Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
228 am EDT Tuesday Sep 16 2014
an upper level disturbance combined with a weak surface front will
continue rain showers across the region this morning. The rain will
then taper off from west to east through Tuesday morning with
sunshine returning in the afternoon. An area of high pressure will
bring cool and dry conditions into Wednesday before another cold
front brings a slight chance for rain showers Wednesday night.
Near term /through today/...
area radars show a wide swath of rain showers over western and
central New York early this morning ahead of the axis of an upper
level shortwave trough and surface trough approaching the eastern
Great Lakes. Radar estimated rainfall totals range from a quarter
inch or less from Lake Ontario northward to near an inch along the
New York/PA border. Kbuf shows the back edge of the showers is now pushing
east of Lake Erie so expect activity to taper off from west to east
through the morning hours.
By 12z Tuesday the axis of the upper level shortwave will be across
cny...with the cold front similarly near cny as well. Thus showers
will likely be confined mainly for areas east of the Genesee Valley.
There is not a lot of cold air advection behind this cold front as
850 hpa temperatures only drop a few degrees. However even these 850
hpa reading of around +4c over the Warm Lake waters along with winds
veering to west-northwesterly may bring a Few Lake effect sprinkles
or light rain shower across the higher terrain of the southern tier.
Will leave low chance probability of precipitation in through the morning here...with
daytime mixing ending any activity by late morning. East of Lake
Ontario by time any lake effect showers generate behind the cold
front...feel that it will be late enough in the morning that no
organized showers will develop.
Highs today will range through the 60s. The warmest areas in the
region...where highs may reach into the middle 60s will be across
northwestern Niagara Frontier and the Saint Lawrence valley where
additional sunshine will promote the greatest afternoon warming.
Short term /tonight through Thursday night/...
Tuesday night a weak surface high will build over the lower lakes
and Ohio Valley. This will provide at least partial clearing
initially during the evening. Overnight conditions appear marginally
supportive for stratus development with weak northwest upslope flow
just off the surface...a cool airmass allowing for some lake effect
clouds...and a developing subsidence inversion to trap a shallow
layer of moisture. With this in mind...expect clouds to increase
again overnight south of Lake Ontario...while the north country may
remain more clear. Even with the expected increase in cloud cover
there may be some southern tier valley fog. Assuming the cloud cover
materializes...it will help keep temperatures up a little in an otherwise
chilly airmass. Expect lows in the middle to upper 40s on the lake
plains and upper 30s to lower 40s in the cooler southern tier
valleys and Tug Hill region. If skies do remain clear much of the
night...some of these locations may see patchy frost.
On Wednesday weak high pressure will remain in place. Meanwhile a
middle level trough and weak surface front will move towards the Saint
Lawrence valley later in the day with some increase in clouds during
the afternoon across the north country. South of Lake Ontario any
morning stratus should mix out and give way to increasing sunshine
through the day. 850mb temperatures of +4c to +6 will support highs in the
middle to upper 60s on the lake plains...and low to middle 60s across
Wednesday night and Thursday a weak cold front will sag south across
the region as a middle level trough moves east across Quebec. The front
will be moisture starved and any large scale synoptic ascent will
remain well north and east of the area. The front may produce a few
showers across the Saint Lawrence valley Wednesday evening...but
otherwise expect just a chance of a few sprinkles as it moves slowly
south across the region Wednesday night and Thursday morning.
Northerly upslope flow and some limited lake response may keep these
sprinkles...or perhaps some drizzle going through Thursday morning
from south of Lake Ontario into the southern tier and Finger Lakes.
Another period of northerly upslope flow...lake effect clouds...and
moisture trapped beneath a subsidence inversion will likely produce
more stratus late Wednesday night through a good portion of Thursday
for the bulk of the area.
Steady cold advection and Post-frontal cloud cover will keep
temperatures well below average on Thursday...with highs only in the
upper 50s in most areas.
Thursday night high pressure will build into the lower lakes and New
England. Some stratus may still linger south of Lake Ontario during
the evening...but low level flow will become light later at night
and should allow upslope flow to break down and yield clearing
skies. A cool/dry airmass and light winds will promote good
radiational cooling. Expect lows to drop to around 40 on the lake
plains with middle 30s possible in the cooler spots of the interior
southern tier and Eastern Lake Ontario region with some frost
possible. The Tug Hill and western foothills of the Adirondacks may
drop into the upper 20s to lower 30s.
Long term /Friday through Monday/...
Friday high pressure will drift east across New England and continue
to provide fair weather across our region. Burgeoning southerly
return flow will aid in allowing temperatures to recover after a
chilly morning. Expect highs to reach into the middle 60s on the lake
plains...with lower 60s across the higher terrain and east of Lake
Over the weekend a progressive trough will move across the northern
plains and force downstream height rises and warm advection across
the Ohio Valley and northeast. Surface high pressure will remain
anchored just off the East Coast...allowing for a good push of
southerly flow through the weekend. This will boost temperatures at
least into the middle 70s both Saturday and Sunday across lower
elevations aided by south-southwest downslope flow. The latest 12z GFS remains
consistent with previous runs in keeping Saturday dry...and the new
12z European model (ecmwf) has trended strongly in that direction and now keeps a
frontal zone well to our northwest across the central and western
lakes. With this in mind have removed the probability of precipitation for Saturday. By
Sunday a middle level trough and surface cold front will cross the
region with a chance of showers.
Another trough will dig into the Great Lakes early next week...with
much cooler temperatures again for Monday following the Sunday cold
Aviation /07z Tuesday through Saturday/...
a surface and upper level trough are approaching the eastern Great
Lakes this morning with a swath of rain showers across New York
state. Light to occasionally moderate rainfall and lowering ceilings are
possible across the County Warning Area mainly through 12z. Much of the time should
be VFR...though occasional MVFR visibilities and IFR ceilings are possible
within the rain showers.
The axis of the upper level trough will pass east across New York this
morning bringing an end to the rainfall. Some scattered light showers
or sprinkles may linger across the southern tier along with MVFR
ceilings through the morning as boundary layer winds veer around to
northwesterly. Otherwise decreasing clouds are expected after 12z
with a general light wind flow as high pressure builds overhead.
Some lake effect clouds are possible in the upslope flow inland from
the lakes tonight but expect this to remain VFR.
Tuesday night through Saturday...generally VFR. Some patches of MVFR
ceilings both Tuesday and Wednesday night. Some valley fog with
localized IFR flight visibilities across the southern tier each morning.
northwesterly winds will develop behind the passage of a weak cold
front and upper level shortwave today. These winds will bring 2 to 4
foot waves on Lake Erie...and on Lake Ontario a longer fetch to the
lake will allow for 3 to 5 foot waves. Based on this along with
winds nearing 20 knots will continue small craft advisories for Lake
Ontario this afternoon through this evening.
Winds will eventually back around to the west tonight as high
pressure begins to build into the lower Great Lakes. Winds and waves
will gradually subside through the overnight hours and into
Wednesday before building once again Wednesday night as a cold front
drops south out of Canada.
Marine...Small Craft Advisory from 2 PM this afternoon to 5 am EDT
Wednesday for loz043>045.
Small Craft Advisory from 2 PM this afternoon to 11 PM EDT
this evening for loz042.