Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 250940
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
440 AM EST Sun Feb 25 2018

.SYNOPSIS...
Strengthening low pressure will move from Lake Superior today to
Hudson Bay tonight. Widespread rain will end late this morning,
giving way to strong to damaging winds, particularly northeast of
Lake Erie. A dry and mild period of weather is expected early next
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A deepening low pressure system near Lake Superior will continue to
track northeast toward Hudson Bay through tonight. The accompanying
upper-level PV max will track northeast from near Chicago across
Michigan into southern Ontario later today. Impressive moisture
advection with a stout low-level jet of 60-70 knots ahead of the low
pressure system has resulted in a mature baroclinic leaf in WV
imagery across the eastern Great Lakes this morning. Radar imagery
shows widespread soaking rainfall across the region.

The only exception to this mainly rain event is the North Country
early this morning. Mesonet observations continue to show some
localized sub-freezing temperatures near the Tug Hill and along the
Saint Lawrence valley where the northeast flow is slow to scour out
as expected. Thus the winter weather advisory for Jefferson and
Lewis continues this morning with up to a tenth of an inch of
freezing rain possible. However, this will likely only last through
mid-morning at best, as warm advection will win out, with surface
temperatures expected to rise above freezing.

Also, with the strengthening low-level jet, some gusts of 45-50 mph
are possible off the Chautauqua ridge early this morning with
downsloping developing there, as well as funneling up the Black
River Valley later this morning. A wind advisory is in effect for
Jefferson and Lewis today for this effect, and the high wind warning
starts early in Chautauqua county to cover this downslope effect.

As the main push of moisture advection and forcing with the low-
level jet departs to our northeast this morning, the break in
precipitation across Ohio will move across western NY. This will
allow for a brief warm up into the low to mid 50s across western NY
and the Finger Lakes. Then the sharp cold front boundary, currently
visible on regional radar imagery in western OH, will then blast
across the region. Expect a fine line of moderate to heavy rain to
accompany this frontal passage, along with a chance of thunder.

Immediately behind the cold front passage, expect to see winds shift
to the southwest and quickly increase, marking the onset of our high
wind event across western NY. BUFKit profiles suggest a narrow hour
window of strong post-frontal subsidence with about 55 knots
available to mix to the surface. If this works out as expected, the
sudden onset of these high winds behind the front could result in
the majority of any wind damage and downed trees across the warned
area northeast of Lake Erie. Wind gusts behind this front will
likely max out just over 60 mph in the favored corridor between
Buffalo and Rochester, near Batavia. Interestingly, as is
historically observed, forecast profiles suggest an hour to two lull
in the high winds is possible. However, once the cold advection acts
to further steepen the low-level lapse rates and the synoptic
subsidence associated with the PV max track by to our northwest
arrives across western NY, expect to see clearing skies and increase
in winds back to or close to high wind criteria. By this point,
winds aloft available for mixing down will be around 50 knots. Thus
expect more regular gusts of 50, up to 60 mph, will be observed
across the Niagara Frontier over to Rochester. High wind headlines
remain unchanged, focusing northeast of Lake Erie, however have
expanded a Wind Advisory for gusts to around 50 mph to include
Cattaraugus, Allegany, Livingston, Ontario and Wayne Counties.

If you`re looking for the bright side today, other than the wind,
and the temperatures falling from the 50s late this morning, to
around the 40 degree mark by later this afternoon, you will at least
see some sunshine for a time this afternoon.

By sunset this evening, the stronger winds aloft will depart to our
east, and we will begin to decouple with the loss of daytime
heating. This should quickly shut down the wind event this evening.
Continued cold advection overnight will maintain a westerly breeze
across the region, with temperatures falling to around the freezing
mark overnight tonight.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
The new work week will start out with fair and dry weather courtesy
of surface high pressure and mid-level ridging that is forecast to
slide east from the Midwest to Mid-Atlantic states Monday through
Tuesday night. The ridging and persistent southwest flow will
support temperatures remaining well above normal for late February.
Highs Monday are expected in the low to mid 40s and Tuesday climbing
into the upper 40s to low 50s. Overnight low temps Monday are
expected to dip into the mid 20s to low 30s but running a little
milder Tuesday night under southerly flow mainly bottoming out in
the low to mid 30s.

Wednesday into Wednesday night models show a weak surface low
crossing the eastern Great Lakes and subtle shortwave rounding the
mid-level ridge. A trailing cold front is forecast to drop south or
dissipate over western and central NY. This will mainly be marked by
an increase in cloud cover from north to south as synoptic scale
forcing is very weak but there will be a slight/low chances of rain
showers or possibly some wet snow over the Saint Lawrence River
Valley. High and Low temps will run a degree or two higher than
Tuesdays readings which will be about 15 degrees higher than normal.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
While temperatures will continue to average above normal for the
second half of the week into next weekend, there will be a distinct
day to day cooling trend. Along with the higher than normal
temperatures...there is high confidence that it will be quite
unsettled from later Thursday into Friday.

The main culprit for the inclement weather will be a newly formed
closed low that is forecast to track from the Midwest to the Mid-
Atlantic Thursday into Friday. While guidance has come into better
agreement with the existence and general track of this
feature...there are still uncertainties as to how far the system
will move off the coast by the weekend.

Thursday...an occluding surface low will be in the process of
drifting east across Illinois and Indiana. As the system moves
east...the occluded front looks to become established near and just
southwest New York. An anomalously strong southeasterly low level
jet in advance of the storm system will advect abundant (PWAT values
0.75 to 1") Atlantic based moisture up and over the occluded frontal
boundary. This will result in widespread rain over our region
midday/afternoon Thursday into Thursday night. WPC Day4/5 QPF
guidance shows 0.75 to one inch of rain during this process. If
additional rainfall occurs, hydro issues will be a concern. There
could be an occasional mix of wet snow across the North Country as
some colder air will try to advect into the region from New England.

The large storm system will pass by to our south late Thursday night
and Friday. Atlantic moisture will continue to be transported back
to the west by the anomalously strong and persistent easterly flow.
Upslope and residual frontogentic forcing will be the main source to
generate the precipitation...which will be weaker in intensity.
Colder air being wrapped into this system will allow some of the
rain to mix with or change to wet snow...but with max temps in the
vcnty of 40f...do not anticipated appreciable snow accumulations.

Confidence in the forecast will drop off considerably later Friday
night and Saturday...as the exiting speed of the closed storm system
will come into play. While scattered mixed showers can be expected
Friday night just low chc pops linger on Saturday.

&&

.AVIATION /10Z SUNDAY THROUGH THURSDAY/...
A very strong low-level jet will move across the region and cause
LLWS this morning. SW surface winds will increase however a strong
inversion will keep the strongest gusts aloft until a cold front
comes through Sunday midday. Southerly winds will increase to 55kt
at 2k feet by Sunday morning.

Widespread rain continues across the region early this morning,
however cigs/vsbys are expected to stay VFR to MVFR. Brief periods
of IFR can not be ruled out but confidence is low to add to TAF. A
brief break in rain is possible this morning, however a line of
showers with possible TS will then cross the forecast area from west
to east between 12-17Z, marking a cold front passage.

Behind the strong cold front passage, very strong winds are expected
to mix down to the surface immediately behind the front producing
southwest winds 15-25kts with gusts 40-50kt. These strong winds will
taper to 35-40 kts by Sunday evening.

Finally, since the KJHW observation has not been reporting, we have
continued with a rarely used NIL TAF for KJHW. Safety concerns have
played a major role in this decision, especially given the continued
potential for low/erratic ceilings at this particular site.

Outlook...

Monday through Wednesday...Mainly VFR.

&&

.MARINE...
A strong area of low pressure tracks northeastward across the Great
Lakes to the Hudson Bay today. This system will bring a round of
high end advisory-worthy conditions, with gale force wind gusts
possible.

After this, a moderate southwesterly flow will result in near-
advisory conditions across eastern portions of the lakes Sunday night
into Monday. Then high pressure will build across the lower Great
Lakes late Monday and Tuesday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory until 10 AM EST this morning for
     NYZ007-008.
     Wind Advisory until 1 PM EST this afternoon for NYZ007-008.
     Wind Advisory from 9 AM this morning to 6 PM EST this evening
     for NYZ004-013-014-020-021.
     High Wind Warning from 9 AM this morning to 6 PM EST this
     evening for NYZ001>003-010>012-085.
     High Wind Warning until 6 PM EST this evening for NYZ019.
MARINE...Small Craft Advisory until 6 PM EST this evening for LEZ020.
         Small Craft Advisory until 11 PM EST this evening for
         LEZ040-041.
         Small Craft Advisory until 6 PM EST this evening for
         LOZ030.
         Small Craft Advisory until 11 PM EST this evening for
         LOZ042.
         Small Craft Advisory until 4 AM EST Monday for LOZ043>045.

&&

$$

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



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