Area Forecast Discussion
Issued by NWS Buffalo, NY

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710
FXUS61 KBUF 232004
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
404 PM EDT MON MAY 23 2016

.SYNOPSIS...
Summer is on its way with highs slowly climbing through the 70s and
into the 80s by the weekend.  After a dry day across Western New
York on Tuesday, a scattered shower or thunderstorm will be possible
each day leading up to and into the Memorial Day weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
With a slow moving upper level low over the Mid Atlantic region, the
flow throughout the atmospheric column is out of the northeast. This
fairly unusual pattern overhead will break down as a ridge upstream
begins to move east toward NY.  This will eventually usher in our
first real taste of summer as southwesterly flow begins to advect
warmth and moisture toward the region.  However, we should be able
to squeak out at least one more cool night (50s and perhaps upper
40s in portions of the Southern Tier) tonight under clear skies
while high pressure moves through the OH valley. There may be just
enough low level moisture in the Southern Tier for a return of
valley fog late tonight.   On Tuesday, expect a little less inland
cumulus with a drier low level airmass.  Highs should end up a few
degrees warmer as well.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
An upper level low across New England on Tuesday night will
gradually exit into the Canadian Maritimes as ridging expands from
the Southeastern states into the Mid-Atlantic. Our region will be
located at the top of the 500 mb ridge with a westerly flow aloft
periodically advecting disturbances across the area.

Tuesday evening should start off dry with a consensus of guidance
tracking a narrow 500 mb ridge axis across the region. After this a
weak disturbance will move across or pass just north of the area
late Tuesday night into Wednesday morning. Timing is unfavorable
from a diurnal heating and instability perspective, which will lower
the chances for showers with this wave. On Wednesday afternoon
marginal instability showers and thunderstorms should develop mainly
on lake breeze boundaries. Consensus QPF is limited with higher
resolution guidance capturing the stabilizing influence of the lakes
best. Forecast confidence is above average due to the good model
agreement handling this wave for the 00Z and 12Z runs of the
NAM/GFS/GEM/ECMWF.

Following a lull Wednesday evening another more significant wave
will cross the region on Thursday. This will originate from a
shortwave which will help lift a warm front and advect moisture into
the region. PWAT values are forecast to increase to around 1.75
inches. Timing is also more favorable to take advantage of
instability associated with daytime heating, especially from the
Finger Lakes Region into Central New York where model consensus
brings the wave across during the afternoon hours. Increasing
instability supports a chance of thunderstorms across the entire cwa.
It is also worth noting that low level wind fields will be weak
suggesting that there may be some slow moving storms which could
produce locally heavy rainfall. Any threat for flooding is somewhat
mitigated by recent dry weather.

Temperatures will be above normal during the period, especially on
Thursday when 850mb temperatures are forecast to reach +15C.
Forecast highs are above consensus temperature guidance with
temperatures inland of the lake breeze expected to reach the lower
80s in most areas.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Latest medium range models and ensembles continuing to suggest a
summery weather pattern is on the way, just in time for Memorial Day
weekend, complete with increasing humidity and daily chances for
mainly afternoon showers and thunderstorms.

The overall pattern will evolve with the forecast area located near
the northern periphery of a large scale ridging centered just off
the mid-Atlantic coast. The placement of the ridge will not only
allow a steady feed of warm and moist air into the region, but will
also supply numerous shortwaves riding over the top of the ridge as
forcing mechanism for showers and thunderstorms especially during
peak diurnal heating. It is hard to put a real timing in the
extended with this type of pattern. Therefore, will maintain chance
category probabilities through the period. The greater chances will
likely be from inland lake breezes over the northern Niagara
Frontier and hilly region east of Lake Erie...and higher terrain
east of Lake Ontario.

At 500 hPa heights will slowly increase through the long term
period...and at 850 hPa...air temperatures will range from +14 to
+17c through the period. Warmest 850 hPa temperatures will come
Saturday...during the peak height of the upper level ridge. The
southerly flow will also build the humidity through this period with
uncomfortable levels reached by the end of the week. Dewpoints will
reach to around 60F to the lower 60s. Air temperatures will likely
increase a degree each day...as 500 hPa heights slowly increase.
Afternoon highs will reach into the upper 70s to lower 80s. Would
not rule out some mid-80s by the weekend for the Genesee Valley and
for lower elevations south of Lake Ontario. There will not be much
airflow under the ridge...but a SW wind will likely develop each
day...keeping the City of Buffalo a few degrees cooler...with the
cooling extending out to near the airport. Along the immediate Lake
Ontario shoreline...and then the western Saint Lawrence Valley...air
temperature will be a few degrees cooler owing to the still cool
eastern Great Lakes. Overnight lows will drop back into the lower
60s...and with a similar airmass all four nights should have similar
overnight lows.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
VFR conditions are expected through Tuesday as a slowly ridge moves
toward the Eastern Great Lakes region.  There be some inland valley
fog over the Southern Tier again tonight, although coverage should
be even more sparse.  Look for mainly clear skies with little if any
cumulus field on Tuesday.

Outlook...
Tuesday Night and Wednesday...VFR.
Thursday through Saturday...Mainly VFR with a chance of showers and
thunderstorms.

&&

.MARINE...
High pressure will build into the central Great Lakes tonight
through Tuesday.  This will maintain light winds and flat wave
action for the next few days. The tranquil pattern will continue
through the end of the week, although a few thunderstorms may
produce locally higher winds and waves at times each day from
Wednesday through next weekend.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...ZAFF
NEAR TERM...ZAFF
SHORT TERM...APFFEL
LONG TERM...TMA
AVIATION...HITCHCOCK/ZAFF
MARINE...HITCHCOCK



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