Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
438 am EDT Friday Jul 25 2014
high pressure will remain in place over the Ohio Valley and provide
another day of abundant sunshine with cool morning temperatures
giving way to a warm afternoon. A weak warm front will cross the
region Saturday and produce increasing clouds later tonight and a
chance of a few showers and thunderstorms on Saturday. Unsettled
weather will then continue through early next week as several waves
of low pressure cross the Great Lakes region.
Near term /through tonight/...
clear skies and cool temperatures dominate the region early this
morning. 11-3.9 micron satellite imagery is starting to show signs
of valley fog development across the southern tier...and expect this
fog to remain until around 8-9am along the upper reaches of the
Allegheny and Genesee watersheds. Some patchy valley fog is possible
elsewhere as well...mainly near bodies of water.
High pressure will remain in place today from the Ohio Valley to the
middle Atlantic...with the ridge extending northward into the lower
lakes. An initial warm frontal segment and middle level trough will
clip the Saint Lawrence valley for a few hours this morning. This
may produce a brief period of middle/high clouds but these should stay
mainly northeast of Jefferson County. Otherwise expect some
high/thin cirrus across western New York this afternoon in advance of the
next warm frontal segment. NAM/GFS point soundings show some
lingering moisture in the 5-7k foot layer...and this may allow
scattered diurnal cumulus to develop by midday inland from the
stabilizing influence of the lakes. None of this should detract from
a mostly sunny day. 850mb temperatures of around +11c will support highs in
the middle to upper 70s at lower elevations...with lower 70s on the
Tonight high pressure begins to drift off the middle Atlantic coast
allowing south-southwest return flow to begin across the lower lakes. Middle level
warm advection will overspread western New York later tonight and allow
for increasing middle level clouds. Increasing isentropic upglide and a
weak lead middle level shortwave may even produce a few scattered light
showers or sprinkles by daybreak west of the Genesee Valley. The
increasing clouds and weak return flow will keep temperatures milder
overnight...with lows in the upper 50s to lower 60s on the lake
plains of western New York...and lower 50s in the cooler southern tier
valleys and Lewis County.
Short term /Saturday through Sunday night/...
Saturday will begin what will be a rather unsettled stretch of
weather for the northeastern US. The weekend does not look like a
total washout by any means...with some dry time built in. One
positive is that temperatures will be close to seasonal averages
with high temperatures running from the middle 70s to the lower 80s
across the region.
The details...Saturday morning a warm frontal boundary will be
located just to the west of New York state. Expect a good deal of
cloud cover to be in place...with possibly a few showers across
western areas. The warm front will be very slow to cross the
region...possibly only making it to central New York by late in the
day. That will keep the chance for showers and possibly a
thunderstorm in for the entire day...with the best chances for
measurable rainfall across western portions of New York Saturday
afternoon. High temperatures will range from the middle and upper 70s
to the lower 80s across the region. Dew point temperatures will be
on the increase as the day wears on...so it will feel a bit more
humid as well. Saturday night low pressure will pass north of the
New York and finally push the warm front east of the area early in
the night...only to be followed by cold front that will swing
through the region very late Saturday night into Sunday morning.
This will keep at least the chance for showers and thunderstorms in
the forecast. Low temperatures will remain on the warmer side with
lows ranging from the lower to upper 60s across the region.
Sunday it looks like we will be sandwiched between two low pressure
systems...one moving away from the area into New England and another
moving southeast out of the upper Great Lakes into the Ohio Valley.
There will be a boundary stretching between these two areas of low
pressure somewhere in the vicinity of New York state. Latest model
consensus shows that a good deal of the day may be dry. Severe
weather threat still looks low at this time as best shear and
instability parameters still remain to the south and southwest of
the area. This will have to monitored closely as the location of the
frontal boundary and any shift northward of the aforementioned
severe parameters could change things. High temperatures Sunday will
again range from the middle and upper 70s to around 80. Sunday night
the main shortwave aloft will drop into the base of the longwave
trough. The combination of the approaching shortwave and surface low
pressure passing just to the south of New York will mean increased
chances for showers and thunderstorms later in the night. Lows will
generally be in the lower 60s for most areas.
Long term /Monday through Thursday/...
an unsettled pattern will persist into next week with a broad 500mb
trough across the eastern states. This will keep a threat of showers
in the forecast with below average temperatures. Monday has the best
potential for showers with even thunderstorms possible as a sharp
shortwave trough and surface low which are mentioned in the short
term discussion passes across the lower Great Lakes. The extent of
showers and possible thunderstorms will depend on the exact timing
of when this system will cross New York. The 12z GFS is a bit faster
than the 12z European model (ecmwf). While most of next week will remain dry and cool
the instability brought on by the lower heights and colder air aloft
will be enough to keep a chance of diurnal showers on Tuesday
through Thursday. Lake effect rain showers may even be possible with
850mb temperatures dropping below +10c.
Cooling temperatures aloft brought on by -3sd 500mb heights will
bring below normal temperatures Monday through Thursday. Highs will
average 5 to 10 degrees below normal late July averages. High
temperatures on Tuesday will be the coolest of the next 7 days
topping out in the upper 60s to low 70s. A Pacific sourced airmass
will keep dewpoints in the 50s so overnight temperatures will only run a
few degrees below average.
Aviation /09z Friday through Tuesday/...
high pressure stretching from the Ohio Valley into the lower lakes
will continue to provide clear skies overnight and into Friday
morning outside of some middle/high clouds for a few hours around 12z
across the Saint Lawrence valley. Expect valley fog to form through
daybreak across the southern tier valleys in the typical locations
with local IFR. Kjhw has a wide dewpoint depression...so it appears
fog will not impact that terminal. The valley fog will burn off by
Today expect VFR to prevail with scattered diurnal cumulus
developing inland from the lakes...and some high/thin cirrus will
begin to spread into western New York during the afternoon. Tonight high
clouds will thicken and lower into a middle level deck across western
New York after midnight as a warm front approaches the region. Any
scattered light showers should hold off until near 12z.
Saturday through Monday...VFR much of the time with showers and
thunderstorms likely a times along with associated brief MVFR/IFR.
Tuesday...mainly VFR with a chance of showers.
southwest winds will increase into the 10-15 knot range from midday
through afternoon on Lake Erie and the east end of Lake Ontario.
This will produce some choppy conditions on both lakes for the
afternoon...but conditions are expected to remain below Small Craft
Advisory criteria. Expect more of the same through Saturday with
winds occasionally increasing into the 10-15 knot range will choppy
conditions at times.