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Area Forecast Discussion (AFD)

Issued by Buffalo, NY (BUF)

                            
000
FXUS61 KBUF 161024
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
624 AM EDT Mon Sep 16 2019

.SYNOPSIS...
Weak low pressure will bring some scattered light showers to areas 
south of Lake Ontario early this morning...with this activity then
gradually fading off to our southeast through the rest of today as
the low slides southeastward across Pennsylvania. High pressure will
then bring a prolonged stretch of spectacular late summer weather
for the rest of the week...with temperatures climbing to well above
normal by late in the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of early this morning...weak low pressure was situated over 
western Lake Erie. This low...an attendant surface trough/weak 
frontal boundary draped across western New York...and weak spokes of 
shortwave energy rotating through the mean mid/upper level trough 
aloft continue to generate some widely scattered to scattered across 
areas south of Lake Ontario as of this writing. Meanwhile further to 
the north...the North Country remains removed from the effects of 
the surface low and within a much drier airmass and therefore 
dry...with just some patchy fog here and there. 

As we move through today...the weak surface wave and its attendant 
surface trough/front will sag further southeastward and across 
Pennsylvania...while strong high pressure and much drier air over 
Quebec Province will nose south into our region. This will result in 
the lingering scattered light showers south of Lake Ontario 
gradually fading out from north to south through the rest of the 
day...with widespread morning cloud cover across this same area 
following suit during the afternoon. Otherwise high temperatures 
will be right around normal for mid-September...with most areas 
seeing highs in the upper 60s to lower 70s. 

Tonight the aforementioned surface high will continue to build 
across our region. This will help to scour out any leftover early 
evening clouds across the Southern Tier...thereby leading to mainly 
clear skies for the rest of the night. Coupled with light winds and 
a much drier airmass featuring dewpoints in the 40s...this should 
lead to excellent conditions for radiational cooling...thereby 
allowing overnight lows to fall to the lower to mid 40s across the 
North Country and to the mid to upper 40s in most other locations... 
with only the immediate lakeshores failing to drop below 50 degrees.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
This period will be dominated by an anomalously strong H5 ridge that 
will amplify while slowly drifting east across the Upper Great Lakes 
and Ohio Valley. Having this strong ridge immediately upstream from 
our forecast area will GUARANTEE that fair dry weather will be in 
place through this period.  for the remainder of the time frame. 
Meanwhile...temperatures for both Tuesday and Wednesday will average 
above normal. As for some day to day details...

A large surface high centered over eastern Quebec Tuesday morning 
will gradually extend to the southeast across the Lower Great Lakes 
to the Ohio Valley Tuesday afternoon and night. This will insure 
beautiful weather for Tuesday with sun filled skies helping 
afternoon temperatures reach 70 to 75 for all but the highest 
elevations and portions of the North Country. Another starlit night 
will then follow with mins Tuesday night generally ranging from 45 
to 50...very similar to the previous night. 

A robust shortwave ejecting out of the Intermountain-West Tuesday 
evening will cross the Canadian Prairies before tracking east across 
Ontario Wednesday and Wednesday night. This will effectively shove 
the northern nose of the impressive H5 ridge across Quebec (positive 
tilt) and open the door for a little more noticeable warm advection 
to become established over our forecast area. Meanwhile...the 
corresponding strong surface high will be centered roughly over New 
England. This will maintain gorgeous weather over our forecast area 
with continued clear skies and comfortable temperatures.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
...Spectacular Weather for the end of Astronomical Summer...

There is exceptionally high confidence that we will experience above 
normal temperatures during this period...with near equal assurance 
that it will be accompanied by fair dry conditions (at least thru 
Sat).

The basis for the brimming certainty is the persistent (several days 
worth of model runs)...strong agreement between the GEFS ensembles 
and the operational ECMWF that a 590dm sub tropical ridge will be 
parked over the Lower Mississippi Valley. The ridge will extend to 
the northeast across the Lower Great Lakes...while strong high 
pressure will be in the vcnty of New England. This combination will 
strongly favor sunny days and fair nights with temperatures that 
will average some 5 to 10 degrees above normal. H85 temps that will 
range from 10 to 12c at the start of this three day period will warm 
into the mid teens by the weekend. This will easily support 
afternoons highs in the mid to upper 70s Thursday...with 80s 
expected for Friday through Sunday. 

While we can count on dry weather thorugh at least Saturday...a 
large stacked storm system over central Canada during the weekend 
will eventually push a Pacific based cool front through our region. 
There is some uncertainty as to whether this front will come through 
on Sunday...or Sunday night-Monday...but will include at least the 
chance for some showers as we end the weekend.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
As of early this morning...weak low pressure was situated over 
western Lake Erie. This low...an attendant surface trough/weak 
frontal boundary draped across western New York...and weak spokes of 
shortwave energy rotating through the mean mid/upper level trough 
aloft continue to generate some widely scattered to scattered across 
areas south of Lake Ontario as of this writing. Meanwhile further to 
the north...the North Country remains removed from the effects of 
the surface low and within a much drier airmass and therefore 
dry...with just some patchy fog here and there (including at the 
KART terminal). In terms of flight conditions...a mix of MVFR to 
lower-end VFR conditions continues across much of the region south 
of Lake Ontario...along with embedded pockets of LIFR/IFR. Meanwhile 
the North Country is mainly VFR...save for localized LIFR/IFR in the 
aforementioned patchy fog.

As we move through today...the weak surface wave and its attendant 
surface trough/front will sag further southeastward and across 
Pennsylvania...while strong high pressure and much drier air over 
Quebec Province noses south into our region. This will result in 
lingering scattered light showers south of Lake Ontario gradually 
fading out from north to south through the rest of the day...with 
widespread morning cloud cover across this same area following suit 
during the afternoon. As a result we can expect the current mix of 
flight conditions south of Lake Ontario to gradually improve back to 
VFR from north to south through the course of the day... with this 
improvement taking place toward sunset across the Southern Tier. 
Meanwhile...the North Country will be VFR once any patchy fog 
dissipates by mid morning. 

After that...the aforementioned surface high will provide our area 
with mainly clear skies and predominantly VFR conditions tonight... 
with just some localized valley fog/IFR developing across the 
Southern Tier overnight. 

Outlook... 
Tuesday through Friday...Mainly VFR...with localized IFR 
in Southern Tier valley fog possible each night/early morning.

&&

.MARINE...
A weak surface low over western Lake Erie early this morning will 
sag south of the Lower Lakes Region through the course of today. 
While this system will help induce a brief period of enhanced 
northeasterly winds and choppy conditions from Ripley to Dunkirk on 
Lake Erie and also along the southwestern shore of Lake Ontario this 
morning...conditions will remain below Small Craft Advisory levels. 
Following the departure of this wave...high pressure will then build 
back across our region and bring a return to light winds and minimal 
wave action for the rest of the week.

&&

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

&&

$$

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