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Area forecast discussion 
National Weather Service Buffalo New York
400 PM EDT sun may 24 2015

a warm front will lift north across the Great Lakes
tonight...bringing a few high clouds and a chance of showers to the
Saint Lawrence valley. Behind the warm front...look for very warm
and generally dry conditions for the Memorial Day Holiday. With high
pressure remaining anchored off the East Coast...warm and moist
return flow will keep Summer-like temperatures and a chance of
showers and thunderstorms in the forecast through much of the
upcoming week.


Near term /through Monday/...
sunshine is becoming more filtered across western and north-central
New York this afternoon as high clouds are starting to stream across
the area in association with warm advection aloft ahead of an
approaching surface warm front. The front will lift north across the
Great Lakes tonight...however as the low level jet and thus the bulk
of the isentropic uplift will be displaced well to our west across
eastern Ontario and the Ottawa Valley...expect it to remain dry
across the forecast area tonight with only a slight chance of
showers across the Saint Lawrence valley late. The warm air surging
north across the region will result in a very mild night with lows
in the middle to upper 50s.

The Memorial Day will usher in a return to Summer as the area will
located firmly within the warm sector of a surface/mid-level low
over the western Great Lakes. Warm air aloft will largely stymie any
convection across much of the forecast area...though with increasing
dewpoints on return flow...cannot rule out a few showers firing
along the Lake Erie lake breeze in the afternoon. The only other
area where we may see a chance of showers and possibly a
thunderstorm or two will be across the north country...closer to the
warm frontal boundary. The aforementioned southerly return flow will
boost temperatures well into the 80s...with readings hitting the middle
to upper 80s along and north of the thruway where southerly
downsloping will help bump readings up a couple of degrees. The only
areas that may remain in the 70s will be immediately adjacent to the
cooler lakes and the north country...where a synoptically enhanced
lake breeze and cloudiness associated with the warm front will keep
temperatures down slightly.


Short term /Monday night through Wednesday/...
Monday night a surface warm front will finish its northward exit
through the County Warning Area ushering in warmer...and more humid air. A few
showers and thunderstorms will likely linger east of Lake Ontario
Monday evening in the vicinity of the warm front. Additionally
showers and thunderstorms over the Ohio Valley Monday
afternoon...forming to the Lee of a building upper level ridge may
sneak into western New York during the evening hours. With the loss
of daytime heating afternoon and evening convection will diminish
through the middle and late evening hours. It will remain warm
overnight with lows only in the low to middle 60s.

Tuesday will have a taste of Summer to the day as a large upper
level ridge of high pressure builds along the eastern coastline.
Initially the lower atmosphere will be capped...with sunshine and
clouds around. With 850 hpa temperatures around +15c surface heating
through the day will bring sbcapes 500 to 1000 j/kg. This
instability...and the weakening of the cap should allow for
afternoon showers and thunderstorms to Blossom. There should be
enough wind aloft...0-6km shear of 30 knots to allow these storms to
grow...with a few possible inland strong storms in the afternoon.

A weak wave aloft will pass through the central Great Lakes/Lake
Erie region Tuesday night and early Wednesday which will maintain
chances for showers and thunderstorms Tuesday night. With no change
in airmass the air temperatures Tuesday night will be similar to the
prior night with lows in the low to middle 60s.

On Wednesday a weak surface front accompanying upper level shortwave
trough will slide across the region. Will continue with high chance
probability of precipitation...and even some likely probability of precipitation as more favorable lifting will be
found this day in addition to favorable instability and moisture.
Additional cloud cover on Wednesday will bring afternoon
temperatures a few degrees cooler with temperatures in the middle 70s
to lower 80s.


Long term /Wednesday night through Sunday/...
the strong ridge of
high pressure over the east coastline early week...will now be off
the Atlantic coastline to start this time period. This will allow
subtle shortwaves to track closer to the eastern Great Lakes region
and maintain low chances for showers and thunderstorms. Greatest
chances Thursday and Friday will be inland and along lake breezes
where afternoon instability aided by lift from lake breeze
circulation should trigger a few showers and thunderstorms. With the
upper level ridge now eastward we should not be as capped as earlier
in the week...allowing more favorable conditions for storms to brew.
Will maintain low chances probability of precipitation in the grids...though much of the
time should be rain free.

As we head towards the weekend 12z global models indicate a cold
front with more widespread showers and thunderstorms will pass
through the region. Differences are that the GFS is a bit
faster...while the European model (ecmwf) with several convective surface waves on
the front is slower. Will have high chances probability of precipitation for both weekend
days to account for the uncertainty...but none the less this front
represents the greatest chances for showers and thunderstorms this
time period.

Temperatures will continue to average above normal. Warmest period
will likely be Friday/Saturday ahead of the cold front where upper
70s to middle 80s will be found across the region. It will turn briefly
cooler behind the front to close out the weekend.


Aviation /20z Sunday through Friday/...
high clouds are increasing in coverage across the forecast area this
afternoon as a warm front approaches the region. Clouds will thicken
and lower into a middle-level deck around 10kft later this evening as
the front lifts north across the lower Great Lakes tonight. The bulk
of the convergence and lift associated with the front will remain
focused well to the north across Ontario/Quebec...suggesting that
the bulk of any convection should occur across Canada late tonight
and into Monday. That said the front will be draped close enough to
the area to warrant at least a chance of showers/isolated
thunderstorms across the Saint Lawrence valley on Monday.

Otherwise...the rest of the forecast area will remain dry through
tonight. Increasing southerly return flow behind the front may pump
up surface dewpoints enough to trigger a few showers along Lake Erie
lake breeze Monday afternoon...however warm temperatures aloft in
should largely suppress convection across the forecast area with VFR
conditions prevailing through the rest of the period.

Monday through Thursday...mainly VFR with isolate/scattered -shra/tsra.


a Small Craft Advisory remains in effect for the Saint Lawrence
River where prevailing southwesterly flow is being enhanced by the
lake breeze. As with yesterday...winds should diminish around

Otherwise...high pressure docked 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 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 along with a light
chop...particularly on the east ends of the lakes.


Buf watches/warnings/advisories...
New York...none.
Marine...Small Craft Advisory until 6 PM EDT this evening for slz022-



near term...wood
short term...Thomas
long term...Thomas

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