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Area forecast discussion 
National Weather Service Buffalo New York
346 PM EDT Monday Mar 30 2015

Synopsis...
rain and wet snow showers will quickly taper off early this evening
as weak high pressure briefly builds across the area. A fast moving
clipper low will then bring a period of light snow to the western
southern tier on Tuesday...before high pressure and dry weather
returns areawide Tuesday night and Wednesday. Temperatures will
remain below normal through Wednesday...before a brief surge of
much warmer air arrives on Thursday.

&&

Near term /through Tuesday/...
as of middle afternoon...another significant shortwave and its
attendant region of deeper lift and wraparound moisture is fueling a
second round of scattered to numerous rain and wet snow showers
across the region...with the most numerous activity presently found
across far western New York. This activity will continue to
spread/develop southeastward across the remainder of the region
through the late afternoon hours...before rapidly diminishing from
northwest to southeast this evening as modest surface-based ridging
and large-scale drying/subsidence quickly builds in behind the
departing shortwave. This should result in a return to fair and
mainly dry weather by the middle evening hours south of Lake
Ontario...and around/shortly after midnight east of Lake Ontario.
Given marginal boundary layer temperatures...any additional accums out of
these should be on the order of an inch or less and mainly confined
to the higher terrain...with the greatest amounts found across the
Tug Hill and Adirondack foothills east of Lake Ontario.

After that...expect dry and fair weather to largely prevail for the
balance of tonight...before a fast-moving clipper system dives
across the upper Ohio Valley very late tonight and Tuesday. Compared
to earlier packages...the 12z guidance suite has universally
shifted a bit further south with the track of this feature...and as
a result now keeps its narrow region of most impressive lift/
moisture...and consequently its greatest overall quantitative precipitation forecast confined to
north central Pennsylvania. As a result...the potential for
advisory-worthy snows out of this has decreased across the higher
terrain south of the New York thruway...with a period of generally
lighter snow now appearing to be a more likely outcome...with any
accumulating snow mainly confined to the western southern tier at
that. With the above in mind...have elected to press the steadier
snows associated with this system southward from our previous
continuity...with the bulk of any snow and resultant accumulations
now mostly confined to the western southern tier...where an inch or
two could accumulate near the state line. Elsewhere...have
maintained a chance of snow to about as far north as the thruway
corridor...with dry/fair weather otherwise expected to prevail
further north.

As for temperatures...lows tonight should generally range from the lower to
middle 20s across the north country to the upper 20s elsewhere. On
Tuesday...expect another day of below average readings with highs
once again remaining confined to the middle and upper 30s in most
places.

&&

Short term /Tuesday night through Thursday/...
surface high pressure will build across the region Tuesday night and
Wednesday...which will bring dry weather and a fair amount of clear
skies. The upper level trough axis will be across New England which will
maintain a cool northerly flow with below normal temperatures. Lows
Tuesday night should range from the lower to middle 20s south of Lake
Ontario to the teens across the Eastern Lake Ontario region where
the snow pack is still in place. Highs Wednesday should run about 10
degrees below normal...ranging from the middle 30s to lower 40s.

A warm front will lift toward the region Wednesday night...which
will be preceded by middle-level warm air advection. This will lift an
area of clouds across the region...and may spark a stray rain or
snow shower across the north country. Lows should come Wednesday
evening...with an increasing southerly flow causing temperatures to
rise late Wednesday night.

Warm air advection will continue Thursday as the surface warm front
lifts northward across our region. This will bring some of the
warmest air western New York has seen in quite some time. Guidance
is good agreement with 850mb temperatures rising to 8 to 10c...and
downsloping from the south-southwest flow should warm things even more in the
lower Genesee Valley and Finger Lakes regions with highs likely to
top 60f. The front may not fully clear the Eastern Lake Ontario
region and a modest lake breeze may develop across Eastern Lake
Ontario. Flow across Lake Erie may also keep Niagara Falls a bit
cooler. 12z NAM/GFS/ggem/ECMWF do bring in measurable quantitative precipitation forecast Thursday
afternoon...but with western New York in the warm sector this is
convective precipitation which will probably be more hit or miss
showers despite model agreement for quantitative precipitation forecast. A cold frontal passage will
eventually bring steady rain showers...but consensus suggests this will
probably hold off until after sunset Thursday.

&&

Long term /Thursday night through Monday/...
a cold front will drop across the region Thursday night...with 12z
GFS/ggem/ECMWF in good agreement. A west-southwest upper level flow should
provide good access to moisture and this combined with model
agreement gave US confidence to raise probability of precipitation to categorical.

After this...forecast confidence diminishes significantly. The 12z
GFS pushes the frontal boundary fully to our south...while the European model (ecmwf)
stalls the front across our region and the ggem between the two
solutions. Regardless of frontal position...all guidance lifts a
wave along this stalled boundary on Friday. Given its position of the
front the European model (ecmwf) a much wetter solution...with Friday and Friday
night the most uncertain forecast period. Regardless of frontal
position...the passage of the wave of low pressure will bring
colder air back into the region for Saturday. This will change
lingering showers over to snow late Friday night and into Saturday
with temperatures aloft possibly even cold enough for some lake
effect clouds or weak lake effect snow showers. Highs on Saturday
will probably only be in the 30s in most locations.

After this a fairly strong frontal boundary is forecast to develop
near our region. Although model guidance is in good agreement on
this...it still is a difficult temperature forecast. There is a
little better chance that we will be on the warm side of the front
on Monday than Sunday...with a low chance of probability of precipitation near the stalled
front.

&&

Aviation /20z Monday through Saturday/...
a second shortwave and attendant round of deeper lift and wraparound
moisture will cross the region this afternoon...and will bring a
second round of rain and wet snow showers along with areas of MVFR
vsbys/cigs. Some brief IFR visibilities and ceilings will also be possible
across the higher terrain...though these should remain more
localized. Moderately strong winds will also continue through late
afternoon...with gusts to around 30 knots commonplace in many areas.

The rain and wet snow showers will then quickly taper off from
northwest to southeast this evening. This should allow conditions to
improve back to VFR by early this evening at the lower elevations...
though MVFR ceilings will probably linger longer across the higher
terrain...with this especially the case east of Lake Ontario.

On Tuesday...a fast-moving clipper system will dive southeastward
across the upper Ohio Valley. This feature should bring a period of
light snow and attendant IFR conditions to the western southern
tier...while further north conditions should remain predominantly
VFR.

Outlook...
Tuesday night and Wednesday...VFR.
Thursday and Thursday night...VFR/MVFR with rain showers becoming
likely.
Friday...VFR/MVFR with a chance of rain showers.
Saturday...VFR/MVFR with a chance of snow showers.

&&

Marine...
brisk westerlies across the lower Great Lakes will diminish tonight
as weak high pressure builds across the region. A period of light to
modest northeasterlies and northerlies will then follow Tuesday and
Tuesday night as a clipper system passes across the Ohio Valley...
before high pressure builds back across the Great Lakes on
Wednesday.

&&

Buf watches/warnings/advisories...
New York...none.
Marine...Small Craft Advisory until 5 am EDT Tuesday for loz043.
Small Craft Advisory until 11 PM EDT this evening for
loz042.

&&

$$

Synopsis...jjr
near term...jjr
short term...apffel
long term...apffel
aviation...jjr
marine...jjr

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