Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
1036 PM EDT Thursday Jul 2 2015
high pressure will continue to build over the region tonight through
Friday with clear skies. High pressure will remain in control over
the Fourth of July weekend although an isolated shower or
thunderstorm cannot be ruled out Saturday afternoon and evening
inland from the Great Lakes. Temperatures will rise to more typical
middle Summer warmth by the weekend.
Near term /through Friday/...
high pressure will continue to build into the lower lakes overnight
with clear and moonlit skies. The clear skies and light winds will
result in good radiational cooling conditions so will hedge on the
cool side of guidance. Expect lows to range from the middle to upper
40s across the typically cooler interior locations to the lower 50s
across the lake plains.
On Friday an area of high pressure will stretch across the central
and eastern Great Lakes region. Daytime mixing up to about 850 hpa
will mix out 850 hpa temperatures around +10 to +12c down to the
surface as afternoon high temperatures in the middle to upper 70s
across lower elevations. The light synoptic scale flow and strong
differential heating will allow lake breezes to form during the
afternoon with slightly cooler temperatures along the lakeshores. Dewpoints
should remain comfortably in the upper 40s and lower 50s.
Short term /Friday night through Sunday night/...
evening update...latest global model runs and the 03/00z NAM and
02/21z sref are all showing a weak surface low tracking south of New
York Saturday morning across the middle-Atlantic region. This is in
advance of a upper trough crossing the Great Lakes. This surface low
may advect enough Atlantic moisture back over western and central
New York to trigger showers during the morning hours of the 4th with
some possibility of afternoon thunderstorms before clearing to the
east for the evening hours. This may impact daytime plans but model
timing suggests dry weather should move back in to provide clear
viewing of fireworks displays. The forecast grids are in line
although timing may need to be skewed back toward the morning hours
if later model runs continue to reflect the current thinking.
Previous discussion...it will be a quiet start to the Holiday
weekend Friday night as upper level ridging will be exiting the area
and an upper level trough over the upper Great Lakes will begin
dropping into the lower Great Lakes. This trough will remain in
place over the region on Saturday and aid in generating enough
instability to allow for the formation of scattered showers and
thunderstorms across the southern tier...Genesee Valley...and The
Finger lakes. A lack of deep moisture should limit coverage of
convection and given weak shear and instability will only run around
500 j/kg so any convective activity will be garden variety and
should be brief in nature. Areas near the Great Lakes and across the
north country should remain rain free thanks to the Lake Shadow. The
airmass in place will be just a shade cool for this time of year
with temperatures running a couple of degrees below climatological
averages thanks to the presence of the upper level trough with lows
Friday night in the 50s and highs in the middle to upper 70s Saturday.
Any shower activity will quickly dissipate after sunset Saturday
evening with the loss of diurnal heating...allowing for clear
viewing for the fireworks Saturday night. The upper level trough
will depart the region as we move into Sunday and will replaced by
upper level ridging. The increasing subsidence and warming air in
the middle-levels will keep things dry and sunny for the end of the
weekend...though weak northerly flow on the front side of the ridge
will keep temperatures in the upper 70s. The upper level ridging and
fair weather will persist through the end of the weekend with lows
Sunday night continuing to run right around normal for early
July...in the 50s inland to around 60 near the lakes.
Long term /Monday through Thursday/...
after a fine weekend and a dry start to the week on Monday...the
trend for next week will once again turn unsettled as the upper
level ridge over the northeastern U.S. Moves off the East
Coast...giving way to a low amplitude split flow upper level pattern
that will place the Great Lakes in the bullseye for systems coming
out of the Midwest and northern tier of the country. Surface high
pressure settling off the East Coast will open the way to moist
return flow off of the Atlantic across the lower Great Lakes that
will push dewpoints well into the 60s...marking a return to a
muggier...more Summer-like feel. This increased moisture will also
pave the way for development of showers and thunderstorms...subject
to the timing of the series of systems that will be impacting the
region. At this point while the models agree on the development of
this unsettled trend...timing issues abound and the best that can be
done this far out is to stick with broadbrushed chance probability of precipitation and a
warmer trend in the temperature forecast.
Aviation /03z Friday through Tuesday/...
clear skies will rule overnight as high pressure builds into the
lower Great Lakes. Some River Valley fog will bring local IFR to the
southern tier late tonight and early Friday. Otherwise clear skies
Friday morning will give way to few-scattered diurnal cumulus during the
midday and afternoon.
Saturday...mainly VFR with widely scattered showers and
thunderstorms mainly from the southern tier into The Finger
lakes with local/brief MVFR/IFR.
Sunday and Monday...VFR.
Tuesday...mainly VFR with a chance of a shower or thunderstorm
inland from the lakes.
high pressure will slowly build eastward from the central Great
Lakes region with light winds and flat wave action through the
Holiday weekend. Strong differential heating and the weak synoptic
scale flow will allow local lake breezes to develop on most days
with winds becoming onshore 5-10 knots during the afternoon.