Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 211513

Area Forecast Discussion
National Weather Service Buffalo NY
1113 AM EDT Thu Sep 21 2017

Warm temperatures and dry conditions will persist through the
remainder of the week and the weekend, as high pressure will remain
in place across the region.


Visible satellite imagery and surface observations near midday show
fog and stratus are quickly dissipating. The stratus across the
Finger Lakes will be slowest to burn off eroding from the outer
edges inward through early afternoon.

Today will be a near carbon-copy of Wednesday with perhaps the only
differences being the mid-level ridge strengthening to 588dm and
850mb temps warming a degree to +17C. The high pressure surface and
aloft will keep dry and warm weather in place with high temps again
warming into the low to mid 80s or 10-15 degrees above normal
September levels. In areas where low clouds were found earlier this
morning, took a few degrees off high temps with most of those
locations seeing upper 70s to around 80. Dewpoints holding in the
60s will keep a humid feel to the airmass.

Tonight, more fog will develop with yet another night of near ideal
radiational cooling. Fog will yet again be most prevalent in the
interior Southern Tier Valley locations and in the North Country low-
laying areas near the Black River and Saint Lawrence River Valleys.
Temperatures will again run in the mid 50s inland to the low 60s
near the lakes.


The weather will remain status-quo Friday through the weekend as a
strong and dominant ridge of high pressure surface and aloft remains
parked over the Ohio Valley and eastern Great Lakes. Strong
subsidence and dry air will keep skies mostly sunny each day Friday
through Sunday, with little more than some passing high/thin cirrus
at times. There will likely be river valley fog across the Southern
Tier each late night and morning, with spotty light fog elsewhere in
rural areas.

Temperatures will get even warmer over the weekend as the heart of
warmest temperatures at 850mb cross the region. Expect highs in the
lower to mid 80s at lower elevations Friday and Saturday, then mid
to upper 80s by Sunday. Weak synoptic scale flow and strong
differential heating will allow lake breezes to develop each
afternoon, keeping temperatures a little cooler within a few miles
of the lakes. The clear skies and light winds will allow for fairly
large diurnal swings, with lows Friday night dropping back into the
upper 50s to lower 60s on the lake plains and low to mid 50s across
the interior Southern Tier and east of Lake Ontario. Saturday night
and Sunday night will be milder as low level dewpoints increase.
This will keep lows in the low to mid 60s on the lake plains and
upper 50s in the cooler Southern Tier valleys and Lewis County.


More of the same through the long term period as high pressure
surface and aloft remains dominant across the Ohio Valley and
eastern Great Lakes Monday through Wednesday. It will remain dry
Monday and Tuesday. By Wednesday mid level heights begin to fall
with the approach of an upstream trough. This may erase enough of
the strong mid level cap to allow a few isolated to widely scattered
showers and thunderstorms to develop Wednesday afternoon, mainly
along and inland from the lake breeze boundaries.

Temperatures will remain very warm, with mid to upper 80s again
Monday at lower elevations away from the lakeshores. Temperatures
will begin to pull back just a little by Wednesday as temperatures
aloft begin to cool, but still well above normal and into the lower
80s at lower elevations.

A more significant pattern change will arrive by late next week as
the pattern changes across North America, allowing a longwave trough
to become established across the Great Lakes and eventually New
England. This will force temperatures back to normal by late next
week, and possibly even below normal by the following weekend going
into the first few days of October.


Fog has dissipated at 15z with low status also dissipating from the
outer edges inward. KROC still showing BKN005 at 15z but
extrapolation of visible satellite imagery showing this should clear
around 16z. VFR conditions will then prevail this afternoon into
this evening. Another round of low stratus and fog is again expected
tonight with impacts most likely at KART/KJHW.


Friday through Monday...VFR. Local IFR conditions each late night
and early morning with fog.


High pressure will remain in place across the Lower Great Lakes
right through next weekend. This will provide a long stretch of very
light winds and flat wave action for the rest of the week and
weekend with ideal boating conditions, but not much wind for sailing.





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