Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 241053
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
653 AM EDT Mon Apr 24 2017

.SYNOPSIS...
Expansive high pressure stretching from Hudson Bay to New England
will provide another beautiful day across our region today...as we
will once again enjoy sun filled skies. The fair weather will
gradually come to an end late tonight and Tuesday though when
showers from a coastal storm will spread back across our forecast
area. It will then become summer like by mid week...as the mercury
will soar into the 70s for Wednesday and well into the 80s Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
A weak cool frontal boundary will wash out across the western
counties early this morning...while expansive high pressure centered
over the western shore of Hudson Bay will extend to the southeast
across the St Lawrence Valley and New England. This will set the
stage for yet another beautiful day across our forecast area...as
subsidence associated with the sprawling area of high pressure will
combine with a dry airmass to provide us with sun drenched skies.

In regard to temperatures today...most areas will experience
readings that will be relatively close to normal. The exception will
be across the Southern Tier where the mercury will climb to roughly
10 deg f above typical late April values. H85 temps warming to
between 6 to 8c will combine with the wealth of sunshine to support
max temps in the lower 70s f across much of the Southern Tier...
while readings will generally be in the low to mid 60s elsewhere.
The coolest areas this afternoon will be across the counties that
border the south shore of Lake Ontario. In these areas...a
persistent northeast wind will keep temperatures from climbing out
of the 50s.

Tonight...the axis of the large surface high will push east to the
Canadian maritimes while a nearly stationary storm system will hover
along the Southeast coast. This synoptic set up will encourage a
deep southeasterly flow to become established over the Mid Atlantic
states...which in turn will advect increasing amounts of Atlantic
moisture back up across our forecast area. As clouds lower and
thicken from the southeast later tonight...an accompanying swath of
moderately strong warm advection could generate enough lift for some
sprinkles or legitimate showers as we make our way through the wee
hours of the morning. Otherwise...the vast majority of tonight will
be problem free.

After two nights of temperatures in the 30s...we will experience a
reprieve from the chilly air as the increased cloud cover will help
to hold the mercury in the 40s. The exception will be across parts
of the eastern lake Ontario region where there could be some upper
30s.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
Tuesday and Tuesday night a cutoff upper level low and its associated
surface reflection will meander its way northeastward along or just
offshore of the Carolina and Virginia coastlines. A feed of Atlantic
moisture wrapping around the northern flank of this system will bring
overcast skies and the likelihood of a few showers to most areas Tuesday
morning...with shower chances then diminishing fairly quickly from west
to east Tuesday afternoon and Tuesday night as the deeper moisture and
responsible forcing slide off into New England. Rainfall amounts out of
this system will be fairly light with totals ranging from a tenth of an
inch or less south of Lake Ontario to one to two tenths of an inch
across the North Country...so do not expect Tuesday to be a washout by
any means...particularly across far WNY where the rain will likely only
last a few hours. Temperature-wise...highs on Tuesday will range from
the mid to upper 50s across the North Country to the mid 60s across the
Lake Erie lake plain...where conditions will be relatively drier and
where a southeasterly downslope flow will come into play. Lows Tuesday
night will then range from the upper 40s to lower 50s Tuesday night...
with the warmest readings again along the Lake Erie lake plain due to
continued modest downsloping.

On Wednesday sharpening upper level ridging will be found across our
region...in between the weakening cutoff low lifting just offshore of
the Mid Atlantic coastline...and the next mid and upper level trough
developing into the Great Lakes and Upper Midwest. The combination of
strong subsidence under this ridge...increasing amounts of sunshine...
and warm advection attendant to a continued modest southeasterly
downslope flow will help drive 850 mb temps up to between +9C and +12C
across our region...which should in turn allow for a pretty nice day
with highs warming into the 70s in most places...with the warmest
overall readings (mid-upper 70s) found across areas south of Lake
Ontario.

During the second half of this period...an elongated modest surface low
will gradually lift from the Great Lakes into western Quebec...and will
eventually pivot its trailing cold front across our region Thursday
night. With the marked slowing trend of this system having continued
over the last 24 hours...it now appears that Wednesday night and the
vast majority of Thursday will both remain dry...with just a low-end
chance for showers/thunderstorms reaching extreme far western New York
late the day Thursday...before the front and its scattered convection
work across the region Thursday night.

With steady warm air advection thus persisting across our region right
through Thursday under a deepening southerly downslope flow regime...
temperatures both Wednesday night and Thursday will easily be more
typical of midsummer than of midspring. Speaking more specifically...
lows Wednesday night will struggle to drop below the mid 50s to lower
60s...with the combination of 850 mb temps of +15C to +17C...partly to
mostly sunny skies...and the aforementioned downsloping then allowing
temperatures to surge all the way into the lower to mid 80s areawide
on Thursday. High temperature records for April 27th are 84 at Buffalo
(1984)...86 at Rochester (1990)...and 85 at Watertown (2009)...with it
appearing increasingly likely that the records at Buffalo/Rochester
will at least be approached if not threatened. After that...modest cool
air advection setting up behind the cold frontal passage will allow lows
to fall back into the mid and upper 50s Thursday night...though such
readings will still be some 15-20 degrees above late April normals.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
While a few leftover showers and isolated storms will be possible
across our southeastern periphery as the front departs our region on
Friday...the last day of the work week will mostly just feature a return
to drier and cooler weather as high pressure and drier/cooler air build
into the region from the Upper Great Lakes. This said...temperatures
will still remain well above normal...with daytime highs still expected
to range between the mid 60s and lower 70s.

Moving on into next weekend...the medium range guidance packages
continue to suggest that the next frontal system will work into our
area next weekend...with a warm frontal boundary extending into our
region between Saturday and Saturday night...then lingering across
the region through most if not all of Sunday. This will translate into
general chances of showers and thunderstorms across our region both
weekend days...for which broadbrush low-mid range chance PoPs will be
in play. Meanwhile temperatures will remain notably above average...
though the exact magnitude of these departures will be highly dependent
upon the exact position of the warm front...as this feature will mark
the dividing line between pleasantly warm spring conditions to its
north...and downright midsummerlike warmth to its south.

Looking out just beyond the end of this period...it still appears
that the warm front may finally lift north of our region Sunday night...
possibly setting the stage for another round of 80+ degree temperatures
next week Monday.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
High pressure centered near Hudson Bay will extend to the south
across New England this afternoon...and this will allow for another
beautiful day for flying with nearly cloud free skies.

The fine VFR weather will continue through at least the first
half of tonight...then clouds will lower and thicken from the
southeast during the wee hours of Tuesday morning. There may
even be some light showers over the western counties by the end
of the night.

Outlook...

Tuesday...Mainly VFR with showers likely.
Wednesday...VFR.
Thursday...VFR/MVFR with a chance of showers and thunderstorms.
Friday...Mainly VFR with a slight chance of showers and
thunderstorms.

&&

.MARINE...
High pressure centered near Hudson Bay will nose southeast across
the St Lawrence Valley and New England during the midday and
afternoon. This will generate a northeasterly flow across the Lower
Great Lakes region...with small craft advisory conditions expected
in the nearshore waters of Lake Ontario from the IAG River to Mexico
Bay. The choppiest conditions will be west of Irondequoit Bay.

As the axis of the surface high pushes east to the Canadian
maritimes tonight...the flow will veer to the east and this will
redirect the choppiest conditions into Canadian waters. Weaker winds
and less wave action will be found on Lake Erie.

A general east to southeast flow will remain in place across the
Lower Great Lakes Tuesday and Wednesday...as a very slow moving
coastal low will be found along the coast of the Carolinas.
Again...the choppiest conditions will be found in Canadian waters so
no additional marine related flags are anticipated.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for
         LOZ042>044.

&&

$$

SYNOPSIS...RSH
NEAR TERM...RSH
SHORT TERM...JJR
LONG TERM...JJR
AVIATION...RSH
MARINE...RSH



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