120
FXUS61 KBUF 091908
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
208 PM EST Sat Nov 9 2024

.SYNOPSIS...
Clouds will increase from west to east later tonight and Sunday
morning, with a period of much needed rain passing over the region
Sunday and Sunday evening. Unsettled weather, especially east of the
Lakes, will linger Monday, diminishing in coverage by Tuesday.

&&

.NEAR TERM /THROUGH SUNDAY/...
Broad high pressure over the region will drift east tonight. This
will maintain fair weather across the region tonight, although there
will be a gradual increase in high level clouds from west to east.
Overnight low temperatures generally in the lower to mid 30s, with
some 20s east of Lake Ontario and normally colder areas of western
New York. The coldest readings should occur earlier in the night as
a developing southerly flow and increasing higher cloud cover
will allow temperatures to steady out or rise later tonight.

High pressure will continue shift off to the east Sunday. This will
send in a milder (highs in the mid to upper 50s) and a more
humid airmass (precipitable water values rising to over an inch)
in advance of a deep occluded low. Associated precipitation
shield will work into western New York by mid to late Sunday
morning, then advance eastward through the day with the
greatest areal coverage expected Sunday afternoon. Rainfall
amounts ranging from less than a tenth of an inch east of Lake
Ontario to perhaps as much as a half inch across southwest New
York. A breezy day is expected ahead of the low with south
winds gusting 20 to 30 mph at times, perhaps a bit higher in
favored downslope areas.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
Unsettled weather continues through roughly the first half of this
period as a pair of robust shortwaves impinge upon the eastern Great
Lakes. The first of these troughs will pass north of the region
across the southern Ontario/Quebec border Sunday night, with its
cold front sliding eastward across the forecast area in tandem. Deep
layer saturation and broad upper level jet support will force the
associated widespread rain ahead of the front to move east of the
Genesee valley headed into late Sunday evening, while the system`s
dry slot works back in across WNY. Have cut back PoPs from
continuity/NBM and adjusted the timing based on latest guidance,
though the upstream 500mb trough axis, presence of a 45-50kt LLJ and
residual low-level moisture will likely produce additional shower
activity in the area. This will especially be the case east of Lake
Erie, where 850H temps in the low single digits and localized
terrain enhancement will likely cause more numerous showers, though
still entirely in the form of rain.

Otherwise, due to the southwesterly orientation of the strong LLJ in
the post-frontal CAA regime, could see onshore winds becoming gusty
for a couple of hours late Monday night, mainly downwind of Lake
Erie and then Lake Ontario a few hours later. Guidance has trended
slightly more aggressive with the strength of this jet, so have
bumped up gusts around the Buffalo Metro and across western
Jefferson County to near 40mph...Though given that the airmass
doesn`t look overly cold and that the FROPA is overnight, these
should be somewhat mitigating factors in higher gust potential.

The primary trough will weaken and shift northeast of the region to
eastern Quebec Monday, as the secondary trough and associated cold
front slides southeast across the Upper Great Lakes and towards the
forecast area. Between these two features, expect on and off lake
effect/upslope rain showers to continue east of the lakes, with more
scattered shower activity elsewhere. A subtle southwesterly wind
shift Monday afternoon ahead of the incoming front should focus the
main lake effect area more northeast of the lakes, though still
primarily south of Buffalo and Watertown. The modest pressure
gradient and cooler airmass over the region will maintain the breezy
conditions through much of Monday.

The front will then move southeast across the eastern Great Lakes
late Monday evening into early Monday night, causing shower activity
to blossom across much of the region though especially southeast of
the lakes. The airmass behind this front looks to be much colder
than the one on Sunday night, with guidance now advertising 850H
temps plummeting down to around -6C or -7C by early Tuesday morning.
This is would be cold enough to support a partial changeover to wet
snow in many areas, with a full changeover across the higher
terrain...Though with moisture greatly lacking by this point, would
expect little to no accumulations before drying out.

A few lingering showers possible southeast of the lakes Tuesday,
though with continued drying of the airmass as strong high pressure
builds in across the Great Lakes, expect a clearing trend through
the day with areawide dry weather lasting through Tuesday night. The
main story here will be the much colder temperatures compared to
Sunday night and Monday, which will actually run several degrees
below normal in most areas for a change.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
High pressure will build across the Great Lakes Wednesday,
supporting a period of fair weather. A weak shortwave and cold front
will approach Wednesday night and will slowly move across the area
Thursday. Still some model disagreement on strength and timing of
this, and given the generally weak boundary it only supports chance
PoPs for now. Precipitation would mostly be rain, although some wet
snowflakes can`t be ruled out across the North Country.

The shortwave exits east on Friday, with a more zonal flow aloft
developing. 850mb temps around 0C could support some light lake
effect precipitation east of the lakes at times, but the majority of
Friday will be rain-free. Slightly warmer air aloft will the move in
for Saturday, which will end any lake effect showers.

Overall temperatures will average near to slightly above normal with
daytime highs mainly in the upper 40s to mid 50s during the period.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
For the 18Z TAFS, VFR flight conditions will continue through the
TAF cycle. Surface high pressure over the region this afternoon
will shift east through Sunday. Variable winds under 10 knots
through this evening will become southeasterly tonight behind
the center of the surface high. Cirrus level clouds will
gradually overspread the state from the west tonight, with mid
level clouds pushing into the region Sunday morning. The leading
edge of rain showers making headway into western New York after
15Z Sunday.

Outlook...

Sunday afternoon...MVFR/IFR with rain.
Monday...MVFR with showers likely.
Tuesday...Mainly VFR.
Wednesday...VFR.
Thursday...Restrictions developing with showers likely.

&&

.MARINE...
High pressure drifting east across the region will maintain quiet
marine conditions tonight. Southerly winds will pick up Sunday
behind the departing area of high pressure and ahead of an
approaching frontal system. Speeds may approach 20 knots, but
the greater wave action will be focused into Canadian waters.

Small craft headlines will be needed Sunday night through at least
Monday night as elevated southwesterly winds of 15 to 25 knots
behind the system cold front Sunday night become westerly
Monday, then west-northwesterly by Monday night. Speeds may
near 30 knots for a time on Lake Ontario early Monday night.
There will be the potential for low end gales force gusts,
behind the cold front Sunday night on both Lake Erie and Lake
Ontario, and on Lake Ontario Monday night, particularly the
central and eastern basin.

Northwest winds will slowly diminish and becoming northerly
Tuesday with small craft conditions improving on Lake Erie.
Conditions will also improve slowly on Lake Ontario Tuesday
into Tuesday night, but will likely remain choppy as winds
become northeasterly approaching 15 knots at times.

&&

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

&&

$$

SYNOPSIS...Thomas/TMA
NEAR TERM...TMA
SHORT TERM...PP
LONG TERM...Apffel
AVIATION...TMA
MARINE...TMA