Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Buffalo New York
1057 PM EDT Mon may 22 2017
a weak ridge of high pressure will bring dry weather Tuesday through
most of Wednesday. Low pressure will then bring more rain to the
region Wednesday night and Thursday.
Near term /through Tuesday/...
a weak ridge of high pressure surface and aloft will build over the
lower Great Lakes tonight. Subsidence and drying associated with
this high will continue to support clearing this evening, with the
Eastern Lake Ontario region the last area to clear overnight. The
clearing skies and a fairly cool airmass will allow for some
radiational cooling overnight. Expect lows in the upper 40s to around
50 on the lake plains, with low to mid 40s in the cooler sections of
the interior southern tier and Lewis County.
On Tuesday the weak surface ridge will remain in place from the
upper Ohio Valley to New England. Meanwhile warm advection and a
weak mid level shortwave will move northeast across southern
Ontario. This feature will have little direct impact on our area,
with any scattered showers remaining north of the Canadian border.
It will bring some increase in moisture and cloud cover, with both
mid level clouds and diurnal cumulus developing across the region.
Stable lake shadows will allow more sunshine northeast of lakes Erie
and Ontario. Temperatures will rebound, with highs in the lower to
mid 70s away from lake influences. Weak synoptic scale flow and
strong differential heating will allow local lake breezes to develop
with winds becoming onshore along all the shorelines in the
afternoon, keeping temperatures cooler within a few miles of the
Short term /Tuesday night through Thursday night/...
bubble of high pressure becoming centered across New England will
maintain dry weather across the area through the first half of
Wednesday. Overnight lows Tuesday night will fall back into the
upper 40s to lower 50s.
High pressure will exit the region Wednesday as a deepening surface
low slowly tracks into the Ohio Valley. Model tracks differ
slightly, but most of the guidance eventually tracks this low across
Ohio Wednesday night and across Lake Erie on Thursday. Increasing
moisture transport and lift on the front side of the approaching low
will eventually allow precipiation to Blossom across the area. Onset
time may be slowed a bit from continuity based on slower track of
approaching surface low. Warm air advection and slower timing of
precipitation onset should allow high temperatures Wednesday to
reach the lower to mid 70s.
Does look like there will be at least a solid 6 to 12 hour period of
fairly steady rain starting late Wednesday in the far west and
filling in across the rest of the area through Thursday. The steady
rain should taper to more showery weather by Thursday night as the
surface low starts to shift east of the area.
Long term /Friday through Monday/...
our region will be under the influence of a progressive...northern
branch of a split flow during this period. While this will allow for
fairly frequent shower activity...a closed off Gomex will keep
rainfall amounts to a minimum. This pattern will also keep
temperatures from straying too far from normal...but on average...
they will tend to run a few degrees above typical late may values.
Breaking this down on a day to day basis...
A stacked storm system over eastern New York Friday morning will
exit across New England during the afternoon and evening. This will
keep some showers in place over our region...particularly east of
Lake Ontario where pops will be raised to likely. Temperatures on
Friday will climb into the 60s.
Ridging will build across the lower Great Lakes late Friday night
and Saturday. While the models are not convinced that dry weather
will prevail during this time frame...am fairly confident that the
aforementioned ridging and lack of mid level moisture will translate
into fair dry conditions. This should also help Saturday afternoon
temperatures climb into the 70s across most of the western counties.
As the ridge pushes east of our region Sunday and Monday...the next
longwave trough will dig across the upper portions of the
Mississippi Valley and Great Lakes region. This will result in
deteriorating conditions...particularly late Sunday into Monday. In
other words...as it stands now we should be able to get through most
of Sunday before the skies 'open' again. Given the inconsistencies
between the medium range ensembles though...confidence is lower than
Aviation /03z Tuesday through Saturday/...
a weak ridge of high pressure will then build over the lower Great
Lakes region tonight and Tuesday with VFR prevailing. Weak warm
advection and diurnal cumulus will bring some increase in cloud
cover on Tuesday, with ceilings remaining VFR.
Tuesday night and Wednesday...mainly VFR.
Wednesday night...VFR/MVFR with a chance of showers.
Thursday...VFR/MVFR with showers likely.
Friday...VFR/MVFR with a chance of showers.
weak high pressure will build over the lower Great Lakes tonight
through Wednesday, providing a period of light winds and flat wave
action through the middle of the week.