Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
214 PM EDT Tuesday may 5 2015
a weak wave of low pressure sliding along a stalled out front over
northern Pennsylvania will bring some showers to areas south of Buffalo
and Rochester through Wednesday...while locations further to the north
remain mainly dry. Following the passage of this wave...the remainder
of the work week will feature a return to dry weather and above normal
temperatures...before the next chance for precipitation arrives this
Near term /through tonight/...
as of 18z...a stalled out frontal boundary remains draped from the
Northern Ohio valley to northern Pennsylvania. To the north of this
boundary...a remnant shortwave from an earlier mesoscale convective system continues to
slide eastward along the front and is spreading increasing amounts
of middle and high cloud cover across western and north central New
York...with the leading edge of its attendant shower activity now
also trying to push into extreme far western New York. While this
should tend to weaken as it tries to push eastward into an
increasingly drier airmass the remainder of this afternoon...have
upped precipitation chances a bit across southwestern New York for the
remainder of the afternoon based on current radar trends.
The interesting part of the forecast comes for this evening and
overnight. The remnant wave from an ongoing mesoscale convective system over the Midwest
will track along the stalled frontal boundary and will start to draw
the boundary northward as it approaches. The 00z model suite
unanimously trended northward with the track of this wave and the
placement of the baroclinic zone for tonight. With confidence
increasing now that radar/satellite observations show the placement
of the mesoscale convective system...have increased the probability of precipitation to categorical across the
western southern tier and areas just south of the thruway.
Confidence is highest in this area receiving precipitation regardless
of small changes in the track of the wave...and all stand to see the
highest quantitative precipitation forecast amounts...up to an inch overnight. Confidence is lower
on how much precipitation areas from Buffalo to Rochester will
receive as there will be a sharp northern cut off to the
precipitation shield with drier northerly flow in place across the
north country and Lake Ontario. Given the northward trend in the
model guidance...have increased probability of precipitation northward into the Buffalo area
and along the thruway...with chances tapering off quickly north of
Temperatures overnight tonight will actually be fairly mild as the
baroclinic zone is almost overhead. The southern tier north to the
Niagara Frontier and into The Finger lakes region will be the
warmest given the cloud cover and warmer air trying to push
northward. Lows there will be in the upper 40s to near 50. The north
country will feel little to impact from the wave...and will actually
remain mostly clear overnight. The lack of cloud cover...light winds
and being on the cool side of the front will allow temperatures to
drop to around 40.
Short term /Wednesday through Thursday night/...
the frontal zone will sink farther south Wednesday night and wash
out...with high pressure building over the lower lakes and New
England. Skies will clear as subsidence and drying take hold behind
the weakening frontal zone. The high pressure will drift off the
eastern Seaboard Thursday and gradually advect warmer air into the
region. Temperatures will rise into the upper 70s to around 80 in
most inland locations. With the light flow a Shallow Lake breeze
should develop during the afternoon hours. Upper level ridging
should suppress isolated showers to our south and west on Thursday
afternoon...so will stay with a dry forecast for the period.
Long term /Friday through Monday/...
middle Summer heat will be the big story through much of the long term
as an expansive ridge stretching from the eastern United States into
the western Atlantic sets up a Bermuda high type pattern. Several
days of deep southwest flow across the Ohio Valley will pump very
warm and increasingly humid air into our region Friday through much
of the weekend.
Looking at the details...on Friday high pressure surface and aloft
will remain across the region. Both the GFS and European model (ecmwf) have a weak
quantitative precipitation forecast signal suggesting some convective potential inland from the
lakes...but with very warm middle levels instability will be limited
and likely capped. With this in mind have kept Friday dry. 850mb
temperatures rise to near +15c supporting highs in the lower to middle 80s away
from the lakes.
Over the weekend deeper moisture will arrive with surface dewpoints
nearing 60f...supporting greater diurnal instability. The GFS leans
a weak frontal zone into the area late Saturday through Sunday...
while the European model (ecmwf) holds this boundary farther northwest across the
central Great Lakes. The European model (ecmwf) solution seems more reasonable given
the strength of the East Coast ridge. With this in mind...any
showers and storms that do develop over the weekend will be widely
scattered and diurnal in nature. While there will be a chance of
rain in the forecast both days...the vast majority of the time
should be rain free if the frontal zone stays to our northwest.
Temperatures will remain very warm Saturday with lower to middle 80s...
maybe just a few degrees lower Sunday with more cloud cover.
By Monday the European model (ecmwf) brings the frontal zone a little closer...which
would produce better coverage of scattered showers and storms.
Aviation /18z Tuesday through Sunday/...
during the taf period...the remnant wave from an earlier mesoscale convective system will slide
eastward along a stalled out frontal boundary draped across the
Northern Ohio valley and northern PA...and will bring some showers
to areas primarily south of kbuf-kroc...the bulk of which will come
between late this afternoon and middle Wednesday morning. Meanwhile to
the north of this...conditions should remain largely dry.
In terms of flight conditions...expect the worst conditions to be
found across the southern tier...where current VFR conditions will
gradually lower to MVFR and eventually IFR tonight...before slowly
improving back to MVFR through the course of Wednesday. Further to
the north conditions should remain predominantly VFR through the
period...with cloud cover generally thinning and becoming
significantly higher in nature with increasing northward extent.
Wednesday night through Thursday night...VFR.
Friday...mainly VFR with a chance of showers southeast of Lake Erie.
Saturday through Monday...mainly VFR...with a chance of showers/
thunderstorms and attendant MVFR.
today and Wednesday...high pressure over the lower Great
Lakes will only produce light winds and negligible waves.