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Area forecast discussion 
National Weather Service Buffalo New York
308 am EST sun Mar 1 2015

Synopsis...
a weak area of low pressure will move from the Ohio Valley early
this morning to New England by tonight and bring widespread light to
moderate snow to the region. The snow will quickly taper off Monday
morning as high pressure builds back into the Great Lakes. A
stronger area of low pressure will move through the central Great
Lakes Tuesday night. This will spread a wintry mix across the region
which will briefly change to rain as temperatures rise above
freezing Tuesday night. Much colder air will then move back into the
area Wednesday through the end of the week.

&&

Near term /through tonight/...
warm air advection ramping up immediately in advance of weak
shortwave energy rapidly pushing northeast into the Ohio
Valley/southern Great Lakes. The resulting uptick in moist
isentropic ascent anchoring the expansion of light snow as expected.
Regional radars showing the northern edge of the region of light
snow expanding across Ohio and northwest Pennsylvania and will
advance into the western southern tier between 09z and 12z. The snow
shield will continue to expand across the remainder of the area
through the day today. Significant wedge of departing low level dry
air will keep snowfall intensity relatively light at first. Once
column saturation occurs intensity levels will pick up with a
favorable temperature regime becoming more supportive of good
dendrites.

Strengthening deep layer frontogenesis will expand across the region
from middle day into this evening within the exit region of an upper
jet streak. This will largely occur south of the New York state
border. However...the southern tier will be close enough to the
enhanced forcing to see higher intensity snows. While much of the
area will see accumulations in the 2 to 4 inch range...enhanced
amounts in the 4 to 6 inches look reasonable along the southern tier
where a Winter Weather Advisory remains in effect.

Moisture and forcing will begin to slowly diminish tonight as drier
air moves in from the west. This will allow the snow shield to
slowly pull to the east.

Despite the snow...temperatures today will not be as cold compared
to recent days...with highs in the middle to upper 20s for most areas.
Temperatures tonight will be in the 20s given the extensive cloud
cover and light snow.

&&

Short term /Monday through Wednesday night/...
snow showers will linger across western and central New York into
Monday as moisture and cold air continue to wrap around the back
side the departing storm system...shifting across the Gulf of Maine
to Newfoundland. Upslope flow across the higher terrain of the
southern tier and east of Lake Ontario will have snow chances
longest as the synoptic forcing from a 500mb trough and attendant
vorticity maximum pass to our east. Quickly thinning moisture should only
lead up to an additional inch of snow across the higher terrain with
a few tenths elsewhere before ending. A tight pressure gradient and
steep low level lapse rate will allow for some wind gusts of 30-40
miles per hour during the day...especially across the Genesee Valley and Finger
Lakes region.

Some light lake enhanced snow showers or flurries could linger into
Monday evening southeast of Lake Ontario before the subsidence
brought on by a surface high passing just south of New York ends
this threat. Otherwise mainly clear and dry conditions expected.
Cold air advection will lower surface temperatures Monday from the
middle 20s into the teens then dropping into the low single digits for
lows Monday night.

Surface high pressure will quickly shift off the East Coast on
Tuesday as another stronger but warmer storm quickly approaches from
the Central Plains. A Colorado low will rapidly deepen while cutting
toward the Great Lakes. Deep southerly flow ahead of this system
will spread a plume of warm moist Gulf sourced air northward across
the Ohio Valley and northeast Tuesday into Tuesday night. Although
precipitation will be starting as a widespread snow even on Tuesday
afternoon...warmer air aloft and at the surface will change a fair
portion of the precipitation over to rain. There may be some
snow/sleet/frzg rain at times during the transition from frozen to
liquid precipitation and some of the higher elevations will have snow or a
mix of rain and snow. Temperatures will rise from the 20s late Tuesday
afternoon to the lower to middle 30s across much of New York west of
the Genesee Valley during the course of the evening and overnight
hours.

Temperatures will be back on a downward slide by Wednesday morning
as a cold front moves through...changing the precipitation back from cold
rain to wet snow from west to east through the day. The temperatures
will fall from the lower to middle 30s early in the morning to the middle
20s by the end of the across western New York...central and northern New York
will have middle to upper 30s for much of the day with temperatures falling to
lower 30s late in the day.

Much colder air arrives Wednesday night with the passage of an
Arctic front and temperatures will fall back to the lower to middle teens with
some single digits across the hills of the southern tier and the
Eastern Lake Ontario region. A band of lake effect snow is expected
to form across Southern Lake Ontario to central New York.

&&

Long term /Thursday through Saturday/...
Arctic high pressure will expand east from the central states to the
southeast Thursday into Friday with an open channel of cold air
continuing to filter across the region. A low chance of snow remains
in the forecast for western and central New York on Thursday as
models show the cold front which passed east and south of New York
on Wednesday could stall along the appalachian range Thursday. A wave
of low pressure with moisture feed from the deep south may try to
work north along the front with a chance that some snow extends into
our forecast area. Otherwise the Arctic high will keep generally dry
conditions. Later Friday into Saturday models are showing a clipper
system tracking east just to the north of the Great Lakes. Have
added a slight chance of snow for now a week out.

The cold air filtering south across the Great Lakes will keep
temperatures some 10-15 degrees below normal for the end of the week
with highs within a few degrees of 20 and overnight lows down into
the single digits Thursday night and teens Friday night. If enough
southerly air can develop ahead of the possibly clipper low next
weekend temperatures Saturday could push back toward normal.

&&

Aviation /08z Sunday through Thursday/...
middle level clouds will increase and lower from southwest to
northeast in advance of the next system. Light snow will begin to
overspread the western southern tier by around 09z or so with visibility
deteriorating to IFR as the snow develops. The light snow will
slowly overspread the rest of the area on Sunday with visibility coming
down to IFR as it does so. The snow will slowly saturate the low
levels with ceilings dropping to MVFR from southwest to northeast on
Sunday...with some IFR developing across higher terrain.

Outlook...
Sunday night...IFR in widespread snow.
Monday...areas of MVFR/IFR with snow showers...then improving to
VFR.
Tuesday...VFR deteriorating to MVFR/IFR late with a wintry mix
developing.
Tuesday night...MVFR/IFR with a wintry mix changing to rain.
Becoming windy.
Wednesday...windy. MVFR with a chance of snow showers.
Thursday...MVFR with a chance of snow showers.

&&

Marine...
a weak wave of low pressure moves from the Ohio Valley to New
England today and tonight. Winds will initially be light with this
system...but then increase late tonight and Monday as low pressure
deepens over the Canadian Maritimes and strong high pressure builds
into the upper Midwest...tightening the pressure gradient over the
Great Lakes. This will bring another round of Small Craft Advisory
conditions to the areas of Lake Ontario that still have open water.

Another round of gusty winds will arrive Tuesday night and Wednesday
as a moderately strong area of low pressure moves through the
central Great Lakes. This will bring another round of higher end
small craft advisories to the open portions of Lake Ontario.

&&

Hydrology...
our region will see the first above freezing temperatures in over
a month around the middle of the week as a moderately strong area
of low pressure cuts through the central Great Lakes...allowing a
brief surge of warm air to enter our region Tuesday night. Expect
a wintry mix initially late Tuesday afternoon and evening as warm
air aloft moves in over stubborn cold air at the surface. A brief
surge of near surface warming just ahead of the cold front will
change all the precipitation over to rain for a brief time Tuesday night
before cold air comes rushing back into the area Wednesday
morning.

Quantitative precipitation forecast potential with this system appears to be in the half to three
quarter of an inch range...but at least a portion of that will
fall in some sort of frozen wintry precipitation. The deep snowpack will
likely absorb a good portion of the precipitation...and help to
reduce runoff. All of the area creeks and rivers have very
extensive ice pack...however it does not appear it will be warm
enough for a long enough period of time to allow the ice to break
up and begin to move.

Given the above expectations...flooding potential appears low for
the midweek period. The only potential issue may be minor flooding
in poor drainage areas...especially where snow is blocking storm
drains.

&&

Buf watches/warnings/advisories...
New York...Winter Weather Advisory until 7 am EST Monday for nyz019>021.
Winter Weather Advisory from 1 PM this afternoon to 7 am EST
Monday for nyz008.
Marine...none.

&&

$$

Synopsis...tma
near term...tma
short term...Smith/wch
long term...Smith
aviation...church/Hitchcock
marine...tma
hydrology...Hitchcock

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