region between later tonight and Tuesday. The first of these
will be an area of showers associated with the initial weak
surface low and adjoining portions of the surface occlusion...
which should move across the Saint Lawrence Valley and adjoining
portions of the North Country late tonight and Tuesday morning.
The other (and larger/more noteworthy) area of showers will be
attendant to the second wave passing by to our south on Tuesday...
and should pass across our southernmost two tiers of counties
during the morning and midday hours of Tuesday...before receding
off to the east during Tuesday afternoon.

With the above in mind...have generally indicated likely PoPs
for the above areas later tonight and Tuesday...with low-end
categorical values across the Southern Tier Tuesday...which will
lie closest to the track of the second low. Elsewhere...any
shower potential should be much lower and mainly confined to the
chance range.

Aside from the above...with plenty of moisture remaining in
place...skies should remain mostly cloudy to cloudy through the
period...especially later tonight and Tuesday when widespread
lower clouds should redevelop owing to a developing weak northerly
upslope flow. Owing to the moist airmass and light winds...at
least some patchy fog should also redevelop in most areas overnight
and then persist into or through Tuesday morning... though at
this point feel this should not become dense given the cloud
cover that will already be in place.

With respect to temperatures...expect readings to remain on the
mild side for late March...with lows tonight ranging in the lower
to mid 40s...and highs on Tuesday ranging in the upper 40s to
lower 50s.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
Water Vapor imagery does a great job showing what`s to come later
this week with a ridge over the SW US while a trough drops into the
Western US.  These will be the main features once the low over the
MS Valley moves east of our region by Tuesday evening.

Tuesday night and Wednesday...The west coast trough will force the
ridge to amplify and move into the central US by Wednesday.  This
will allow surface high pressure to slowly expand south through
Canada and slowly toward the Northern Great Lakes by late Wednesday.
The result will be a cool subsident airmass under a light northerly
flow.  There may be some low level moisture initially trapped near
the surface, but over time expect this to slowly mix out with the
increasingly dry airmass aloft.  Highs Wednesday will be the coolest
of the week with most locations stuck in the 40s.

Wednesday Night...Continued drying will likely allow for continued
clearing Wednesday night.  With the ridge axis nearly overhead,
radiational cooling should allow temperatures to drop below freezing
for most of the region.

For Thursday...the west coast trough by this time should have cutoff
over the desert Southwest and heading toward the lower Plains
states.  This will allow Gulf of Mexico moisture to stream northward
with warm advection underway to our south.  Slowly rising motion and
increased moisture will promote thickening clouds on Thursday ahead
of the next weak surface low.

Thursday night...This next surface low, like the last several, will
be stacked underneath it parent upper level low and not particularly
interesting in terms of overall weather impacts for the region, but
there is enough model agreement to introduce a high confidence for
eventual rain for the region Thursday night.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
The pattern will become more active again by the end of the week
after a few dry days. A mid level closed low will meander across the
Four Corners region through Tuesday, then eject ENE across the
southern Plains to the Ohio Valley by Friday. The 12Z guidance has
trended a little southward with the track of the ensuing surface
low, but still more than close enough to bring another period of wet
weather to our region. Rain will begin to overspread Western NY
Thursday night, then spread across the rest of the area by Friday
morning as the closed low and surface low move into the Ohio Valley
and spread large scale ascent and moisture transport into our
region. Periods of rain then continue Friday and Friday night as the
system moves slowly towards the Mid Atlantic states. With the
farther south low track, the rain may start as a period of wet snow
across the North Country late Thursday night and Friday morning, but
this will not amount to much with an eventual change to rain
expected even there.

This system will slowly pull out next weekend, with a few scattered
showers lingering into Saturday as the trough and surface low move
off the east coast, with northwest flow and wrap around moisture
hanging back across the Lower Great Lakes. Moisture and rain chances
should diminish by Sunday as the trough moves well off the eastern
seaboard. The 12Z GFS develops a few showers of rain and wet snow
later Saturday night and Sunday with a weak northern stream trough,
but for now favored the drier ECMWF solution for this time period.

Temperatures will likely run near to slightly above average through
the period, with highs generally in the upper 40s to lower 50s and
lows in the 30s.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
For the 06Z TAFS flight conditions that are generally VFR across the
region will likely lower to IFR across all 5 TAF sites as a moist
airmass remains along with light winds.

A weak frontal boundary will cross the region between 09Z and 15Z,
and along this frontal boundary will be chances for showers, along
with areas of fog. Visibilities will likely lower to IFR or lower
for a 2 to 4 hour period around sunrise, with a then northern flow
maintaining IFR ceilings for a period of time into the afternoon
hours. These IFR CIGS will likely remain longest across the So.
Tier, including the KJHW terminal.

By tonight an area of high pressure will be funneling much drier air
across the region. This will thin the low stratus, that may remain
MVFR (IFR So. Tier) through Tuesday night.

Outlook...

Wednesday and into Thursday...VFR.

Thursday night into Saturday...MVFR/IFR with occasional rain showers.

&&

.MARINE...
A weak to modest pressure gradient across the Lower Lakes
Region will lead to continued relatively light winds and minimal
waves right through Tuesday. A somewhat stronger northerly flow
will then follow Tuesday night through Wednesday as strong
Canadian high pressure builds across the Great Lakes...however
winds and waves are expected to remain below advisory levels.

&&

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

&&

$$

SYNOPSIS...THOMAS
NEAR TERM...JJR
SHORT TERM...ZAFF
LONG TERM...HITCHCOCK
AVIATION...THOMAS
MARINE...JJR



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