806 
FXUS61 KBUF 131911
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
311 PM EDT Mon Sep 13 2021

.SYNOPSIS...
Mainly dry conditions today before a frontal boundary stalled across 
northern Pennsylvania slowly begins to lift northwards late this 
afternoon. Increased chance of showers and stronger thunderstorms 
tonight. Unsettled weather, with a risk of strong to severe 
thunderstorms at times, will continue through the middle of the week.

&&

.NEAR TERM /THROUGH TUESDAY/...
Frontal boundary remains draped along the NY/PA border this 
afternoon, and is expected to remain in the vicinity until later 
this evening. Outside of a few pop-up showers in the far Southern 
Tier in proximity to the boundary, mainly dry conditions are 
expected to persist though the rest of the day. The boundary will 
start to slowly work back north as a warm front later this evening. 
The remnants of an MCV currently moving into Southern Ontario is 
then expected to expand toward lower Great Lakes late today into 
tonight and produce a round of showers and thunderstorms. Some 
discrepancies remain among the latest guidance on the timing and 
intensity of the convection as it crosses Lake Erie and moves into 
WNY. Current thinking is the first showers reaching into WNY by the 
late afternoon, with the main system impacting the area between 8PM 
and midnight.

There is potential for some stronger storms across WNY to the Finger 
Lakes region tonight once the main convective shortwave reaches the 
area. Should the MCV/storm cluster persist as it treks across the 
lower Great Lakes, 40-50kt westerlies aloft combined with modest 
instability may allow for some severe activity to develop across the 
area. The greatest threat looks to be in closer proximity to the 
still E-W oriented boundary where instability is greatest, with 
SBCAPE values in the 1000-1500J/kg range. The end result will be 
highest chances for severe weather across the Southern Tier, which 
SPC has placed into the 'Slight' risk category, and a 'Marginal' 
risk northwards towards to the Niagara Frontier and Finger Lakes 
region. Main threat with any storms that develop will be damaging 
winds, large hail, and heavy downpours. Upper level ridging works in 
for the second half of Sunday night which should help maintain 
mostly dry conditions for the second half of the night through 
Tuesday morning.

The surface low near Lake Superior will finally kick the stalled 
frontal boundary draped over the region north of the Lower Lakes, 
which will then place us firmly in the warm sector by the afternoon. 
Once the warm front clears the area, storms will then likely focus 
along lake breeze boundaries ahead of the incoming mid-level trough 
and approaching cold front. SPC has our region in a Marginal Risk 
with any stronger storms capable of producing gusty winds and also 
very heavy rain as PW values will range from 1.3 to 1.5 inches. 
Additionally, look for breezy conditions with southwest winds 
gusting to 25-30 knots, especially NE of the Lakes. Highs will be in 
the upper 70s to low 80s.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
Showers and thunderstorms will increase Tuesday night as the 
cold front and shortwave trough move into the region. Large 
scale accent and forcing along this front, in combination with a
strong 40+ knot low level jet will likely produce some strong 
to possibly severe storms. The limiting factor continue to be 
the unfavorable nighttime arrival time of the front across 
Western New York, which will mute its potential, but not 
eliminate the severe weather threat. 

Wednesday, the cold front slowly progresses from west to east across 
eastern Great Lakes. Showers and thunderstorms will slowly work east 
before exiting the entire forecast area late in the day. Drier and 
cooler air will work in the region as showers end from west to east. 

Wednesday night and Thursday, a surface ridge to our north will 
provide dry and quiet weather.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
A tropical storm may be near the Outer Banks/Mid-Atlantic coast 
Friday. A plume of tropical moisture will be confined to the east 
coast however a south-southeast flow Friday will advect some 
moisture into the region with dewpoints in the mid 60s. Daytime 
heating will likely lead to showers developing in the afternoon into 
the evening hours. 

A weak cold front will approach from the north Saturday. This may 
produce a few showers, mainly across the North Country Saturday into 
Saturday evening. Surface high pressure moves across the region 
Sunday into Monday resulting in mostly dry conditions. 

Warmer than normal temperatures expected Friday-Monday with highs in 
the 80s and lows in the 60s.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
Mainly VFR conditions are expected through this afternoon. Tonight, 
some MVFR/IFR CIGS from western NY to Finger Lakes as thunderstorms 
are expected to pass through the area. Some of the storms may be 
strong and produce heavy downpours. CIGS gradually improve to mainly 
VFR in the second half of the night through tomorrow morning.

Outlook... 
Tuesday...Mainly VFR with a chance of showers and thunderstorms. 
Wednesday...Mainly MVFR with widespread showers and some thunderstorms. 
Thursday and Friday...Mainly VFR.
Saturday...Mainly VFR.

&&

.MARINE...
High pressure centered over northern Ontario will start to pass by 
the north on Monday. This will support light and variable winds on 
Lake Erie and light northwesterlies on Lake Ontario. 

As the area of high pressure moves east across Quebec on
Tuesday...a cold front will approach from the Upper Great lakes.
A tightening sfc gradient between the two will lead to
freshening winds on both Lakes Erie and Ontario.

&&

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

&&

$$

SYNOPSIS...PP
NEAR TERM...PP
SHORT TERM...TMA
LONG TERM...HSK
AVIATION...PP
MARINE...JLA/TMA