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Area Forecast Discussion (AFD)

Issued by Buffalo, NY (BUF)

                            
251 
FXUS61 KBUF 150637
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
237 AM EDT Wed Aug 15 2018

.SYNOPSIS...
Weak high pressure will build in from the Upper Ohio Valley this 
morning. This will support dry but humid weather for today. 
Widespread unsettled weather will then return for the second half of 
the week when a complex area of low pressure will cross the Lower 
Great Lakes.

&&

.NEAR TERM /THROUGH TODAY/...
Surface ridging is extended north across western NY early this 
morning stemming from high pressure centered over West Virginia. 
Infrared satellite imagery shows clear skies over much of western NY 
into the Finger Lakes with the back edge of widespread cloudiness 
continuing to clear east across the eastern half of NY. Some patches 
of fog have developed with the clear skies and light winds. One 
patch is over the Boston Hills, with some southern Tier river valley 
fog developing as well. KART also is reporting some fog east of Lake 
Ontario. Otherwise...overnight lows will range from the lower to mid 
60s across interior portions of the Southern Tier/North Country to 
the mid and upper 60s across the Lake Plains...with the Lake Erie 
shoreline of Chautauqua County likely not dropping below 70. 

After sunrise...the upper level ridge will broaden and flatten out 
as it passes through our longitude...though will nonetheless still 
remain strong enough to promote a mainly dry day for the most 
part...albeit with continued rather warm and humid conditions.
The possible exceptions to the mainly dry weather will come during 
afternoon peak heating of our warm and humid airmass...when 
developing lake breeze boundaries could lead to a few isolated to 
widely scattered showers and storms south of Lake Ontario...and an 
approaching weak frontal boundary may trigger some additional 
scattered convection across the North Country and Saint Lawrence 
Valley. Otherwise...we can expect afternoon highs ranging from the 
lower 80s across the higher terrain to the mid and upper 60s across 
the lower elevations...with these accompanied by muggy dewpoints in 
the mid to upper 60s.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
Wednesday evening a weak cold front will brush across the Saint 
Lawrence Valley and North Country, then wash out as it moves east 
across northern NY. A few widely scattered showers and isolated 
thunderstorms may linger into the evening east of Lake Ontario, 
otherwise the remainder of the region will be dry through the 
evening. A few showers may approach Western NY by daybreak Thursday, 
with clouds on the increase for Western NY ahead of the next system. 
It will be a warm and muggy night, with lows in the upper 60s to 
around 70 on the lake plains, and low to mid 60s in the cooler 
Southern Tier valleys and Lewis County.

Thursday a mid level shortwave will move out of the Ohio Valley and 
into Lower Michigan. Warm advection, moisture transport, and a 
leading low amplitude shortwave will push out ahead of the main 
trough and into Western NY through the course of the day. This will 
spread showers and scattered thunderstorms into Western NY during 
the morning, reaching the Genesee Valley and western Finger Lakes 
during the afternoon. Most of the day should remain dry east of Lake 
Ontario with a chance of a few showers toward evening. Highs will 
reach the lower to mid 80s in most locations prior to the arrival of 
steadier showers.

Thursday night and Friday the mid level trough will move from Lower 
Michigan into southern Ontario, with a surface low tracking over or 
just north of Lake Ontario. Moisture will continue to be transported 
into the area with PWAT reaching 2 inches. Initial forcing from warm 
advection Thursday night will transition to forcing from the mid 
level trough passage and associated pre-frontal trough by Friday. 
The forcing and quality moisture will support several rounds of 
showers and scattered thunderstorms. The anomalously high PWAT will 
support a risk for locally heavy rain and flooding. It will become 
very muggy, with dewpoints around 70 Thursday night and Friday. Lows 
will only drop into the upper 60s to lower 70s Thursday night, with 
clouds and showers keeping highs in the upper 70s to lower 80s 
Friday. 

The system will slowly exit the area Friday night as the mid level 
trough eases southeast across the eastern Great Lakes. The heavy 
rain risk will end in the evening, with lingering showers slowly 
tapering off from northwest to southeast.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Saturday the late week system will weaken and slowly exit off the 
New England coast. There may be enough lingering moisture and weak 
forcing to support a few more scattered showers or an isolated 
thunderstorm, mainly across the Southern Tier and points southeast 
and east of Lake Ontario. A somewhat less humid airmass will build 
into the region Saturday, with highs ranging from 75-80.

Sunday through Monday weak high pressure will bring a return to dry 
weather across the eastern Great Lakes. It will remain warm, with 
highs in the lower 80s Sunday and mid 80s by Monday across lower 
elevations. Lows will generally be in the 60s on the lake plains and 
50s in the cooler Southern Tier valleys and Lewis County.

The next system will move into the Great Lakes later Monday night 
and Tuesday. A mid level trough and associated cold front are 
forecast to cross our region Tuesday, with the next chance of rain.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
A narrow area of surface ridging extends of western NY early this 
morning. This has brought much drier air in with clear skies at all 
TAF sites for 06z. Across parts of the Southern Tier and east of 
Lake Ontario patches of fog (MVFR to IFR conditions) have begun to 
form. KART has already reported IFR VIS but lifted quickly to MVFR 
VIS and KJHW will likely also dip vis down when fog develops later 
this morning. 

After sunrise...any fog across the Southern Tier/North Country and 
attendant restrictions will dissipate early in the morning with 
renewed diurnal heating and mixing...leaving behind largely dry VFR 
conditions for the balance of the day. The possible exceptions to 
this will come during afternoon peak heating of our warm and humid 
airmass...when developing lake breeze boundaries could lead to a few 
isolated to widely scattered showers and storms south of Lake 
Ontario...and an approaching weak frontal boundary may trigger some 
additional scattered convection across the North Country and Saint 
Lawrence Valley. Within any of these...brief/localized reductions to 
sub-VFR conditions will be possible. 

Outlook... 

Thursday and Friday...Showers and thunderstorms with areas of 
attendant MVFR likely.. Saturday...Mainly VFR with a chance of a 
shower across interior sections.
Sunday...VFR.

&&

.MARINE...
Aside from a few additional possible showers and storms across the 
Saint Lawrence Valley Wednesday afternoon and evening as a weak cold 
front crosses the region...there will otherwise be little in the way 
of marine concerns through midweek with both winds and waves 
expected to remain safely below Small Craft Advisory levels. More 
unsettled conditions will then return for Thursday and Friday as 
another wave of low pressure crosses the Lower Lakes Region and 
brings a renewed potential for showers and thunderstorms.

&&

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

&&

$$

SYNOPSIS...RSH/Smith
NEAR TERM...JJR/RSH/Smith
SHORT TERM...Hitchcock
LONG TERM...Hitchcock
AVIATION...JJR/RSH/Smith
MARINE...JJR/RSH/Smith