Area Forecast Discussion
Issued by NWS Buffalo, NY

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956
FXUS61 KBUF 272104
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
504 PM EDT Mon Mar 27 2017

.SYNOPSIS...
An elongated region of low pressure extending from Southern Ontario
to the Lower Ohio Valley will push eastward to the East Coast through
Tuesday. This system will bring some additional rain showers to the
area through Tuesday...before strong high pressure builds across the
region and brings a return to drier and cooler weather for Tuesday
night through most of Thursday. Another low pressure system passing
by to our south will then bring a return to more unsettled conditions
for the end of the week.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 5 pm...regional radars show that widely scattered light showers
across the Southern Tier and North Country continue to diminish...
with these still expected to mostly dissipate by sunset. Meanwhile
regional satellite imagery shows an area of drying continuing to push
into the area from the south and west...with breaks in the cloud cover
now developing into far western New York. While regional obs and area
webcams show that this is generally leading to improving visibilities
and ceilings across much of the Buffalo area as of this writing...areas
of dense fog still persist along the immediate Lake Erie shoreline
and portions of downtown Buffalo...thanks to the continued southwesterly
flow of very moist air off the cool waters of Lake Erie. Given the
latter and also that it`s now the evening rush hour...have left up the
dense fog advisory for Northern Erie county for the time being.

A narrow area of surface high pressure will briefly shift across New
York this evening. Light winds and subsidence associated with this
low will trap low level moisture and allow for more fog to develop
overnight. At this point, have fog in the weather grids but have not
gone as low as dense fog outside of the small area near the northern
tip of Lake Erie. Another area where dense fog may form is across
the Eastern Lake Ontario region where heavier showers fell earlier
today.

After midnight, a slowly filling area of low pressure will advance
across the Ohio Valley. Warm air advection, with another surge of
low level moisture and weak synoptic lift will promote another round
of rain showers shifting into western NY. Highest POPs are in the
western Southern Tier closer to the surface low. Temps will not fall
much tonight with low clouds. Low expected to only slip back into
the low to mid 40s.

The surface low will track well to our south Tuesday across West
Virginia and Maryland. This low should produce a few hours of rain
especially toward the NY/PA border but have left likely-range POPs
up to the southern Lake Ontario shoreline during the morning hours.
The eastern Lake Ontario region is forecasted with chance-range POPs
as the swath of low level moisture will be spread across all of NY
although forcing that far north may be due to a shallow shortwave
trough glancing the US/Canada border. Otherwise, look for some
clearing of skies late in the day across WNY as arctic high pressure
begins to nose south across the eastern Great Lakes in the wake of
the shortwave. Highs will range from the low 50s across Western New
York to the upper 40s across the Eastern Lake Ontario Region.

&&

.SHORT TERM /TUESDAY NIGHT 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 /21Z MONDAY THROUGH SATURDAY/...
As of 21z...regional radars show that widely scattered light showers
across the Southern Tier and North Country continue to diminish...
with these still expected to mostly dissipate by sunset. Meanwhile
regional satellite imagery shows an area of drying continuing to push
into the area from the south and west...with breaks in the cloud cover
now developing into far western New York. While this is leading to at
least some improvement in flight conditions in this particular region...
local LIFR still persists across portions of the Buffalo area owing to
a continued southwesterly flow of very moist air off the cool waters
of Lake Erie.

Winds will diminish to light and variable overnight as weak high
pressure quickly shifts across the region. The weak flow and
lingering low level moisture trapped beneath this low should still
allow for low stratus in the IFR/MVFR range and areas of fog across
the region. After midnight another round of rain showers will begin
shifting across WNY with best timing for showers being 12z-18z. IFR
vis and cigs will accompany the second round of showers which looks
to begin to improve back to MVFR toward Tuesday afternoon.

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

&&

.MARINE...
A weak area of low pressure will exit across the Saint Lawrence
River Valley this afternoon. Another weak low will pass well to our
south Tuesday with some showers possible across the lakes but
otherwise winds/waves should remain fair through at least
Thursday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Dense Fog Advisory until 8 PM EDT this evening for NYZ010.
MARINE...None.

&&

$$

SYNOPSIS...JJR
NEAR TERM...JJR/SMITH
SHORT TERM...ZAFF
LONG TERM...HITCHCOCK
AVIATION...JJR/SMITH
MARINE...SMITH



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