Scientific Forecaster Discussion
fxus61 kbuf 191043
Area forecast discussion
National Weather Service Buffalo New York
643 am EDT Mon Aug 19 2019
warm and muggy conditions will remain over the region through the
middle of the week. A weak high pressure ridge will provide mainly
dry weather outside of a few widely scattered showers and
thunderstorms today and Tuesday. A strong cold front that will pass
through the region late Wednesday will then introduce a cooler and
notably more comfortable airmass to our region for the second half
of the week.
Near term /through tonight/...
a well defined shortwave will move across the region this
morning. Regional radar shows some showers lingering east of
Rochester, and these will continue to move off to the east
A weak cold front associated with this shortwave will gradually push
across our forecast area today. The passage of this weak front
will be too early to take advantage of daytime heating, and
subsidence in the wake of the shortwave will help suppress
convection. Some mesoscale guidance develops a few showers
along a lake breeze convergence boundary south of Lake Ontario
this afternoon, but this activity will be scattered at best. All
and all, the vast majority of the daylight hours will be dry
across the region. It will also be slightly less humid today,
with dew points falling into the mid 60s behind the weak cold
front this afternoon. Highs will be within a few degrees of 80
at most locations.
Weak high pressure will build across the Great Lakes region
tonight, which will push the weak frontal boundary southward
into Pennsylvania. This will result in dry weather tonight, a
north to south clearing trend. This will provide good radiational
cooling conditions and also the risk for some fog. This will
most likely develop across the typical southern tier valleys as
long as there are ample breaks in the cloud cover. Low temperatures
will range from the mid 50s to lower 60s.
Short term /Tuesday through Wednesday night/...
Tuesday, a weak bubble of high pressure will be over the area, with
this feature pushing a frontal boundary southward across
Pennsylvania. This will allow a drier airmass with less humidity to
settle across our region to start the short-term period. As this
high advances eastward through the day, a southerly return flow will
lift the frontal boundary to our south northward as a warm front. A
few showers and thunderstorms will be possible across wny Tuesday
Shortwave timing has been key the past few days, with each wave
flaring up convection. A shortwave will approach wny late Tuesday
night and this should again Blossom showers and a few thunderstorms
late Tuesday night and towards dawn Wednesday morning. There will be
plenty of instability to start the day, with MUCAPE values of 1000
to 1500 j/kg.
As this wave passes through the region, convection will likely wane
some behind the shortwave. We will still remain very unstable and
storms are expected to again Blossom in the afternoon as lift ahead
of a sharp upper level shortwave arrives. As winds aloft begin to
increase ahead of a cold front the combination of instability
increasing towards 2000 j/kg in the mid levels and a pre frontal
trough will likely produce strong thunderstorms across the region.
Damaging winds will be the primary threat, and while cape is
impressive aloft...the higher wbz heights of around 11k feet may
limit hail. However the warmer lower levels (deeper warm cloud
depth) and precipitable waters nearing 1.75 inches will make for favorable
conditions for heavy rain.
Storms will advance towards Eastern Lake Ontario region Wednesday
evening, and likely remain on the stronger side as deep instability
Showers and thunderstorms will be swept eastward later Wednesday
night as a cold front slices across the area. This front will also
bring lowering humidity.
Long term /Thursday through Sunday/...
in the wake of a strong cold front...a much cooler and drier airmass
will continue to overspread our region Thursday and Thursday night...
with 850 mb temperatures falling to within a couple degrees either
side of +7c. The combination of lingering secondary surface troughing
and a digging upper level trough could lead to a few more isolated
to widely scattered showers on Thursday...with the cooler airmass
and loss of diurnal influences then potentially supporting a weak lake
response east and southeast of Lake Ontario Thursday night into early
Friday...with this limited by the rather dry nature of the airmass.
Otherwise...the Thursday-Friday time frame will be dry and notably
cooler as expansive surface-based ridging slowly builds southeastward
across the Great Lakes. Expect highs to mostly be in the lower half of
the 70s both days...though some of the higher terrain may see readings
confined to the upper 60s. Meanwhile lows will be mainly in the 50s...
with some upper 40s possible across interior portions of the southern
tier and north country.
After that...the axis of the aforementioned surface ridge will crest
across our region on Saturday...then will drift to the Atlantic
coastline on Sunday. This will provide our region with continued
fair dry weather both days...with diurnal airmass modification
and eventually warm air advection allowing highs to climb back into
the mid to upper 70s on Saturday...and to the upper 70s to lower 80s
Aviation /12z Monday through Friday/...
there will be some lingering showers, with patchy MVFR cigs due
to lingering low level moisture. There may be a brief period
with lower IFR cigs northeast and east of Lake Erie at kbuf and
kjhw this morning due to moisture pooling just ahead of a weak
Otherwise, today will be mainly dry, with widely scattered showers
and VFR flight conditions by this afternoon. High pressure will
build into the region tonight with mainly VFR conditions. The
only exception is where patchy radiation fog develops. This
will likely occur at kjhw, and may occur briefly at other
Wednesday...VFR with areas of IFR in thunderstorms. Some storms
may be strong with gusty winds and hail.
Thursday and Friday...mainly VFR.
winds around 15 knots at times will result in choppy conditions
today, but waves should remain below small craft criteria.
Looking further out into the middle of next week...a cold front
will cross the region on Wednesday along with more showers and
thunderstorms. In its wake...increasingly brisk northwesterly
winds will bring an increase in wave action and could eventually
require the issuance of small craft advisories for Wednesday
night and Thursday.
a cold front will move across the area on Wednesday, and
west-northwest winds will increase behind the front. The
combination of High Lake levels and increasing wave action may
bring shoreline erosion and flooding Wednesday night and Thursday.