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Area forecast discussion 
National Weather Service Buffalo New York
1010 am EDT Tuesday Mar 31 2015

Synopsis...
a fast moving clipper low will continue to bring snow showers across
the southern tier today...before high pressure and dry weather
returns tonight through Wednesday. Temperatures will remain below
normal Wednesday...but Thursday could bring temperatures well above
normal. A cold front Thursday night should bring rain and gusty
winds across the area. The potential for unsettled weather remains
through the weekend.

&&

Near term /through tonight/...
the axis of a 500mb shortwave trough lies across Lake Erie late this
morning. This feature along with a weak clipper low passing south of
New York will continue to bring snow showers to the southern tier
into the afternoon. Kbuf radar continues to show the northern edge
of the snow snow showers lies just south of the Buffalo southtowns.
This mornings 12z radiosonde observation showed a layer of dry air at 800mb which is
helping to keep metropolitan Buffalo and points north and east snow-free
with the only sensible impact being cloudy skies.

Concerning the snow across the southern tier...the track of the
clipper low south of the state line will keep p-type as all snow.
Still expecting snow totals to run in the range of 1 to 3
inches...sub-advisory and with the highest amounts right along the
New York/PA line. The snow will have to contend with daytime heating and
late-March solar insolation through the cloud cover...thus
accumulating snow will become more limited to grassy and elevated
surfaces. As snow rates decrease into the afternoon...and eventually
the snow ends from west to east across the southern
tier...temperatures should manage to climb a few degrees above
freezing. Any accumulated snow remaining on paved surfaces should
quickly melt off by middle to late afternoon.

North and east of the southern tier including Buffalo...Rochester
and the north country... locations along and south of the thruway
could see some snow flurries through early afternoon...but should be
of little consequence. Locations north of the thruway should see an
entirely dry day. Without any precipitation to content
with...temperatures will climb into the upper 30s this
afternoon...with the cloud cover likely keeping most locations from
touching 40.

Tonight...dry air will work in from the north across the forecast
area. This will allow for cloud cover to clear out quickly from
north to south across the area. With the north country clearing out
early and light winds in place...radiational cooling should allow
temperatures to drop into low to middle teens overnight.
Elsewhere...some thin lingering cloud cover should help keep
temperatures in the low 20s. A weak shortwave in the northwesterly
flow may bring a few light snow showers back into the western
southern tier late tonight...but these should not last long and will
result in little additional snow accumulations.

&&

Short term /Wednesday through Thursday night/...
Wednesday morning another much weaker clipper will move across Lake
Erie and the upper Ohio Valley. Any light precipitation with this should
remain west of our region...but it will bring some cloud cover to
the area during the morning especially from the Genesee Valley and
western Finger Lakes into western New York. The morning clouds should
quickly diminish for the afternoon as the clipper washes out and
high pressure builds into the Great Lakes region with increasing
drying and subsidence. Despite the increasing sunshine temperatures
will remain below normal...with upper 30s to around 40 across the
lower elevations of western New York and low to middle 30s across the north
country.

High pressure settles overhead Wednesday evening before drifting to
the eastern Seaboard overnight. This will bring mainly clear skies
and light winds initially...which will allow for some early
radiational cooling. Overnight southerly return flow will develop in
the wake of the departing high and force rising temperatures. A warm
frontal segment will move quickly from southwest to northeast across
the area late Wednesday night...reaching the north country by early
Thursday morning. The deepest moisture and strongest isentropic
upglide with the warm front will Cross Lake Ontario and the Eastern
Lake Ontario region...where a few rain and snow showers are possible
late Wednesday night and early Thursday. For the rest of the
area...dry low levels should keep any precipitation from reaching the
ground with just a period of middle level cloud cover.

The warm front will exit the north country early Thursday...leaving
the entire County Warning Area in the warm sector for the day. Deep south-southwest flow within
the warm sector will allow 850mb temperatures to soar to near +10c. The
combination of a much warmer airmass and south-southwest downslope flow will
boost temperatures into the middle 60s on the lake plains of western
New York...with middle to upper 50s across the interior southern tier and
Eastern Lake Ontario region. The last time we saw a high temperature of 60f
or higher was November 30th at Buffalo and Rochester. The south-southwest wind
direction will keep most of the lake cooling on the Canadian side of
the border...except for areas along the Niagara River off Lake Erie
and near Cape Vincent off Lake Ontario where highs will be
considerably cooler.

Most of Thursday will be rain free...but ongoing warm advection and
isentropic upglide combined with the approach of the initial middle
level height falls and DPVA could produce a few widely scattered
showers during the afternoon with a mix of sun and clouds.

A fairly strong cold front will cross the area Thursday night along
with a convectively augmented middle level shortwave and low level jet
maximum. This will produce several hours of showers...reaching western
New York during the middle evening then spreading east to the Eastern Lake
Ontario region by around midnight. Forcing will be fairly strong...
with convergence enhanced by a 60+ knot low level jet. A plume of
deeper moisture will be captured by this system...with precipitable water rising
to around 1.25 inches along the front. The combination of quality
moisture and dynamics will produce rainfall amounts of a quarter to
third of an inch over a few hours. Both the NAM and GFS also show
some lingering marginal instability along the advancing front with
around 100j/kg of elevated cape and showalter index near 0c. While
these instability values are extremely marginal...in the presence of
a strongly forced environment it may be enough for a few isolated to
scattered thunderstorms along the front. Given the strength of the
low level wind field...any convective showers /with or without
thunder/ along the front may produce very gusty winds.

The rain will quickly end from west to east overnight as the cold
front moves east of the area and a strong push of drying moves into
the lower lakes.

&&

Long term /Friday through Monday/...
Friday will start off dry...but later Friday and Friday night most
medium range guidance continues to suggest a secondary frontal wave
will move through the Ohio Valley and into the northeast forced by a
strong middle level shortwave moving along the advancing baroclinic
zone. This will bring increasing chances of precipitation again later
Friday afternoon and especially Friday night. The European model (ecmwf) remains
stronger and farther north with this feature than the GFS...and has
support from the 00z Canadian Gem with a similar track and
intensity. As this system passes by to our south...colder air will
be filtering into the region and allow rain to change to snow Friday
night. If the timing and track are just right there could even be
some accumulation.

This system will quickly move away from the area Saturday morning
with just a few leftover snow showers in cold northwest flow during
the first half of the day. Temperatures will again drop to well
below normal with highs only in the 30s. Another cold front will
cross the area Saturday night with a chance of more snow showers.
This will keep cold air in place for Easter Sunday with highs again
only in the 30s. High pressure and drying aloft should keep Sunday
dry with a decent amount of sunshine.

By Monday both the GFS and ecwmf bring a sharp baroclinic zone
slowly northward across the area...with a chance of some rain and
wet snow. Looking a little farther ahead...behind this slowly moving
boundary another push of much warmer air should arrive for at least
a day or two around the middle of next week.

&&

Aviation /14z Tuesday through Saturday/...
a clipper low continues to bring snow showers across the New York southern tier
south into Pennsylvania today. Conditions at kjhw remain at LIFR
late this morning. Snow will taper off from west to east across the
southern tier this afternoon. Initially IFR ceilings will linger at jhw
with upslope flow in place...but drier air will eventually work in
from the north tonight to break up the low cloud deck.

Elsewhere...kiag/kbuf/kroc/kart will see little to no impact from
the clipper low outside of middle-high level clouds across the area
today...and thus VFR conditions will prevail. Would not rule out
some isolated/scattered snow showers near kbuf from middle morning to
early afternoon...but these should remain south of the terminal.

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

&&

Marine...
expect a period of light to modest northeasterlies and northerlies
today and tonight as a clipper system passes across Ohio into
Pennsylvania... before high pressure and light winds build back
across the Great Lakes on Wednesday. Southwest winds will increase
on Thursday ahead of an approaching cold front bringing choppy
conditions across the open waters with the highest Ontario waves
along the North Shore. Wind gusts over 20 knots may contribute to
shifting ice on Lake Erie and the eastern end of Lake Ontario. As
the cold front sags south over New York Friday into Saturday winds
will veer to northerly with waves increasing along the southern
Ontario Lake Shore.

&&

Buf watches/warnings/advisories...
New York...none.
Marine...none.

&&

$$

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

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