Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
1016 PM EDT Friday Mar 14 2014
a deep storm system passing to the north of Lake Ontario tonight
will swing the first of two cold fronts across our region. This will
generate some rain and wet snow showers while bringing an end to our
brief warm up. A second cold front will drop across the area
Saturday morning. Much colder air in its wake will plunge our
Mercury to well below normal levels for the second half of the
weekend into the start of next week.
Near term /through Saturday/...
regional radars this evening display light rain showers and
sprinkles now reaching western New York out ahead of a cold front.
This cold front is located across the western end of Lake Erie and
back into the Ohio Valley from a storm system that is to the
northeast of Georgian Bay. A look at this evening 00z/15th Buffalo
sounding displays a wealth of dry air from the surface upward
through 700 hpa. This inverted v-type sounding is supported of
downward motion enhanced by evaporative cooling from falling light
precipitation. A strong low level jet around 60 knots is found across
wny...and some stronger wind gusts upward to 45 miles per hour will occur at
the onset and just prior to the falling rain showers. This low level jet does
weaken some as it pushes eastward overnight...but still expect many
areas within the County Warning Area to see some gusts 30 to 45 miles per hour...and perhaps
even stronger...as what was measure at the kbuf observation site.
Will hold off on any wind advisories as stronger wind gusts will
likely be localized and briefly within advisory levels.
As an upper level shortwave...now nearing Lake Huron on water vapor
imagery...pushes a cold front across the region expect many areas to
see at least some measurable precipitation...though quantitative precipitation forecast will
generally be less than a tenth of an inch tonight. Will raise probability of precipitation
to low categorical across the County Warning Area...with a band of light rain
showers crossing New York state from west to east overnight.
Behind this front will maintain chance probability of precipitation for some rain/snow
across the hills east of Lake Erie tonight...and likely east of Lake
Ontario where orographic effects and the still presence of the upper
level shortwave may generate additional precipitation.
Temperatures will remain mild ahead of this front with many areas in
the 40s to low 50s. Temperatures will fall some with the
precipitation...which will also increase the low level inversion
which will make these stronger wind gusts less likely from mixing
down to the surface. Behind the cold front temperatures will fall
back into the low to middle 30s across the area late tonight.
On Saturday...the area of low pressure will exit across the Saint
Lawrence valley while strong high pressure will drift across the
Canadian prairies. This will produce a deep cyclonic flow over the
lower Great Lakes with a second frontal boundary poised to drop
across the region late in the afternoon or evening. While the first
frontal passage introduced chillier air...it will be the airmass
behind this second front that will conjure up images of Arctic air
from weeks gone by.
In any case...the combination of the cyclonic flow and weak low
level convergence ahead of this second front will produce some rain
and snow showers over the lower elevations...with primarily snow
showers found above 1500 feet...and east of Lake Ontario where an
upslope flow will lead to categorical probability of precipitation and measurable snow
accumulations (inch or two on the tug).
Temperatures over the western counties on Saturday will be some 10
to 15 degrees f lower than those from today (fri)...while 5 to 10
degrees f cooler east of Lake Ontario. Overall...highs will generally
range from 35 to 40.
Short term /Saturday night through Monday night/...
temperatures will run well below normal through the second half of
the weekend and into the start of next week. An Arctic cold front
will slide across the lower Great Lakes Saturday night ushering in a
fresh blast of dry Arctic air with 850mb temperatures lowering from -10c
Saturday afternoon to between -15c and -20c by Sunday morning.
Arctic high pressure centered over far northern Manitoba Friday
afternoon will build south and shift across the Great Lakes behind
the cold front through the short term period. This surface high will
also keep our area largely shielded from a southern stream storm
which 12z models continue to show shifting across the deep south and
off the Carolina coast.
In terms of temperatures and precipitation...any leftover snow
showers from Saturday afternoon will taper off early Saturday
evening behind the front. Temperatures will plummet overnight down
to the lower teens except toward the North County where reading will
reach the single digits. Northwest flow and increasing lake induced
instability behind the front will keep a chance of some lake effect
snow showers limited to south of Lake Ontario Saturday night and
Sunday. Moisture will be limited as increasingly drier air spreads
south so any Shallow Lake bands that may develop will have little
impact. Arctic air in place Sunday will not allow temperatures to break out
of the teens for the majority of the region. Sunday night through
Monday night subsidence from the surface high will prevent any
additional lake effect showers as the high centers just north of Lake
Ontario. The southern stream storm system passing well to our south
will keep most of its impacts also to the south but a blend of
GFS/sref guidance still gives a low end chance of some light snow
towards the southern tier and Finger Lakes. Temperatures Monday will top
out in the low 20s during the day then dip back into the teens
Long term /Tuesday through Friday/...
after a cold start to next week temperatures are looking to rebound
back to a few degrees either side of average through the rest of the
week. Arctic high pressure and rising 500mb heights will keep dry
weather Tuesday and Tuesday night. South to southeasterly winds will
help boost temperatures into the low 30s south of Lake Ontario with upper
30s across the southern tier and upper 20s east of Lake Ontario.
Across the upper Midwest and western lakes a weak clipper system
will be shifting eastward. This may begin to bring increasing clouds
to western and central New York Tuesday night.
The latest model guidance continues to show timing differences in
shifting this clipper across the central Great Lakes and north of
Lake Ontario. The 12z GFS and Gem are about 12 hours faster than the
12z European model (ecmwf). This has implications on both the temperature and
precipitation forecast for midweek. The faster solutions would bring
in showers on Wednesday but the European model (ecmwf) would hold of till overnight
Wednesday. Temperatures on Wednesday would verify warmer on Wednesday if
the European model (ecmwf) solution is more correct holding off the overcast skies
until late Wednesday. A blend of GFS/ECMWF/wpc was used for a
consensus forecast until better alignment is seen in the models.
This yields low 40s on Wednesday and middle 30s Thursday with the best
chances of precipitation Wednesday night.
Behind the clipper a modified Pacific sourced airmass will settle
across the forecast area as broad high pressure shifts east from
the central states. Some lingering moisture and cooler air aloft may
bring some diurnal instability rain/snow showers on Thursday. The
surface high will shift across the southern half of the East Coast
by Friday with drier air and subsidence likely preventing any
precipitation and bringing near average temperatures to close out the
Aviation /02z Saturday through Wednesday/...
at 00z VFR flight conditions were found across the region. A strong
50 to 60 kts low level jet around 2k feet will necessitate low level wind shear into the tafs
for the first 3-6 hours. This jet will also bring some occasional
wind gusts 20 to 25 knots across the airfields ahead of a cold front.
A few light showers will form ahead of a cold front late evening
through the overnight time frame. This will bring occasional MVFR
flight conditions...with some IFR ceilings possible behind the front
within lingering moisture.
Though much of the time will be precipitation free...some scattered
showers will continue tomorrow with precipitation in the form of
either rain or snow. Ceilings will remain largely MVFR or low end VFR
through the day.
Saturday night into Sunday...VFR/MVFR with a chance of snow showers.
Monday and Tuesday...VFR.
Wednesday...VFR/MVFR with a chance of rain or snow showers.
the surface pressure gradient between a deep storm near Georgian Bay and
high pressure along the southeast coast will remain relatively tight
tonight...and this will keep fresh winds over the lower Great Lakes.
While offshore winds will be in place...will keep wind based small
craft advisories in place through tonight for the ice free nearshore
waters of Lake Ontario.
On Saturday...winds will veer to the west in the wake of a cold
front...then will become northwesterly behind a second cold front
Saturday evening. Marginal Small Craft Advisory conditions will
persist on the open nearshore waters.
Winds will then subside Saturday night and Sunday as high pressure
will build southeast from the upper Great Lakes.
there are some ice jams in place on the Buffalo creeks and elsewhere.
Flows are light and ice jams have been stable. We have not received
any reports of significant flooding...however the gauge on Buffalo
Creek at Gardenville remains steady near flood stage. Afternoon
temperatures warmed into the upper 40s to middle 50s across western
New York and the Genesee Valley. This has resulted in snow pack
ablation...but with only 175 to 200 thawing degree hours this is
not likely to result in significant ice break ups.
However...run-off from this snow melt will cause a modest increase
in flows this evening and tonight. With ice jams already in place in
some locations...this may cause water pooled up behind the jam to
rise tonight in response to the higher flows. Any increase will be
temporary...with temperatures forecast to drop into the 30s
overnight. Any rain showers tonight should be too light to have much
of an impact on flows.
Marine...Small Craft Advisory until 3 am EDT Sunday for loz043.
Small Craft Advisory until noon EDT Saturday for loz042.