Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 191452
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
952 AM EST Mon Feb 19 2018

.SYNOPSIS...
Low pressure will track into the Upper Great Lakes Tuesday and into
Quebec Wednesday. This will result in periods of rain and a dramatic
warm up for the first half of the week. Temperatures will soar into
the 60s or warmer which would be the warmest weather since last
October.

&&

.NEAR TERM /THROUGH TONIGHT/...
Surface high pressure is off the New England coast this
morning. A southerly flow has increased across the eastern Great
Lakes ahead of the next low pressure system located across the
Central Plains. This system and associated warm front will
approach the lower Great Lakes today bringing wet and
unseasonably warm weather to the eastern Great Lakes today and
tonight.

Warm air advection will continue today as a 40-50kt LLJ advects
moisture into the region. The leading edge of rain has moved
into far SW NY this morning, but much of it will fall apart as
it moves into drier air aloft toward the Niagara Frontier and
Genesee Valley. The more significant area of moisture is
associated with a warm front stretching W-E across the OH
valley. This area is expected to move NE into the region later
this afternoon.

Temperatures will climb into the 50s across the Southern Tier,
portions of the Niagara Frontier and western Finger Lakes
whereas places north of these areas will stay in the 40s. Due to
the warm weather of last week, little to no snowpack exists
across Western New York however, the Tug Hill Plateau still has
considerable amounts of snow water equivalent. See Hydrology
section below for more details on flood potential.

The warm front will move into the forecast area tonight leading to a
mild night with low temperatures climbing further into the 50s. The
LLJ will weaken some across the region as low pressure moves into
Michigan and the warm front moves north into Canada. The axis of
heavier rainfall will also move northward across Lake Ontario and
the North Country this evening and then into Canada by late tonight.
Rain will become more showery tonight as strong warm air advection
continues to draw in anomalously high PWAT air into the region.
Additional rainfall amounts of a half inch to three quarters inch
expected across the Niagara Frontier and North Country. Lesser
amounts expected elsewhere.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Anomalous upper level ridge just off the Southeast coast will
continue to strengthen up to 3 standard deviations above normal
Tuesday and Tuesday night. This will hold the trough in place over
the Southwest CONUS, resulting in a southwesterly mean flow nearly
parallel to frontal boundary extending just to the north of New York
state. Continued surge of moisture along the front will bring the
axis of heaviest rain north and west of the forecast area along the
northern edge of the strong 50 knot plus low level jet.

South of the boundary, much of the area will see plenty of dry time
Tuesday and Tuesday night. Unseasonably warm and near record
temperatures are possible Tuesday with highs well into the 60s
across most locations with a few lower 70s in the Genesee Valley not
out of the question. Coolest temperatures will be along the Lake
Erie and eastern Lake Ontario shorelines with southwest winds
crossing the cool lake waters.

The frontal boundary north of the area will get dragged across the
area as a cold front Wednesday, with widespread rain again shifting
southeast across our region. As the cold front presses southeast
there is a chance that any lingering showers on the backside could
mixing with and changing to some snow showers Wednesday night.

The cold front will bring a return of near normal temperatures in
the wake of the front Wednesday. Temperatures behind the front will
exhibit a non-diurnal trend under cold air advection. Temperatures
will continue to slip back to near freezing Wednesday night.

Total rainfall through Wednesday yields closer to one half an inch
of rainfall over the Finger Lakes increasing toward an inch close to
the Lake Ontario shore. Highest totals are still expected toward the
Saint Lawrence River Valley where and inch and a half could fall.
A Flood Watch remains in effect through Wednesday east of Lake
Ontario with the combination of significant snowmelt and river
rises. This flood potential will include the Black River. See the
Hydrology section below for more details.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Strong dry high pressure is forecast to build over the Great Lakes
Thursday then across New York and New England Thursday night. There
remains a low chance of some lingering rain and snow showers toward
the western Southern Tier on Thursday depending on the speed of the
front but dry weather should be expected elsewhere with some
sunshine also returning. Temperatures will run much closer to normal
with highs only reaching into the mid 30s to perhaps 40 toward the
PA border. Lows will slip into the 20s Thursday night.

12z models continue to show at least two surface waves/frontal zones
crossing our region between later Friday into next weekend. The
closest model agreement seems to point toward Friday night for one
wave where likely POPs have been placed. Otherwise, chance POPs for
rain and at times rain/snow or snow showers run through the weekend
with p-type dependent on diurnal fluctuations in surface temps.
Southerly flow will promote temps around 10 degrees above mid-late
Feb normals.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
VFR conditions will slowly deteriorate this afternoon as steady
rain spread into the region from SW-NE. This will result in
lowering cigs, which will be somewhat offset by downsloping at
BUF/IAG/ROC.

Steady rain continues through at least the evening before
becoming showery overnight or ending altogether over interior
sections near NY/PA state border . LLWS will continue into
Tuesday morning.

Outlook...

Tuesday...Generally VFR to MVFR in showers but IFR across the
North Country in more widespread rain.
Wednesday...MVFR in moderately heavy showers.
Thursday...VFR.
Friday...VFR/MVFR. A chance of rain or snow showers.

&&

.MARINE...
Southerly winds will then increase this morning, with sustained
winds reaching near 30 knots along the Lake Erie near shores, and 20
to 25 knots on the eastern end of Lake Ontario. While the greatest
wave action will be directed into Canadian waters, small craft
advisories are in effect through the afternoon due to the strong
offshore winds alone.

&&

.HYDROLOGY...
There remains a significant risk for flooding in the Black River
Basin. A prolonged period of warm temperatures in the 50s and 60s
will result in significant snow melt, and the Black River basin
still has a significant amount of snow water equivalent in place
despite the brief warm up a few days ago. Although model guidance
has shifted the axis of heaviest rain a bit north and into southern
Ontario province, generally an inch to inch and a half of rain
is likely in the Black River basin with higher amounts possible
on the Tug Hill through mid- week.

The greatest risk for flooding is as the Watertown forecast point
where ensembles show that there is a risk of moderate flooding due
to the widespread (but prolonged) nature of the rain and snow melt.
Latest RFC forecast show the Watertown forecast point still rising
at the end of the forecast, with an increasing risk of flooding
starting on Wednesday. Flooding may be prolonged with the forecast
potentially remaining above or near flood stage for several days.
Boonville and McKeever will respond a bit more quickly, and may
reach flood stage on Wednesday but if they do should crest quickly
and fall within a day or so. Ice jams also may be an issue with
some ice still in place in and along some waterways in the
basin. Meanwhile, snowmelt and rain may result in general
flooding of smaller tributaries in the region.

Elsewhere, there is much less snow pack in place due to recent warm
temperatures. Rainfall amounts in excess of an inch may cause some
creeks in the Buffalo area and lower Genesee basin to approach flood
stage, but model consensus keeps the steadier rains to the north of
these basins with basin averaged between a half inch and an inch.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Flood Watch from late tonight through Wednesday evening for
     NYZ006>008.
MARINE...Small Craft Advisory until 4 PM EST this afternoon for LEZ040-
         041.
         Small Craft Advisory until 4 PM EST this afternoon
         for LOZ043>045.

&&

$$

SYNOPSIS...HSK
NEAR TERM...HSK/ZAFF
SHORT TERM...TMA
LONG TERM...SMITH
AVIATION...HSK/ZAFF
MARINE...APFFEL/CHURCH/HSK
HYDROLOGY...APFFEL/HSK


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