Area forecast discussion
National Weather Service Buffalo New York
540 PM EDT sun may 19 2013
Synopsis...
a southwest flow of warm and more humid air will continue to move
into the region through the first half of the week. A frontal
boundary will also stall nearby...setting the stage for increasing
chances for several rounds of showers and thunderstorms. The
unsettled weather will continue much of the week before a strong
cold front crosses the area Thursday night with cooler and drier air
arriving Friday.
&&
Near term /through Monday/...
kbuf radar is picking up on some scattered showers and thunderstorms
developing south and east of the New York thruway at 5pm. These are
developing along lake breeze boundaries pushing inland from lakes
Erie and Ontario. While not much lightning has been detected just yet
each new scan is showing storm updrafts building and with time some
may reach levels strong enough for some lighting. Only expect this
activity to continue through sunset then end with the loss of
daytime heating. Otherwise the stabilizing effects of the lake breeze
boundaries will keep areas north and west of these boundaries dry
with a refreshing cool breeze.
East of Lake Ontario radar imagery is showing an area of showers
being supported mainly by persistent warm advection and isentropic
upglide along a slowly retreating warm frontal zone. These showers
will cross the Saint Lawrence River through late afternoon and
likely clip portions of northern Jefferson and Lewis counties before
tapering off during the evening.
Overnight into Monday morning a middle level ridge will nose north into
Michigan and the lower lakes...while northwest flow is maintained
from the Saint Lawrence valley into New England. A few weak
shortwaves will continue to traverse the northwest flow aloft...and
this combined with persistent weak warm advection and moisture
convergence along a stalled frontal boundary may touch off a few
more showers across the north country. Amounts should be of little
consequence however...and the vast majority of the time will be rain
free. Elsewhere from Oswego County westward expect a dry night with
at least partly clear skies after diurnal cumulus dissipate this
evening. The one exception may be across the higher terrain of the
southern tier where persistent south-southeast flow may bring another round of
low stratus in late tonight.
The increasing low level moisture combined with nocturnal cooling
may allow at least patchy light fog/br to develop in many areas
overnight...with the best chance of more widespread fog in the
typical southern tier valleys. Any fog that does form will burn off
by middle morning Monday.
On Monday the weak/diffuse frontal boundary will remain stalled
across northern New York. This may provide enough focus for a few more
scattered showers at times in that area. In addition...instability
will be greater on Monday than recent days as low level moisture
continues to improve. NAM/GFS both develop around 1000j/kg of cape
by afternoon inland from the lakes. This is likely overdone due to
the persistently over-estimated surface dewpoints seen in models
lately...but still may develop enough instability to pop a few
widely scattered showers and storms in the afternoon. The most
likely areas for this would be from the interior southern tier into
The Finger lakes and central New York. Onshore flow along all the
lakeshores will keep stable lake shadows apparent...with more
sunshine and much lower convective risk for the afternoon within
10-20 miles of the lakeshores.
Southwest flow aloft and building heights will boost 850mb temperatures to
around +15c in the west by afternoon...supporting highs in the lower
80s. The north country will be a little cooler with more persistent
cloud cover...expect middle 70s there. As is typically the case in
may...onshore flow will keep the lakeshores much cooler.
&&
Short term /Monday night through Wednesday night/...
Monday night any daytime convection towards the east will quickly
end with the loss of daytime heating. The upper level ridge will
begin to weaken as slight shortwaves crest the top of the
ridge...and these impulses will maintain the chance for an
overnight shower or thunderstorm.
Both Tuesday and Wednesday will be warm and humid as southerly winds
south of this weak warm front continue to advect moisture northward
across the eastern Great Lakes. Dewpoints both days are expected to
rise into the low to middle 60s...and with 850 hpa temperatures between
14 and 17c afternoon highs will be in the 70s...lower 70s across the
north country and middle to upper 70s south of Lake Ontario. Wednesday
may be a few degrees cooler due to building middle level moisture
decreasing the amount of sunshine.
This daytime heat combined with the increasing moisture will bring
an unstable environment with lifted indice's dropping into the -4 to -7c range.
SBCAPE values both days will climb into the 1000 to 1500 j/kg range
which will support an environment for thunderstorms both Tuesday and
Wednesday. The middle level lapse rates generally hold in the 6 to 7
c/km range which are not too impressive and with no strong wind
fields will hold the wording to just general thunderstorms for now.
One concern will be Tuesday when the wind field is light...less than
25 knots through 10-12k feet. This light wind field may allow for any
thunderstorms to be slow moving.
By Thursday a surface wave riding along a frontal boundary will
cross the region dragging a cold front through the County Warning Area. This again
will trigger showers and thunderstorms...with the front and falling
middle level heights providing the lift as instability will be much
weaker. 850 hpa temperatures will be a bit cooler which will allow
for cooler temperatures in the 60s. Falling dewpoints will bring an
end to the brief humid stretch.
&&
Long term /Thursday through Sunday/...
this time period will be cooler and more settled than prior days
as an upper level trough with drier air settles southward. The 12z
European model (ecmwf) is deeper and more progressive with the trough than the
corresponding 12z GFS...and the 00z gefs ensemble members.
For Friday...will have a low chance for a shower early in the day
towards the east. Otherwise will keep the remainder of Friday and
into Saturday dry as high pressure from the northern Great Lakes
pushes towards the eastern Great Lakes region. Exception will be
across the north country where if the European model (ecmwf) solution with the deeper
trough were to verify additional cloud cover and instability showers
under the cold pool will fall Saturday.
Dry weather will continue on Sunday with building heights across
the Great Lakes region. A return of warmer air at 850 hpa will bring
a return of middle 60s to lower 70s across the region.
&&
Aviation /22z Sunday through Friday/...
21z taf update includes addition of thunderstorms in the vicinity and cumulonimbus for kbuf and kjhw with
showers and thunderstorms developing to the east of kbuf and in vc
of kjhw. Some of these showers may make it to kroc but the lake
breeze should keep most activity to the south. Some areas of MVFR
ceilings across the higher terrain of the western southern tier and
Finger Lakes will slowly improve to VFR this evening..
East of Lake Ontario...scattered light showers will end early this evening
with associated MVFR ceilings north of kart improving to VFR from west
to east.
Tonight most of the lower cloud decks should erode away...although
some MVFR or even IFR stratus may re-develop across north central PA
and sneak into the higher terrain of the southern tier overnight on
persistent south-southeast flow. The increasing low level moisture may allow for
some fog development overnight...with visibility dropping to at least MVFR
in many locations with IFR more prevalent across the southern tier
valleys.
On Monday any fog will burn off by middle morning...leaving mainly VFR
for the rest of the day across lower elevations...with some MVFR
ceilings still possible in a few spots across higher terrain. A few
scattered showers may cross the north country in the morning as a
weak backdoor cold front brushes across northern New York. Additional
scattered showers and even a few thunderstorms may develop in the
afternoon across the rest of the area...mainly inland from the
stable lake shadows. Expect coverage to remain rather sparse in most
areas...and most if not all of the taf sites should remain behind
the lake breeze boundaries and in stable air.
Outlook...
Tuesday through Thursday...scattered to numerous showers and
thunderstorms with associated brief MVFR/IFR...otherwise VFR.
Friday...VFR.
&&
Marine...
quiet conditions will remain in place across the lower lakes through
much of the upcoming week. Wind directions will be variable due to
afternoon lake breezes...and also a stalled out frontal boundary
which will be nearby much of the week. Thunderstorm chances will
increase Tuesday through Thursday...and some storms may produce
brief periods of locally higher winds and waves.
&&
Buf watches/warnings/advisories...
New York...none.
Marine...none.
&&
$$
Synopsis...Hitchcock
near term...Hitchcock/Smith
short term...Thomas
long term...Thomas
aviation...Hitchcock/Smith
marine...Hitchcock
