Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 271902
AFDBUF

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

.SYNOPSIS...
Scattered rain showers will taper off through this afternoon as a
weak storm system moves away from our region. Another weak storm
system will pass by to our south on Tuesday with additional rain
showers tapering off Tuesday night. Following this will be a period
of dry weather Wednesday and Thursday. Mild temperatures today will
slowly trend lower through Thursday as cooler air filters in across
the region.

&&

.NEAR TERM /THROUGH TUESDAY/...
A cyclonic spin on visible satellite imagery places an area of low
pressure over the Saint Lawrence River Valley. A weak occluded front
trails across the eastern Great Lakes where radars are showing some
lingering scattered rain showers over the eastern Lake Ontario
Region and western Southern Tier. A very moist airmass is in place
with dewpoints in the 40s under south to southwest winds ahead of
the front with temperatures in the 40s and 50s. This airmass is
interacting with the cool waters of Lake Erie producing widespread
low clouds with patches of dense fog this afternoon afternoon. This
has been especially so near the Lake Erie shore in the Buffalo metro
area where web cams have confirmed the dense fog shifting east of
Lake Erie across the I-190 and Route 5. Fog is expected to linger
through the rest of the afternoon and with no change in airmass
expected have decided to extend the Dense Fog Advisory through 8pm
for the immediate Lake Erie shoreline.

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 during the first half of the week, then eject
ENE across the central Plains to the Ohio Valley by Friday. 00Z
guidance has come into better agreement, with the ECMWF closer to
the `wet` GFS/GGEM guidance. This system is likely to bring
rain to all areas Friday and Friday night as the deep mid level
trough and associated surface low cross the region. The system
will be filling with time, which generally keeps forcing and
moisture transport on the weaker side which will in turn keep
rain amounts relatively modest.

This system will slowly pull out next weekend, with a few scattered
showers lingering into Saturday as the trough and surface low move
to 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.

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

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
Scattered rain showers are tapering off this afternoon across the
region ahead and along a weak frontal boundary. These showers and a
very moist airmass have contributed to areas of MVFR/IFR cigs/vis
with lowest cigs and vis near the Lake Erie shoreline.

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...SMITH
NEAR TERM...SMITH
SHORT TERM...ZAFF
LONG TERM...APFFEL/HITCHCOCK
AVIATION...SMITH
MARINE...SMITH


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