Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
448 am EDT Sat Mar 28 2015
lake effect snow showers south of Lake Ontario this morning will
slowly end today as drier air begins to build into the region.
Temperatures will be way off the mark at more than 20 degrees below
normal for late March. High pressure will bring mainly clear skies
and cold temperatures tonight with dry weather lasting into Sunday.
Low pressure passing to our north will bring a few rain and wet snow
showers to the area Sunday night and Monday. Temperatures will
slowly moderate early next week before a stronger push of warm air
arrives for the second half of the week.
Near term /through tonight/...
the evolution of lake effect snow off Lake Ontario has been
fascinating overnight with a well defined mesoscale-low moving south off
the lake and passing between Buffalo and Rochester. This feature has
enhanced convergence from Rochester west across the Niagara Frontier
and concentrated snow showers into a few areas of locally heavy
snow. Fortunately the feature has remained progressive...which has
likely limited accumulations to around 2 inches or so. The mesoscale-low
will continue to drift south and fall apart through early morning...
which will allow more traditional narrow multiple bands to develop
on the northerly flow in its wake.
Cold northerly flow will continue to support lake effect snow
showers south of Lake Ontario through this morning. 850mb temperatures
bottoming out around -18c will support lake induced equilibrium
levels of around 7k feet through the morning before drying and
subsidence force the inversion to lower during the afternoon. In
addition...strong diurnal mixing from the higher late March sun
angle will also tend to break up any remaining bands of lake effect
snow showers into open cellular convection over the land by early
With this in mind...expect the organized snow showers south of the
lake to produce another inch or so of accumulation in spots through
late morning. Most of this will be confined from the Genesee Valley
westward given the due north flow and remaining ice cover at the
east end of the lake. The snow showers will also extend into the
higher terrain of the western southern tier and Bristol hills with
some enhancement from upslope flow. By the afternoon any remaining
snow showers will slowly diminish to flurries and end...with the
high sun angle preventing any further accumulation. Clouds will hold
on through much of the day in most areas with the northerly upslope
flow and cold air aloft supporting plenty of strato-cu. The best
chance of some sunshine during the afternoon will be near the lakes
as strong mixing attempts to flip the lake process from cloud
generator to more stable lake shadows.
High temperatures will be way off the mark today...with middle 20s on
the lake plains and upper teens on the hills. This is more than 20f
below normal. North winds at 12-15 knots will produce single digit
wind chills at times making it feel like mid-winter.
Tonight high pressure will build across the Ohio Valley with a
surface ridge extending northeast into the lower lakes. This will
provide mainly clear skies outside of some limited lake effect
clouds southeast of Lake Ontario. The clearing skies...relatively
light winds...and a cold/dry airmass will allow for good radiational
cooling conditions overnight. Expect lows well down into the teens
on the lake plains with single digits in the colder southern tier
valleys and east of Lake Ontario.
Short term /Sunday through Monday night/...
Sunday...shortwave ridging overhead will push a surface high from
the Ohio Valley to the Middle Atlantic States. Winds will veer to the
south...bringing increasing warm air advection ahead of the next
approaching shortwave trough. This will allow temperatures to
recover after the cold day on Saturday...with late-day high
temperatures pushing into the upper 30s. The southerly winds will
also bring some downslope warming along the Genesee Valley and the
northern Finger Lakes region...with some low 40 degree readings not
out of the question.
Sunday night into Monday...a shortwave trough will work across the
area...and the attendant surface low will track just north of the
forecast area. By Sunday night...increasing qg forcing ahead of the
vorticity maximum will spread a mixture of rain and snow showers across the
area. The surface cold front will cross the area early Monday
morning...and will act to help to better organize the precipitation.
This may be the best time frame for any light snow
accumulations...before sunrise Monday...however surface temperatures
are still expected to be fairly marginal. Precipitation will become
more scattered/showery behind the cold front on Monday...and should
become primarily rain as daytime heating works to modify a very
marginal airmass. Winds will also increase along and behind the cold
front passage from Sunday night through the day Monday. The
favorable surface low track to the north of the forecast area will
support a core of 40 to 50 knot southwest winds at 925 mb. Low-level
lift and weak cold air advection behind the cold front will help to
limit the full mixing potential of these strong wind aloft...but
will likely still result in winds 20 to 30 miles per hour with gusts as high as
40 miles per hour. The strongest winds will mainly be along the lakes and Lake
Shores / the Niagara Frontier due to winds funneling up Lake Erie /
and into the lower Saint Lawrence River valley off Lake Ontario.
By Monday night...winds will weaken as the surface low pulls out and
precipitation chances will diminish as drier air works in from west
to east across the forecast area. Given the lack of a significant
cold air connection behind the surface low...low temperatures Monday
night into Tuesday morning will mainly be in the upper 20s.
By Tuesday...models are in good agreement about a clipper shortwave
diving from the upper Great Lakes into PA. However...there is still
disagreement on the exact north/south placement of the wave as it
moves quickly off the East Coast by Tuesday night. The ec solution
continues to be a little sharper with the wave... which enhances the
forcing and also pulls in slightly cooler temperatures across New
York state than the GFS suggests. Highest confidence in seeing
precipitation on Tuesday is across the southern tier...with chances
diminishing toward the north country...which may see little to no
impact. Also given the uncertainty in how much cold air the system
can tap into...ptype remains in question. Even if it were cold
enough for all snow...surface temperatures and solar insolation may
be enough to mitigate accumulations. The system quickly exits
Tuesday night with clearing conditions and low temperatures back in
the middle to upper 20s.
Long term /Tuesday through Friday/...
Wednesday into Thursday...models are in good agreement for some
low-amplitude ridging working across the area. This will bring
temperatures warming into middle 40s on Wednesday / which looks like
the only certain dry day in the extended forecast. As the ridge axis
work across the area on Thursday and southwesterly flow becomes
established aloft...temperatures could push well into 50s. The trade
off for these warmer temperatures will be increasing cloud cover and
chances for precipitation to close out the week.
Models are in good agreement about the weather pattern becoming more
unsettled by late Thursday through Saturday as overall troughing
looks looks to be a sure bet. However models continue to struggle
with the exact details. Following the last several runs of both the
GFS and European model (ecmwf)...the solutions have bounced around on showing a
strong low developing in the Friday to Saturday time frame.
However...the tracks of the surface low have ranged from just west
of the forecast area to a coastal low track / and some of the
operational GFS runs losing the system at times. The ec and several
of the GFS/ec ensemble members continue to be fairly consistent in
developing this stronger system...with the last several runs showing
a trend toward a more westerly track. Will have to keep an eye on
this time frame for a more active weather period.
Aviation /09z Saturday through Wednesday/...
lake effect snow showers will continue to produce areas of IFR south
of Lake Ontario through this morning. The most concentrated area of
snow will fall over the next few hours across the Niagara Frontier
including near kbuf-kiag as a stronger area of convergence persists
near what was once a meso-low. Ceilings will generally be MVFR within
the lake effect snow showers...with IFR in the heaviest activity.
East of Lake Ontario expect much better conditions with nothing more
than some VFR ceilings and a few flurries.
The snow showers will gradually diminish from middle morning through
early afternoon with visibility improving to MVFR and then VFR. Ceilings will
also improve from MVFR in the morning to mainly VFR by afternoon
with daytime mixing. Tonight a ridge of high pressure will build
into the region with VFR conditions under mainly clear skies...
except for some lake effect clouds and local MVFR ceilings southeast of
Lake Ontario mainly east of kroc.
Monday and Tuesday...areas of MVFR in rain/snow showers.
moderate northerlies will continue to produce marginal Small Craft
Advisory conditions on the open portions of Lake Ontario today. High
pressure will build into the lower lakes tonight with winds
subsiding to below Small Craft Advisory levels.
A moderately strong area of low pressure will pass just north of the
lakes Sunday night and Monday. This will bring a period of stronger
southwest winds and high end Small Craft Advisory conditions to the
open portions of Lake Ontario. It appears sustained winds should
peak out around 30 knots...although a brief period of low end gales
is not out of the question Monday afternoon.
Marine...Small Craft Advisory until 2 PM EDT this afternoon for loz030-