Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 162031
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
431 PM EDT Mon Apr 16 2018

.SYNOPSIS...
Sprawling low pressure draped across our region will gradually
consolidate while slowly pushing northeastward into Quebec and New
England tonight and Tuesday. This system will keep unsettled weather
and well below normal temperatures across our region right through
Tuesday, with occasional rain and wet snow, which will produce some
minor snow accumulations across the higher terrain. Another low
pressure system will then bring another round of rain and a little
wet snow Wednesday night into Thursday, before drier and quieter
weather arrives for the end of the week and upcoming weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
Radar imagery showing a plume of moderate to briefly heavy rain
across the eastern Lake Ontario region late this afternoon along a
slowly advancing cold front and associated deep plume of moisture.
This rain will continue through early evening before the cold front
moves east, and the plume of moisture breaks down and re-focuses
across southern new England.

Farther west, a widespread area of deep wrap around moisture and
forcing associated with the mid level closed low is found across
Western NY. Increasing cold advection behind the cold front has
changed the rain to wet snow in many areas. The steady wet snow will
continue through early evening, with up to an inch accumulation on
the grassy surfaces. By mid to late evening, the remaining wet snow
and rain will become lighter and more intermittent.

With respect to the Flood Watch...that was cancelled earlier this
afternoon. The latest round of river forecasts continue to show that
any crests along area waterways will remain below flood stage. While
a few of the Buffalo and Rochester area creeks will still likely get
to action stage over the next couple of days and will still need to
be monitored (along with some of our typical lower-lying trouble
spots)...at this point the threat of more widespread flooding has
lowered plenty enough to allow for the cancellation of the Watch.

Tonight and Tuesday the elongated area of low pressure will
gradually consolidate while pushing northeastward into Southern
Quebec and New England. In its wake...a deep/moist cyclonic flow of
progressively colder air will linger across our region...which will
maintain well below average temperatures and continued unsettled
conditions...with the widespread synoptic precipitation from this
afternoon becoming more showery in nature and also becoming more
concentrated east of the lakes...where an upslope westerly flow will
provide orographic enhancement. At the same time...the arrival of
colder air will force ptype to transition to more in the way of wet
snow over time tonight...with a rain/wet snow mix then expected
again on Tuesday as boundary layer temperatures warm a bit owing to
diurnal influences. At this point it still appears that the higher
terrain will become cold enough for some minor slushy accumulations
of 1-3 inches east of Lake Erie and an inch or less east of Lake
Ontario tonight...with another 1-2" then possible during the day
Tuesday. Meanwhile across the lower elevations more marginal
temperatures will result in minor accumulations of under an inch
through the period...and mostly between tonight and early Tuesday at
that. With respect to temperatures...expect tonight`s lows to range
from the upper 20s to mid 30s across far western New York...with
readings ranging through the 30s elsewhere. Highs on Tuesday will
then range from the mid 30s across the higher terrain to the upper
30s and lower 40s across the lower elevations.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
Cyclonic large scale flow will continue over the area through
Tuesday night as the decaying system that is trudging into Lake
Ontario today will have only moved northeastward a couple hundred
miles by that point as it continues to decay with its frontal
structure becoming further occluded. The fact that multiple mid-
level vort maxima will be doing the Fujiwhara will not help matters
any either, as the large scale pattern seems fully content to really
not evolve much at all. Even still, with modest cold advection
continuing over the region and deeper surface moist layer remaining,
especially over the north country, snow showers downwind of the
lakes will continue. Given marginal boundary layer temperatures,
light accumulations really should only be expected in the higher
terrain.

By Wednesday, even while northwesterly large scale flow continues
over the north country, deeper moisture from warm advection will be
advancing northward from the Ohio Valley. In the interim, there
looks to be an exceedingly short window during which layer RH values
fall off enough that we should see some amount of clearing during
the second half of the day Wednesday. However, this will be fleeting
as moisture from the southwest will quickly increase into the
evening.

With southwesterly flow increasing, the atmosphere should become
sufficiently warm such that general light rainfall will develop from
southwest to northeast on Wednesday night and continue into
Thursday. Most of the forcing with this system will be from 500 hPa
on downward as upper jet dynamics really do not look to play a
part and the pronounced theta-e ridge at 850 hPa does all of the
heavy lifting. That said, PWAT values with this upcoming system
are about a half an inch lower than the one that moved through
over the weekend, so far lighter QPF is expected.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Cold advection in the wake of Thursday`s system will again allow for
northwesterly large scale flow snow shower chances to return. This
mid-week system does not look to be carrying a large pool of cold
air behind it, however. Thus, snow shower chances taper off fairly
quickly into the end of the work week.

Ridging will finally start to edge into the Great Lakes by the
weekend. This will allow for drier conditions to become very common.
The sun should also start to make its cameo across the region. That
said, the ridge axis on basically all ensembles fails to really
advance through the area, thus while moderating temperatures and
clearing will be common, substantiating warming even to values
above normal looks unlikely during the long term period.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/...
Low pressure draped across our region will gradually consolidate
while pushing northeastward into southern Quebec and New England
tonight and Tuesday. As this occurs...widespread rain out ahead of
this system this afternoon (mixed with wet snow across far western
New York) will become more showery in nature and more concentrated
east of the lakes tonight through Tuesday. At the same time...the
arrival of colder air will force the precipitation to transition to
more in the way of wet snow over time tonight...with a rain/wet snow
mix then expected again on Tuesday as boundary layer temperatures
warm a bit owing to diurnal influences.

Owing to both the above and plentiful low level moisture lingering
behind this system...widespread IFR to MVFR conditions will persist
across the region through Tuesday. The worst overall conditions will
be found in the wake of the low this afternoon...and then east of the
lakes tonight and Tuesday.

Outlook...
Wednesday...Lingering rain/snow showers and IFR/MVFR east of Lake
Ontario diminishing...otherwise mainly VFR.
Wednesday night and Thursday...MVFR/IFR in rain...which may initially
be mixed with some wet snow across the North Country.
Friday...Mainly VFR with a chance of rain/snow showers.
Saturday...Mainly VFR.

&&

.MARINE...
Low pressure draped across our region this afternoon will gradually
consolidate and drift northeastward across Quebec and New England
through midweek. In its wake...a brisk southwesterly flow of colder
air will continue to support fairly widespread Small Craft Advisories
through Tuesday night...and into Wednesday across eastern portions of
Lake Ontario.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 11 PM EDT Tuesday for LEZ020.
         Small Craft Advisory until 5 AM EDT Wednesday for LEZ040-
         041.
         Small Craft Advisory until 11 PM EDT Tuesday for
         LOZ030.
         Small Craft Advisory until 11 AM EDT Wednesday for LOZ042-
         043.
         Small Craft Advisory until 8 PM EDT Wednesday for LOZ044-
         045.

&&

$$

SYNOPSIS...Hitchcock/JJR
NEAR TERM...Hitchcock/JJR
SHORT TERM...Fries
LONG TERM...Fries
AVIATION...JJR
MARINE...JJR



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