Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
128 am EDT sun Mar 29 2015
high pressure will bring mainly clear skies and cold temperatures
tonight with dry weather lasting into Sunday. Then 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 today/...
tonight high pressure will build across the Ohio Valley with a
surface ridge extending northeastward over the lower lakes. This
will provide mainly clear skies for our region tonight.
The clearing skies...relatively light winds...and a cold/dry airmass
will allow for good radiational cooling conditions overnight. Since
there is a fairly high confidence in this...the forecast hedges with
a blend of the cooler temperature guidance. This should result in
lows in the teens on the lake plains with single digits in the
colder southern tier valleys and east of Lake Ontario.
High pressure will continue to ridge over our region from the Middle
Atlantic States on Sunday. This will bring dry and sunny
conditions...but temperatures will still be on the cool side. Expect
highs in the upper 30s to lower 40s.
Short term /tonight through Tuesday night/...
Sunday night into Monday...a shortwave trough will work across the
area...and the attendant surface low will track just north of Lake
Ontario. 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. For the remainder of Monday
expect little change in the surface temperature or slowly dropping
temperatures as the air aloft cools. With this in mind...any mix
with rain following the front will probably change back over to snow
in the afternoon...but similar to recent rather weakly forced
precipitation events...any accumulation should be negligible during
the afternoon. 03z...09z...and 15z 03/28 sref output for Monday
show nearly all ensemble members supporting snow as well...and
general profile does support rain with nearly all but the lowest
500ft or so above freezing. With a more saturated profile in the
vicinity of the front...there should be just enough dynamic cooling
to keep the lowest layer from warming as the warmer NAM suggests.
Winds will increase substantially 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 westerly 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 50 miles per hour.
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 Pennsylvania. Will have a mix
of rain and snow with this fast moving system as temperatures will range in
the upper 30s...then temperatures will fall back to the 20s or upper teens
as the low passes.
Long term /Wednesday through Saturday/...
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 /06z Sunday through Thursday/...
VFR will prevail for the rest of the overnight and through all of
the daylight hours on Sunday. High pressure over the Ohio Valley and
lower lakes will slowly drift to the East Coast today...and continue
to provide clear skies. High cirrus level cloudiness will begin to
increase later today ahead of the next system.
This evening a sharp middle level trough and occluded front at the
surface will approach the area. A narrow zone of focused ascent
along this feature will produce a period of light snow...entering
western New York around 02z then overspreading the rest of the area
overnight. This will produce areas of IFR visibility...with ceilings initially
staying mainly VFR. Winds will increase this evening as the pressure
gradient tightens...with gusts of over 20 knots in most areas and
over 30 knots northeast of Lake Erie due to funneling down the lake.
Monday through Tuesday...areas of MVFR and spotty IFR in rain/snow
Thursday...VFR/MVFR. A chance of rain showers.
high pressure will build over the lower lakes tonight with
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.