Area forecast discussion
National Weather Service Buffalo New York
352 PM EDT Tuesday may 21 2013
Synopsis...
a southwest flow of warm and humid air will continue through most of
the week. There will be a chance for scattered showers and
thunderstorms through Thursday...before a cold front crosses the
area and Ushers in cooler and drier weather for the end of the week
and the Memorial Day weekend.
&&
Near term /through Wednesday/...
very unstable air (ml convective available potential energy averaging 1500-2000 j/kg and Li/S down
to -8) and moderate effective bulk shear in the vicinity of Lake
Ontario will set the stage for the possibility of more severe
thunderstorms during the afternoon and evening. As a result...severe
thunderstorms watch 203 has been issued for all of the County Warning Area south of
Jefferson and Lewis counties through 01z.
Will be keeping an eye on the potential for more thunderstorms as
mesoscale boundaries interact with the very unstable air that is in
place. The front that is stalled over Lake Ontario and weak lake
breezes will serve as the the primary initiators for convection.
The chance for convection will be lower across the north country
where the air will be more stable north of the stalled front.
Expect the convection to diminish with the loss of daytime heating
this evening. The possible exception to this general trend will be
east of Lake Ontario where the remnants of the ongoing mesoscale convective system...located
just east of Georgian Bay...may impact the north country country
through early tonight.
For Wednesday...the main focus will shift to the surface low and
trailing cold front that will be heading east toward the lower Great
Lakes. As this system approaches western New York during the
afternoon...will indicate increasing probability of precipitation for showers and
thunderstorms. Regarding the potential for severe weather...the
latest stability indicies suggest that the atmosphere will not be as
unstable as it is this afternoon...although modest shear profiles
could still result in some organized convection.
Warm and rather humid conditions will continue to tonight with
temperatures expected to range through the 60s. Temperatures on
Wednesday will warm into the upper 70s to middle 80s.
&&
Short term /Wednesday night through Friday/...
western and north-central New York will continue to be under the
influence of a warm...moist...and unsettled airmass Wednesday night
as the area will be located downstream of a deep upper level trough
centered over the central Great Lakes with a corresponding broad
surface low/trough lifting northeast across the lower Great Lakes
and Saint Lawrence valley. Afternoon thunderstorm activity should
gradually wind down during the evening hours with the loss of
daytime instability...though there should be enough lingering
instability to keep at least a chance of thunder in through the
evening hours. After that expect another warm and muggy night with
lows only dropping into the low to middle 60s and at least scattered
showers continuing through the night across the forecast area thanks
to the continued abundance of moisture and synoptic lift.
The surface trough will slide across western New York Thursday
bringing yet more shower activity and plenty of additional rainfall
to the area. An influx of cooler...more stable air into the region
should preclude the formation of thunderstorms however as the area
of greatest instability will be located well to the east...across
the Hudson Valley...by this point. Between the abundant cloud cover
and rainfall associated with the trough and 850mb temperatures that will
fall from +12c to +8c through the day...look for highs to top out in
the lower 70s...with middle 70s in The Finger lakes...ahead of a
steeper drop in temperatures that will occur Thursday night as the
axis of the upper level trough and a surface cold front drop across
the lower Great Lakes.
We can expect one more batch of heavier showers associated with the
strong height falls aloft and the surface front to bring one more
soaking rain Thursday night into Friday morning before much cooler
and drier air pushes into the region behind the front. With 850 mb
temperatures dropping to 0c on Friday...expect a much cooler day with
clearing skies and highs only in the 50s as dry northwesterly flow
takes hold across the region paving the way for chilly temperatures
Friday night and a cool and dry weekend.
&&
Long term /Friday night through Tuesday/...
seasonably cool and dry weather will prevail through the weekend and
into Monday courtesy of high pressure that will be meandering across
the Great Lakes through the forecast period. While it will be quite
chilly both Friday and Saturday nights with temperatures dropping
into the low 40s along the lake plains and into the middle-30s across
the colder spots of the southern tier...at this point am not
thinking that frost will be as much of a concern as there should be
enough of a northwesterly breeze through the night thanks to the
pressure gradient between the high pressure building in from the
west and a deepening low over northern New England. Daytime highs
will increase slightly each day of the period as the strong ridge
over the central U.S. Nudges eastward and heights gradually rise
across the lower Great Lakes with highs in the low 60s Saturday
climbing back to the upper 60s...near normal...by Monday.
&&
Aviation /20z Tuesday through Sunday/...
scattered thunderstorms will continue to impact the area for the
rest of the afternoon and evening as very unstable air interacts
with weak lake breeze boundaries and a front that is stalled over
Lake Ontario. While mainly VFR conditions will prevail...passing
thunderstorms could briefly lower visibilities to MVFR/IFR. Damaging winds
and large hail may accompany some of the thunderstorms that develop
this afternoon and early evening.
Tonight...additional convection passing north of Lake Ontario may
impact areas of east of Lake Ontario. Otherwise...somewhat quieter
weather will return for the overnight hours.
Low pressure heading east toward the lower lakes will bring
increasing chances for showers and thunderstorms Wednesday
afternoon. Once again...expect mainly VFR conditions to
prevail...with brief periods of MVFR in the vicinity of
thunderstorms.
Outlook...
Thursday...scattered to numerous showers and thunderstorms with
associated MVFR/IFR...otherwise VFR. Friday...mainly VFR with a
chance of showers.
Saturday and Sunday...VFR.
&&
Marine...
relatively light and variable winds will prevail through tonight
with a weak front draped over Lake Ontario. Southwest winds will
pick up a bit on Wednesday afternoon as an area of low pressure and
its trailing cold front approach western New York late in the day.
After the front crosses western and central New York Wednesday
night...the winds will veer to the northwest on Thursday.
Small craft advisories may be needed late Thursday night into Friday
morning as north to northwest winds pick up behind the departing
front.
&&
Buf watches/warnings/advisories...
New York...none.
Marine...none.
&&
$$
Synopsis...tjp
near term...tjp
short term...wood
long term...wood
aviation...tjp
marine...tjp
