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Area forecast discussion
National Weather Service Buffalo New York
1034 am EDT sun Aug 25 2019

Synopsis...
high pressure will ridge across the region today and then
slowly move off New England through Monday. This will provide a
dry pattern which will last through Monday night. It will be
warmer and chances for rain will increase ahead of a cold front
which will move across the region early on Wednesday.

&&

Near term /through tonight/...
high pressure will continue to ridge across New York today. There is
still a thin are of moisture below an ~850mb inversion. This
will result in sunny skies becoming partly sunny as isolation
forces boundary layer convection with resulting stratocumulus
drifting east with the prevailing low level flow this afternoon.
Cloud cover may not quite be as extensive inland when compared
to the past two days with both a warmer airmass aloft and a
lacking contribution from the warm lakes. At least it should
be sunny over the lakes. By the end of the day, some cirrus
should start to move in from the SW, but it should be rather
thin.

Meanwhile, temperatures aloft bottomed out yesterday near 5-6c
at 850mb, and now have risen to about 8c. This trend will
continue into the first half of the week. With a warmer overall
airmass and adequate low level mixing, expect highs today to
average in the lower to mid 70s.

The surface high will drift into New England tonight, and this
will maintain dry weather with slowly increasing cirrus. A weak
southeasterly flow will develop, and this will limit but
probably not entirely prevent fog formation again overnight.
Slightly warmer air aloft and the light flow will lead to lows
mainly in the 50s.

&&

Short term /Monday through Wednesday/...
high pressure will remain nearly stationary across northern New
England and the Canadian Maritimes Monday. This will provide one
more pleasant day with comfortable temperatures and humidity levels.
Highs will be in the mid to upper 70s, with some low 70s across the
higher terrain.

A warm front will approach from the west Monday night then cross the
area on Tuesday, as high pressure retreats eastward off the New
England coast. Expect the majority of the area to remain dry on
Monday night, however strengthening warm advection on the nose of 30-
35kt low level jet across western New York Tuesday morning will bring the
chance for some showers to The Finger lakes and points west. The
best warm advection and upper dynamics will remain across western New York
as the warm front finishes pushing northeast of the area Tuesday
afternoon. This should keep most of the shower activity confined to
the western half of Lake Ontario and points south (remaining dry
across Eastern Lake Ontario region), before tapering off later in
the afternoon as the front moves north into southern Ontario. This
should leave behind a brief period of dry weather for the entire
area in its' wake late Tuesday, before a cold front draped across
the central Great Lakes approaches for Tuesday night. Another night
with comfortable temperatures and humidity levels in store, with
lows Monday night ranging from the upper 40s to lower 50s across the
higher terrain, to the mid and upper 50s elsewhere. High
temperatures on Tuesday will be similar to Monday, however there
will be a noticeable uptick in the humidity, especially across
western NY, as dew points rise into the mid 60s.

The cold front will move into western New York by late Tuesday night, then
slowly move east across the remainder of the forecast area during
the day Wednesday. Main threat with this front appears to be a
period of heavy rain just ahead of the boundary with precipitable water values
rising to 1.75-2.00" within a ribbon of deep moisture pooling just
ahead of the cold front on the leading edge of 30-40kt low level
jet. Will keep just the chance for thunder in the forecast as
instability along the front is marginal. Deep southerly flow
combined with increased cloud cover will keep low temperatures
across most areas in the 60s Tuesday night, with some upper 50s
across the higher terrain east of Lake Ontario. Highs on Wednesday
will be in the mid to upper 70s for most areas, with some low 70s
across the higher terrain.

&&

Long term /Wednesday night through Saturday/...
a cooler airmass will briefly settle across the region Wednesday
night and Thursday behind the cold front. Large upper low will be
spinning over the Hudson Bay as large upper trough axis swings
through the area Wednesday night and Thursday. As the cold air
deepens, lingering moisture combined with 850mb temperatures falling
into the upper single digits celsius may be enough to produce some
lake enhanced rain showers downwind of the lakes later Wednesday
night into Thursday morning as steepening lapse rates combine with
lingering moisture. Will have low chance pops near the lakes for
this activity. As happens this time of year, the lakes will 'flip'
by Thursday afternoon due to strong diabatic heating over the land.
This will switch the overnight/early morning land breeze over
to a lake breeze due to subsidence occuring over the lakes as
the land heats up and becomes warmer than the water surface.
This will force this boundary back inland where it will
intersect steep low level lapse rates due to cold air just off
the deck. When combined with low level moisture trapped under a
subsidence inversion, these features will produce stratocumulus
decks along and inland of any lake breeze boundaries. Some of
these decks may grow thick enough where instability is greatest
to produce a few showers during the afternoon (especially across
the higher terrain).

Warmer air will quickly move back into the region Thursday night
into Friday, as southwesterly flow develops between clockwise flow
around surface high pressure moving east across the mid Atlantic,
and well out ahead of a cold front to the northwest of the area.
This should provide mainly dry weather during this period.

This weak cold front will cross our region Friday night or Saturday.
There is some disagreement amongst the models as to the timing of the
frontal passage this far out in the future. Will go with general
chance pops at this point until model consensus comes into better
alignment.

Temperatures will not stray much from normal, with highs in the 70s
and lows in the mid to upper 50s through this period.

&&

Aviation /15z Sunday through Thursday/...
high pressure will dominate with mainly VFR flight conditions
and light winds through tonight. Diurnal cumulus will by
afternoon, but cloud bases should be around 4k ft and in the
VFR flight category. These clouds will dissipate late afternoon
with widespread VFR conditions through this evening. Patchy
valley fog will develop late tonight, but will probably remain
east of the kjhw terminal.

Outlook...

Monday...mainly VFR with nothing more than southern tier valley
fog producing local IFR conditions.

Monday night and Tuesday...mainly VFR.
Tuesday night through Thursday...VFR with some short periods of
MVFR from showers and thunderstorms.

&&

Marine...
relatively light and variable winds with corresponding light wave
action are expected into Monday as surface high pressure moves
slowly east across the region.

&&

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

&&

$$

Synopsis...apffel
near term...apffel/zaff

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