Forecast Discussion for BUF NWS Office
003
FXUS61 KBUF 221936
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
236 PM EST Wed Feb 22 2017

.SYNOPSIS...
Unseasonable warmth will continue through Saturday morning along
with a few passing showers.  Locally dense fog will also be a
possibility through Thursday, particularly near Lake Erie and Lake
Ontario. A strong cold front will move through Saturday.  This may
be preceded by some thunderstorms.  Following the front, expect
breezy to windy conditions, along with a return to some lake effect
snow east of the lakes by Sunday.

&&

.NEAR TERM /THROUGH THURSDAY/...
The jet that was responsible for the weekend pummeling over Southern
CA continues to stream eastward and will be responsible for the
development of two surface lows over the next two days.  The first
will be rather weak, and is already approaching the northern Great
Lakes region.  The 2nd low will mark then end of the warm spell when
it moves NE of WNY later Sat AM.  For the near term, we will follow
the first low as it continues east into Southern Ontario by Thursday
morning. The warm SW flow to the S of the low is not directly
tapping the Gulf or Atlantic due to an upper level low over the
Gulf, and therefore deep synoptic moisture is lacking. However,
there is abundant low level moisture. With dewpoints surging into
the low 50s over the 30F degree lakes, expect some advection fog to
develop overnight.  This is not a guarantee, but with the history of
the large scale fog formation upstream earlier together with Lake
Ontario fog this morning, would expect more widespread fog formation
tonight with the added moisture and warmth overhead.  Will issue a
dense fog advisory for the lake plains in anticipation of fog
development late today and/or tonight.  Otherwise, expect
temperatures to be w-a-y above normal, with lows barely dropping to
50F over WNY and into the 40s to the east.

In terms of precipitation...aside from the scattered showers moving
through the Southern Tier this afternoon, expect mostly dry weather
to last through tonight.  There may be some passing showers on
Thursday AM, but rainfall amounts should be negligible due to the
lacking moisture aloft.  Later Thursday afternoon, some semblance of
a lake breeze front may form toward the Southern Tier as the surface
low moves east across Southern Ontario.  The weak boundary together
with a weak trough south of the low may provide enough of a focus
for the development of a weak line of showers, but again, have a low
QPF in place.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SUNDAY NIGHT/...
The weather will be anything but uneventful during this period...as
a deep storm system will cut to our west and mark a change in the
overlying pattern across the country. Our region will initially be
unseasonably mild with near record temperatures...but as we progress
through the weekend...notably colder air in the wake of the passing
cyclone will send the mercury plunging back towards normal levels.
At the peak of this process...there will be the risk for strong to
damaging winds as well. If that were not enough...there will be some
accumulating lake snows in the typical snow belts east of both
lakes. Lets break this down into the day to day details.

A vigorous shortwave...seen in WV imagery coming ashore in northern
California at midday...will cross the Inter-Mountain West tonight
and Thursday. This will lead to significant cyclogenesis over the
central plains. The resulting surface feature will consolidate into
a deep cyclone over northern Missouri Thursday night...while a
strengthening warm front will extend to the east across Lake Erie to
northern Pennsylvania. As the front slowly pushes north Thursday
night...clouds will thicken across our forecast area with rain
spreading across the western counties during the latter portion of
the night. Have raised pops to likely for the bulk of western New
York while introducing chc pops for the North Country.

The surface low will approach Chicago on Friday as the associated
warm front will grudgingly push north to Lake Ontario. There is
still uncertainty as to the speed of this northward push but little
doubt that the bulk of the region will pick up at least a little
rain in the process. Once again...have chosen to raise pops...this
time to categorical for the counties near and east of Lake Ontario.
Since there will be a fair amount of elevated CAPE...the warm front
could also generate some embedded thunderstorms. The big question
for Friday will be the extent of any clearing over the western
counties...and in particular the Southern Tier. Once in the warm
sector where H85 temps will be in the vcnty of 10 to 12c...any
clearing would promote/support near sfc temps that could soar into
the 70s. This would be near record warmth in many areas (BUF 67/1906
ROC 70/1906). It should be stressed though that this kind of warmth
will NOT come during the typical mid afternoon time frame. Our
warmest weather Friday will come very LATE in the day or during the
evening. Again...this will all hinge on the speed of the northward
push of the warm frontal boundary. Stay tuned.

Friday night...the cyclone will deepen a bit while advancing to Lake
Huron. With the aforementioned warm front far to our north...our
forecast area will be firmly well entrenched in the warm sector.
Temperatures across the region will be steady or will slowly fall in
the evening...then will rise during the overnight hours. The max
temps for the day may very well come between nightfall and midnight
for some areas. That being said...there should be little if any pcpn
within the warm sector. Most of the rain will be focused over the
North Country in the evening in the vcnty of the exiting warm
front...and close to Lake Erie towards daybreak ahead of a powerful
cold front.

A strong 50 knot low level jet will move across the western counties
ahead of the approaching cold front late Friday night. While an
inversion will prevent the bulk of these winds from being mixed to
the sfc...there could still be some gusts over 35 mph across the
higher terrain and adjacent downslope areas.

On Saturday...the deep storm system will further intensify to under
985mb as it will track across western Quebec to the east shores of
James Bay. Its associated cold front will plow across our forecast
area during the morning (midday North Country). While a 50 mile wide
band of moderately heavy showers and possible thunderstorms will
accompany the frontal passage...the main concern will be the strong
winds that will follow. Lets be clear though. At this point...the
event is looking less and less impressive from the standpoint of a
`classic` high wind event...but there is still plenty of potential
for advisory criteria winds. In the column favoring strong winds
will be the track and pressure trend of the storm system...but
opposing this will be the lack of significant subsidence with the
residual low level jet immediately behind the front and the delay
time before near sfc winds veer to the southwest. If this scenario
ere to verify...parts of the region would be looking at winds
gusting into the 40s rather than 50+ mph.

The near advisory criteria winds on Saturday will aid with the
strong cold advection that will be underway. H85 temps that should
be in the double digits (celsius) at daybreak are forecast to drop
off to around -5c by evening. This will certainly not be cold enough
to initiate true lake effect...and the mesoscale process will be
further limited by low level ridging immediately behind the front.
While true lake effect will hold off til after dark...some nuisance
lake enhancement will be possible east of both lakes.

As the cold air deepens Saturday night...H85 temps will plunge to at
least -12c. The burgeoning lake induced instability will then result
in some lake snows east of both lakes. Otherwise...it will be brisk
and much colder than recent days with temperatures Saturday night
falling into the 20s.

The accumulating lake snows and general return to more seasonable
conditions will continue on Sunday and Sunday night. The thermal
trough associated with this scenario will move across our forecast
area on Sunday...with H85 temps averaging -12c. This will make
Sunday the coldest day of the forecast package with highs in the mid
30s...right near climatological norms. While lake snows will remain
in place east of both lakes...the late season diurnal effects will
disrupt any solid bands and somewhat limit daytime snow
accumulations.

Warm advection will then begin over the region Sunday night as low
level ridging will push to our east and the upper level pattern will
flatten out. Lake snows will weaken in the process...especially east
of Lake Erie.

&&

.LONG TERM /MONDAY THROUGH TUESDAY/...
Mother Nature will reload the upper level pattern for yet another
significant `cutter` storm during this period. This pattern...more
typical of the second half of March through April...will lead to
renewed warming with anomalous warmth once again possible by mid
week. If early indications form the medium range ensembles are
correct...this next cyclone could carry a notably higher risk for
strong winds. This will certainly deserve to be watched.

As we open this period on Monday...a relatively low amplitude flow
will be found over the Great Lakes region while a weak cold front
will try to pass through our forecast area. Since there is little
supported suggested with this front...will leave mention of pcpn out
of the package. Temps will be near normal with highs of 35 to 40.

On Tuesday...several robust Pacific shortwaves will dig into...and
amplify...a trough over the western states. This will amplify a
downstream ridge over the eastern half of the country...thereby re-
opening a direct flow out of the GOMEX to the Great Lakes. All of
this will take place while another round of cyclogenesis will be
taking place over the central Plains. While our region will be
mainly rainfree on Tuesday...there will be a low chc for some light
rain showers within the warming airmass.

The weather will deteriorate Tuesday night and Wednesday as the the
deepening cyclone will eject out of the Plains and makes its way to
the Great Lakes. This will lead to more rain for the region...which
could be followed by some strong winds Wednesday night.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
The main concern for aviation will be the increasing potential for
IFR visibilities as a surge of warm and moist air spreads across the
region from the SW. Low ceilings will be more common inland. This
scenario will will be most apparent toward the end of the day with
some LIFR fog possible, and could last well beyond 12Z Thursday. The
relatively cold lakes will promote continued formation overnight.

Outlook...

Friday...morning Rain, but otherwise VFR. Saturday...Periods SHRA
with MVFR and local IFR, then windy.
Sunday...VFR but IFR to MVFR in lake effect snow SE of both lakes.
Monday...VFR, possible MVFR...depending on low location.

&&

.MARINE...
A relatively weak pressure gradient with a neutral to warm temp
advective pattern will keep relatively light winds and manageable
waves in place across the Lower Great Lakes through Thursday.  A
weak front will move through Thursday evening.

The next real time of concern will be late Friday night and Saturday
when a powerful cold front will cross the Lower Great Lakes.
Strong...possibly gale force winds...will be found in the
wake of the front Saturday and Saturday night.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Dense Fog Advisory from 7 PM this evening to 9 AM EST Thursday
     for NYZ001>005-010-011.
MARINE...None.

&&

$$

SYNOPSIS...ZAFF
NEAR TERM...ZAFF
SHORT TERM...RSH
LONG TERM...RSH
AVIATION...CHURCH/ZAFF
MARINE...CHURCH/ZAFF

NWS BUF Office Area Forecast Discussion