Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
719 am EDT sun may 24 2015
high pressure anchored off the middle Atlantic coast will produce a
beautiful day across our region today...as ample sunshine will
finally boost temperatures to above normal levels. A warm front
will then advance towards our region late tonight and Monday. This
will signal a change to warm and increasingly more humid
conditions through much of the week...with the more summery
airmass supporting the opportunity for some needed showers and
thunderstorms. The majority of the week though will be rainfree.
Near term /through tonight/...
high pressure now off the middle Atlantic coast will extend back
across the lower Great Lakes today and supply our region with
beautiful weather. Plenty of sunshine can be expected through at
least the midday hours...then high and middle level clouds will
gradually increase from west to east during the course of the
afternoon as warmer air will push our way ahead of an advancing
Unlike the past several days when we experienced cool weather...
850 mb temperatures climbing to around 12c (wrn counties) will combine with a
rising height field and ample sunshine to send our afternoon maximum
temperatures well into the 70s. Its not out of the question that parts of
the Genesee County valley could tickle 80. These temperatures will
be 10 to 15 degree f higher than those from Saturday...and 20 degree
higher than the chilly conditions of Friday.
Tonight...a weak warm front will advance towards the lower Great
Lakes from the Ohio Valley. Warmer air pushing north across this
frontal boundary will continue the process of generating abundant
cloud cover over our forecast area...with the associated lift
becoming great enough to support some showers near...and north of
Lake Ontario after midnight.
The associated warm advection will continue the trend of warmer
and warmer nights...as the Mercury tonight will only fall to
around 60 across the lake plains west of Rochester...while much of
the rest of the forecast area will experience mins in the middle to
upper 50s. This will be a far cry from the widespread frost and
freeze conditions from just two nights ago.
Short term /Monday through Wednesday/...
on Memorial Day...broad low pressure over the upper Mississippi
Valley will lift northeastward into Lake Superior...while pushing
its attendant warm frontal boundary from western New York into the
north country. The bulk of any warm frontal showers and embedded
thunderstorms should be confined to areas along and north of the
front and should thus primarily impact the north country on
Monday...while areas south of Lake Ontario should experience
generally dry weather once the boundary passes through. High temperatures
will range from the middle and upper 70s across the north country
/where the airmass will be a bit cooler and where there will be
more clouds and showers/...to the lower to middle 80s across most
areas south of Lake Ontario as warmer and more humid air pours
into the region in conjunction with the burgeoning warm sector.
The one exception to this will be immediately northeast of Lake
Erie...where a southwesterly flow off Lake Erie will keep readings
confined to the 70s.
As we get into Monday evening...any lingering warm frontal
convection across the north country will be in the process of
exiting that particular region as the warm front finishes clearing
our forecast area. Meanwhile...a very modest elongated shortwave
will be in the process of pushing into our region from the central
Great Lakes...and will probably help to trigger a new round of
scattered convection from west to east as it interacts with the
warm and humid airmass that will be in place across western and
north central New York. Given diminishing nocturnal
instability...expect that the best chances for any showers and
storms associated with this will be found across far western New
York during the evening hours...with both precipitation and thunder
chances then diminishing over time and with eastward extent during
the balance of the night. Otherwise...expect a much warmer and
humid night... with nighttime lows only falling to the middle 60s in
most places...and dewpoints hovering just a little below these
After a relative minimum in convective activity later Monday
night and early Tuesday morning...increasing daytime heating and
instability will then probably lead to a renewed opportunity for
some scattered showers and thunderstorms again Tuesday
afternoon...though without an obvious synoptic-scale trigger
present...any such activity may have to rely more on lake breeze
boundaries and orographic effects to get going initially. This
would tend to result in the typically-seen scenario where
convection initially fires to the Lee of Lake Erie and other
regions of favorable low level convergence...then spreads
northeastward through the remainder of the day along outflow
boundaries. Have attempted to reflect this in the forecast by
placing the highest chance probability of precipitation across much of the area south of
Lake Ontario and lower chance probability of precipitation further northwestward across
areas more likely to be shadowed by the lakes... though have
refrained from going lower than that just yet given that this time
frame is still a few days out. Aside from any diurnally-driven
convection...expect a very warm and humid day with highs ranging
in the middle to upper 80s away from any lake influences...with
slightly cooler temperatures found across the higher terrain.
Any diurnally-driven convection that develops Tuesday afternoon
should then tend to fade with the loss of heating Tuesday
evening...before convection probably increases again later Tuesday
night and Wednesday with the approach of a modest middle level
trough...and its attendant pre-frontal trough and trailing modest
cold front. Expect the best overall convective potential to come
during the day on Wednesday when renewed diurnal heating will lead
to greater amounts of available instability for the aforementioned
features to work with...and in turn should lead to one or more
rounds of scattered to potentially more numerous showers and
thunderstorms. Have accordingly reserved the highest overall
precipitation chances for that particular day...though have elected to
keep these confined to the high chance range for the time being.
Otherwise expect warm and humid conditions to continue...with lows
Tuesday night again struggling to fall below the middle 60s... and
highs on Wednesday reaching into the upper 70s to middle 80s...when
the warmest overall temperatures will likely be found across the Genesee
Valley and Finger Lakes.
Long term /Wednesday night through Saturday/...
as we get into the long term period...lingering showers and
storms should generally tend to diminish from west to east
Wednesday night and Thursday as the trailing cold front pushes
eastward across our region... and as a bubble of high pressure and
slightly drier/cooler air builds into our region in its wake...
with this ridge then providing our region with largely dry and
quiet weather Thursday night.
With the arrival of the slightly drier and cooler airmass...temperatures
and humidity levels should also both fall back a little for
Thursday and Thursday night. Expect dewpoints to drop back to the
more comfortable middle and upper 50s...while daytime highs retreat
to the middle 70s to lower 80s on Thursday...and nighttime lows fall
to the upper 50s and lower 60s Thursday night.
As the ridge axis slides off to our east on Friday...a
southwesterly return flow of warmer and more humid air will then
redevelop across our region...which will help boost temperatures
and dewpoints back up some 3-5 degrees or so from Thursday/S
readings. Coupled with daytime heating...the increasing warmth and
humidity will probably be enough to result in the redevelopment of
very scattered convection during Friday...for which some
broadbrush low chance probability of precipitation will again be in play.
As we head into next weekend...the GFS/European model (ecmwf) are in general
agreement on a much more significant and wave-laden cold frontal
boundary sinking in our direction from Ontario and Quebec...though
these packages /as is to be expected this far out/ still also
exhibit quite a bit of disagreement on its timing...with the GFS
considerably faster and more aggressive than its European
counterpart. While I tend to believe the latter more at this point
given the very wavy and elongated nature of the frontal boundary...
either of these scenarios would result in an increasing potential
for wet weather Friday night into Saturday...which has been
reflected in the forecast by increasing chance probability of precipitation and a trend
toward somewhat cooler temperatures.
Aviation /11z Sunday through Thursday/...
high pressure along the middle Atlantic coast will support
beautiful flying weather today. Skies will be sunny through
at least late this morning...then an Alto-cumulus deck will advance
across our region and thicken from west to east during the
midday and afternoon.
While clouds will thicken ahead of an approaching warm front
tonight...VFR conditions will persist. The lowering VFR ceilings
could be accompanied by some showers near and north of Lake
Ontario after midnight.
Monday through Thursday...mainly VFR with isolate/scattered -shra/tsra.
high pressure anchored off the middle Atlantic coast will extend
back across the lower Great Lakes through tonight...and this will
keep a relatively weak surface pressure gradient in place. The result
will be gentle to moderate winds for both lakes Erie and Ontario
with waves averaging 2 feet or less.
The only problem in the near term will once again be found on the
St Lawrence River where funneled southwest winds will freshen to
15 to 25 knots for this afternoon. A Small Craft Advisory will be
issued to cover this concern.
The surface high will remain in place off the middle Atlantic coast
through at least middle week...and this will keep a moderate
southwest flow in place across the lower Great Lakes. While
generally sub Small Craft Advisory conditions are expected...
there will be the risk for nearly daily thunderstorm activity.
Marine...Small Craft Advisory from noon today to 6 PM EDT this evening