Area forecast discussion
National Weather Service Buffalo New York
1118 PM EDT Monday may 20 2013
Synopsis...
a southwesterly flow of warm and more humid air will continue across
the region for much of this week...while a frontal boundary also
stalls out across New York state and sets the stage for increasing
chances of showers and thunderstorms. The more unsettled conditions
will last 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 Tuesday/...
band of showers and thunderstorms is holding together across
southern Ontario and now working toward the Niagara Frontier so
have increased probability of precipitation from Buffalo north and eastward this evening
following along the lines of a mix of latest hrrr runs and radar
extrapolation. Timing continues to place thunderstorms into the
Niagara Frontier around midnight then shifting them eastward through
the early morning. 00z buf radiosonde observation shows area of elevated instability
over 1000 j/kg above 700mb which the current storms can feed off of.
Kbuf radar velocity showing no winds higher than 30 knots and with
low level inversion not expecting any severe impacts from
convection. Otherwise beforehand there is a slight chance of a pop
up shower ahead of the main line as the hrrr suggests but keep
forecast grids in line with main band of precipitation where highest
confidence lies. Temperatures will remain warm and humid. 850mb temperatures in
the middle teens and a return of blanketing cloud cover will keep
overnight low temperatures up in the lower to middle 60s across the entire
forecast area.
The upper ridge axis will be over or to the east of the forecast
area on Tuesday and will allow an influx of warmth and moisture with
dewpoints surging to the upper 60s across western New York during Tuesday
afternoon. The suppressive subsidence will be nearly absent on
Tuesday so can expect convection to develop during the afternoon
along the lake breeze boundaries and the inland terrain. Lake cooled
air will provide lake shadows within about half a county's width of
the Lake Erie and Ontario shores. Will have probability of precipitation increasing to the
likely category by the end of the day on Tuesday with the continued
influx of high Theta-E air. High temperatures on Tuesday should be in the
lower to middle 80s for most areas...lower to middle 70s expected across
the cloudier and possibly Rainier Tug Hill plateau and Eastern Lake
Ontario counties.
&&
Short term /Tuesday night through Thursday night/...
Tuesday afternoon/S convection is expected to gradually wind down
through the evening hours with the loss of diurnal heating and the
re-establishment of shortwave ridging aloft. Showers and
thunderstorms will linger longest overnight across the north country
closer to the warm frontal trough. Elsewhere once convection winds
down expect a warm and muggy night as dewpoints will remain in the
low 60s with low temperatures only dropping into the low to middle 60s
accordingly.
The warm and humid airmass will continue to be in place across the
lower Great Lakes on Wednesday with highs climbing into the 80s
and surface dewpoints running in the middle 60s. This will once again
provide a favorable environment for the development of showers and
thunderstorms across the forecast area. While lingering cloud cover
may limit instability somewhat...the presence of synoptic lift ahead
of the approaching surface front and middle-level trough combined
should still allow for the development of widespread convection by
late afternoon. With a decent kinematic field featuring great than
50kts of 0-6km of shear including a 40kt 850mb jet there is a
possibility that some of the thunderstorms could become
severe...particularly across the western southern tier where
instability should be greatest. With a relatively unidirectional
vertical wind profile the main threat with any stronger
thunderstorms should be strong winds. Large hail may also be a
possibility...once again primarily across the southern tier where the
greatest instability is expected. Additionally...precipitable waters running above
1.5 inches suggest that locally heavy rains will also be a threat.
After another warm and muggy night Thursday night...look for
temperatures to start a downward trend on Thursday as the
aforementioned cold front crosses the area. Another round of showers
will likely accompany the passage of the surface front. A few
rumbles of thunder may also be possible...however greatest
instability will have shifted to the east of the forecast area by
this point so will just carry a slight chance of thunder.
Shower activity will wind down Thursday night from west to east with
the passage of the surface cold front and upper level trough. Cold
air advection behind the front will allow temperatures to drop into
the 40s overnight...setting the stage for fairer...cooler...and drier
weather this weekend.
Long term /Friday through Sunday/...
Plenty of sunshine and seasonably cool temperatures will be the name
of the game this weekend as high pressure settles across the Great
Lakes. Friday will be the coldest day of the week as 850mb temperatures
dropping to around 0c should only yield highs topping out in the
lower 60s Friday and Saturday...nearly 10 degrees below normal.
Likewise overnight lows will run on the chilly side with readings in
the lower 40s along the lake plains while areas farther inland
across the southern tier and north country could drop into middle
30s...potentially setting the stage for a frost...particularly on
Saturday night when the surface high is prognosticated to be overhead.
A gradual rebound in temperatures is expected for the latter half of
the weekend as the coldest air associated with the upper level
trough departs the region and warmer air begins to creep north from
the Ohio Valley once again. Otherwise...expect dry weather to
continue through the end of the weekend.
&&
Long term /Friday through Monday/...
the various medium range guidance packages are in strong agreement
that generally fair and seasonably cool conditions will be in place
during this period...including the bulk of the Memorial Day weekend.
A broad based ridge will be positioned over the nations middle section
and this will leave twin troughs off the coasts of Vancouver and
eastern Quebec...where cooler than average temperatures are
expected.
A more detailed look at our region reveals that we will have some
leftover low clouds and light showers Friday morning (mainly east of
Genesee valley) in the wake of the departing frontal system...but as
low level ridging builds south across the Great Lakes...our skies
will clear out. 850 mb temperatures will drop to around 5c...so Friday will be
much cooler with afternoon temperatures generally in the lower 60s (50s
across the north country).
Expansive high pressure will build south across the region from
Canada Saturday and Sunday...with 850 mb temperatures forecast to be in the
vicinity of 4c both days. This will keep the afternoons cool and the
nights chilly with some frost possible...mainly across the southern
tier and Eastern Lake Ontario regions.
A peek ahead to Memorial Day suggests that fair dry weather will be
in place with a moderation in temperatures to near seasonal levels.
&&
Aviation /03z Tuesday through Saturday/...
expect VFR conditions to briefly deteriorate within ts around
midnight for kbuf/kiag and closer to 05z/06z for kroc and 07z/08z
for kart. Left kjhw out of ts because southern flank of storms will
remain to the north of the airfield. Some MVFR stratus is possible
here though similar to what happened last night.
The upper and middle level ridge axes to pass across the region and to
the east on Tuesday. Will have a slightly better chance of afternoon
and evening convection...along the lake breeze boundaries and over
the interior of the forecast area.
Outlook...
Tuesday through Thursday...numerous showers and thunderstorms with
associated brief MVFR/IFR...otherwise VFR.
Friday...mainly VFR with a chance of showers.
Saturday...VFR.
&&
Marine...
a line of showers and thunderstorms moving across eastern Michigan
and Lake Huron will shift east this evening and may push across the
lakes arriving near midnight and shifting east through the early
morning hours.
Otherwise...for much of this week winds will remain relatively light
and variable in direction due to a nearly stationary frontal
boundary that will remain draped across the region...as well as the
daily development of lake breezes. As a result...wave heights should
also remain minimal. Otherwise...shower and thunderstorm
chances will increase markedly for the Tuesday through Thursday time
frame. A cold frontal passage will turn winds to a northerly
direction with an increase in wave heights... especially along the
South Shore of Lake Ontario on Friday morning.
&&
Buf watches/warnings/advisories...
New York...none.
Marine...none.
&&
$$
Synopsis...jjr
near term...Smith/wch
short term...wood
long term...wood
aviation...Smith
marine...Smith
