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FXUS61 KBUF 181023

Area Forecast Discussion
National Weather Service Buffalo NY
623 AM EDT Wed Sep 18 2019

An area of strong high pressure will provide us with a prolonged 
stretch of magnificent late summer weather for the rest of the week, 
with temperatures climbing to well above normal by late in the week. 
The next chance of rain will not arrive until Sunday night.


All is quiet for the Eastern Great Lakes region this early 
morning...with an autumn chill to the air as temperatures dip into 
the lower 50s...and inland 40s. 

Clear skies to start the day will only have a few wisps of passing 
cirrus through the daylight hours. 

Strong surface high pressure just to our east, with a strong 500 hPa 
ridge axis over our region will allow for afternoon temperatures in 
the low to mid 70s (about 5F above normal). 

These clear skies at night will again promote excellent radiational 
cooling conditions with lows in the lower 50s to inland mid 
40s...and Southern Tier fog forming in the river valleys.


...Stunning Weather to End Meteorological Summer...

A mid latitude blocking pattern will be in place across North 
America during this period...and fortunately for us...we will be 
situated under one of the dominant ridges. This will GUARANTEE sunny 
days and fair nights with temperatures that will be more typical of 
early August than the final days of meteorological summer. The key 
to the block will be an anomalously strong 600dm ridge that will be 
anchored over the open Atlantic (roughly 30N 45W). This will 
temporarily keep the flow from being progressive back across the 
United States. Our interest will though lie in a second (590dm) 
ridge that will amplify during the period over the Ohio Valley and 
Great Lakes region. An interesting note is that the remnants of 
Humberto will be caught between the a closed off cold core 
low several hundred miles off the coast. Now for some day to day 

An expansive surface high centered along the eastern seaboard on 
Thursday will offer superlative weather across our 
fairly strong subsidence within a dry airmass will support wall to 
wall sunshine. While temperatures are expected to climb to between 
70 and 75 across the region...light winds and the presence of a 
staunch subsidence inversion may prevent us from fully tapping into 
a +12c H50 airmass. 

The center of the sfc high will migrate to the Mid Atlantic region 
Thursday night. Given mainly clear skies and light winds over our 
forecast area...decent radiational cooling will offer us another 
relatively cool night with mins ranging from the mid 40s across the 
Southern Tier and in Lewis county to the mid 50s across a large 
chunk of the lake plains. It almost goes without saying that there 
will once again be valley fog across the Srn Tier and portions of 
the Finger Lakes region.

Another beautiful day can be anticipated for building 
heights over the Great Lakes will accompany subtle warming at H85. 
As was the case from the day before (Thurs) though...a weak flow 
with a fairly strong subsidence inversion still in place will keep 
us from taking full advantage of H85 temps that are expected to 
climb to around 14c. Even will be a bit warmer in the 
afternoon with temperatures generally ranging from 75 to 80. 

A toothless backdoor cold front will slip south from the Ottawa 
Valley Friday night and Saturday morning. A lack of moisture and 
general lack of forcing will make this more of a novelty rather than 
an actual weather producing feature. From this vantage the only 
impact will be the encourage a little more cloud cover...but that 
should spoil the trend of very pleasant late summer weather. In 
fact...the now progressive mid level ridge will push east during the 
course of Saturday...and this will effectively shove the sfc 
boundary back to the north into Quebec. Meanwhile...H85 temps may 
further climb to 15/16c and with warming also in the lower 
levels...the subsidence cap will effectively disappear. NOW we will 
have the ability to take advantage of the full airmass which should 
support afternoon temperatures of 80 to 85 across the lake plains 
and certainly the Genesee Valley. 

A deepening south-southwest flow ahead of an approaching frontal 
boundary will add some humidity to the mix on Sunday. Dew points in 
the low to mid 60s by midday will accompany afternoon highs in the 
low to mid 80s on a day that could very well be the warmest day for 
the remainder of the calendar year. That might be a bold call...but 
it won't be a stretch to say that it will feel every bit like summer 
as Mother Nature ends meteorological summer on a high note. Fall 
will officially begin at 3:50 the following morning. Otherwise... 
fair weather will persist across the vast majority of the region 
with only a gradual increase in cloud cover. It is worth noting that 
a shower cannot be ruled out though for the far western counties and 
also for the North Country towards it might be nest to 
plan those activities for earlier in the day.


This period will certainly be more active than the previous five 
days...and while temperatures will still average above normal...they 
will most certainly trend lower to more seasonable levels.  

Unlike the week leading into this period...guidance is not in lock 
step with the handling of the systems that will impact our weather. 
Specifically...there are differences with the speed of the two 
boundaries that will generate some showers over our region Sunday 
night into Monday night. The general consensus is that a pre frontal 
sfc trough will push across the region Sunday night...immediately 
followed by an actual cold frontal boundary on Monday. While there 
are timing issues...there is fairly high confidence that likely pops 
will work for the 24 hour period ending Monday evening. 

An interesting note is that the remnant moisture from once Tropical 
Depression/cyclone Imelda will get caught up in the general 
westerlies and advect from the Mississippi Valley across the Upper 
Mid West to the Upper Great Lakes by Sunday morning. While guidance 
favors that this moisture will largely push on past our region 
before the frontal systems is not out of the question 
that it could enhance some of the rainfall Sunday night. 

Gradual improvement is then anticipated Monday night and Tuesday in 
the wake of the supporting mid level shortwave trough. H85 temps by 
Tuesday afternoon will be in the vcnty of it will certainly 
be cooler. Afternoon highs Tuesday should be in the upper 60s to 
near 70...which will still be a couple ticks above normal.


For the 12Z TAFS VFR flight conditions are found, and these 
conditions are expected to continue through the TAF period with 
light winds as surface high pressure remains near the region.

Valley fog in the Southern Tier this early morning should stay just 
to the east of KJHW...and possibly again late tonight as a low level 
flow of 20 knots mixes drier air in on the airport hill top.

Thursday through Sunday...Mainly VFR...with localized IFR in 
Southern Tier valley fog possible each night/early morning.


High pressure will provide our region with light winds and minimal 
wave action for the rest of the week. The one minor exception will 
be on Lake Erie and western Lake Ontario, where a brief period of 10-
15 knot northeast winds will develop this afternoon, bringing waves 
up to around 2 feet briefly.





NEAR TERM...Thomas

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