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Area forecast discussion 
National Weather Service Buffalo New York
344 am EDT Sat Jul 4 2015

Synopsis...
a weak system will bring some rain showers and possibly a
thunderstorm to areas mainly southeast of Buffalo...Rochester...
and Watertown today. Dry weather will return this evening and last
through Monday as high pressure builds back across the region. The
next weather system is expected to arrive Tuesday or Tuesday
night.

&&

Near term /through tonight/...
at 330 am...radar shows a solid area of rain across central
Pennsylvania moving northeast. Its trajectory will clip the southeast
border of the County Warning Area with a period of rain south of a Wellsville to
Syracuse line. A significant portion of high resolution model
guidance forecasts showers develop north of this area. So far
there is little evidence of this happening on radar while the 00z
Buffalo sounding showed very dry air beneath 500mb. Expect that as
moisture continues to advect into the region a few showers will
develop northwest of this area of rain but that this will be
scattered in nature...with the Buffalo/Rochester metropolitan areas
expected to stay dry.

Steady rain showers should exit to the east by mid-morning. There
will still be a cyclonic flow aloft behind this disturbance with
limited instability likely to develop with daytime heating. High
resolution model guidance seems more realistic here...with showers
and thunderstorms forecast to develop along a convergence boundary.
This boundary will be influenced by both the shortwave aloft and
lake influences. There is fairly good agreement among NAM/rgem/hrrr
guidance that this activity will develop late morning east of Lake
Erie and Ontario. Scattered showers and thunderstorms should track
eastward during the afternoon tending not to last too long at any
given location.

High pressure will build behind the departing system tonight with
mostly clear skies outside of a a few high clouds from the departing
shortwave. This should provide good conditions for those planning to
view fireworks this evening. Temperatures will be seasonable with
overnight lows in the 50s. Some patchy fog is likely in the typical
river valleys across the southern tier.

&&

Short term /Sunday through Monday night/...
an area of high pressure over our region to start the time period
will slowly drift eastward to off the northeast coastline by
Monday night. This feature will control much of the weather
parameters this time period. Expect dry conditions Sunday and
Monday...with just a low chance for a shower late Monday night.

Sunny skies will bring sunday's temperatures into the upper 70s and
lower 80s. Warmest areas will be the valleys of the Genesee and
Allegany rivers...while coolest areas will be near the Lake Shores.
It should be the first dry Sunday across the entire County Warning Area since may
24th.

Speaking of may...temperatures Monday should be the warmest since
may as well. Temperatures at 850 hpa will warm to +16 to +18c...and
with a southerly flow ahead of a cold front we should see afternoon
highs surge into the middle to upper 80s...with a spot 90 in the
Genesee Valley. A few clouds will begin to spill across far wny
later Monday...as moisture is pulled northward between the departing
surface high and the nearing middle level shortwave trough of low
pressure from the western Great Lakes. Temperatures Monday night
within a continued light southerly flow will drop only into the 60s
with a few locations possibly remaining at only 70f for a low. There
may be a few showers well ahead of the cold front Monday night...and
will carry just low chance probability of precipitation for this light activity.

&&

Long term /Tuesday through Friday/...
on Tuesday as the parent shortwave trough tracks north of the
forecast area it will force an area of low pressure well to our
north over northern Quebec. This low however will drag a cold
front across our area with either scattered showers and
thunderstorms...or increase the chance for an mesoscale convective system tracking out of
Michigan / Midwest to move across the area. The timing of which
remains fairly uncertain at this lead time. Still temperatures
will largely remain in the low 80s on Tuesday with 850 mb
temperatures surging to around +17c ahead of the front...although
heating will be limited by increase cloud cover and chance of
showers and storms.

Weak high pressure will build into across the area Wednesday through
Friday... this will keep temperatures in the 70s to near 80 with
below normal chances of precipitation to end the work week.

Looking ahead to next weekend...forecast confidence remains below
normal... as various forecast models disagree on the timing a
shortwave that could bring increased shower/thunderstorm chances
to one of the day of the weekend. While Saturday or Sunday could
see some shower/thunderstorm activity... the weekend looks far
from a washout.

&&

Aviation /08z Saturday through Wednesday/...
an area of rain showers will pass southeast of all taf sites with just a
small chance of a shower through 15z. This close call is probably
leading guidance to be pessimistic with the 00z buf sounding
showing quite a bit of dry air beneath 15k feet. There is a small
chance for some IFR/MVFR ceilings at jhw...otherwise VFR conditions
should prevail.

Scattered showers and thunderstorms may develop along a boundary
inland of the lakes today...with a small chance these will briefly
impact Art/roc/jhw. Otherwise expect VFR conditions this
afternoon through this evening.

Outlook...
Sunday through Monday...VFR.
Tuesday and Wednesday...mainly VFR with a chance of showers and
thunderstorms.

&&

Marine...
a weak pressure gradient will remain in place across the lower Great
Lakes through the remainder of the Holiday weekend. This will
generally result in relatively light winds and minimal waves...with
local lake breeze circulations developing each afternoon.

&&

Buf watches/warnings/advisories...
New York...none.
Marine...none.

&&

$$

Synopsis...apffel
near term...apffel
short term...Thomas
long term...church/Thomas
aviation...apffel
marine...apffel/Thomas

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