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Area forecast discussion
National Weather Service Buffalo New York
952 am EDT Wed Sep 18 2019

Synopsis...
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.

&&

Near term /through tonight/...
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.

&&

Short term /Thursday through Saturday night/...
..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 two...in a closed off cold core
low several hundred miles off the coast. Now for some day to day
details.

An expansive surface high centered along the eastern Seaboard on
Thursday will offer superlative weather across our region...as
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 Friday...as building
heights over the Great Lakes will accompany subtle warming at 850 mb.
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 850 mb temps that are expected to
climb to around 14c. Even so...it 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...850 mb 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 evening...so it might be nest to
plan those activities for earlier in the day.

&&

Long term /Sunday through Tuesday/...
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 arrive...it 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. 850 mb temps by
Tuesday afternoon will be in the vcnty of 6c...so 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.

&&

Aviation /14z Wednesday through Sunday/...
VFR conditions will continue through tonight/taf period with
light winds as surface high pressure remains near the region.

Valley fog in the southern tier may occur again late tonight as
a low level flow of 20 knots mixes drier air in on the Airport
Hill top.

Outlook...
Thursday through Sunday...mainly VFR...with localized IFR in
southern tier valley fog possible each night/early morning.

&&

Marine...
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.

&&

Buf watches/warnings/advisories...
New York...none.
Marine...none.

&&

$$

Synopsis...Hitchcock/Thomas

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