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Area forecast discussion 
National Weather Service Buffalo New York
1104 PM EDT Sat Oct 25 2014

cooler air moving into the region behind a cold front will generate
widespread lake effect cloudiness late tonight that will persist through
Sunday along with showers east of Lake Ontario. The cool-down will
be short-lived however as a warm front will lift across the region
Monday with significantly above-average temperatures Tuesday
followed by another cold front Wednesday.


Near term /through Sunday/...
a weak surface trough beneath sharply lower 500mb heights and
associated strong middle-level lapse rates has produced a line of
showers and thunderstorms late this evening. This line is quickly
moving across The Finger lakes into south-central New York at 03z.
There have been a few isolated reports of pea-sized hail with the
stronger cells.

Overnight continued cold air advection behind this surface trough
will generate widespread lake effect cloud cover downwind of the
lakes. The shallow layer of moisture aloft /less than 10kft/ should
only result in cloudiness east of Lake Erie...however across the
north country the combination of longer Down-Lake fetch...slightly
colder air aloft...and most importantly proximity to the upper low
pressing across the Saint Lawrence valley will allow for the
development of lake effect rain showers east-southeast of the lake
later tonight. Look for temperatures to fall into the 40s tonight as
cold advection is moderated by onshore flow from the still
relatively warm lakes and subsequent cloud Cover.

Lake-induced cloudiness will characterize much of the day on Sunday
as cold air continues to advect across the region in the wake of an
upper low crossing the Saint Lawrence valley. Shortwave energy
rotating around the back side of this low will combine with lake
enhancement to produce continued shower activity across the north
country and southeast of Lake Ontario while the rest of the forecast
area will languish under cloudy skies...but dry weather. The cool
airmass and cloudy conditions will keep highs limited to the lower
50s...with higher terrain likely staying locked in the 40s.


Short term /Sunday night through Tuesday night/...
Sunday night the upper level low will now be across eastern New York
and New England. A lingering shower may remain over the north
country early...otherwise a dry night is anticipated.

High pressure...centered to our south will ridge northward over the
central Great Lakes will build towards western New York late. This
will bring clearing skies...which coupled with light winds will
allow for widespread 30s across wny. Remaining lake clouds southeast
of Lake Ontario and also across the Eastern Lake Ontario region will
likely remain most areas in the lower 40s overnight.

While this high pressure will be building across our region on
Monday with fair weather...a developing storm system across the
Central Plains will be forming. This storm system will deepen Monday
as a Pacific shortwave ejects off the central US Rocky Mountains.
This storm system will go from Kansas to just west of Chicago
Monday. A warm front extending eastward will bring some middle level
clouds across wny through the day.

This warm front will lie near Lake Ontario Monday night and a few
rain showers will be possible along the frontal boundary. A
southerly winds will also bring a mild night Monday night with
western New York in the lower 50s...while middle to upper 40s will be
found across the north country to the north of the warm front.

This area of low pressure to our west will cut northeastward through
the central Great Lakes and towards James Bay by Tuesday night. A
cold front from this area of low pressure will cross our
region...and while the timing is still wavering on the global seems likely that the front will cross later Tuesday and
Tuesday night. Outside of some rain showers early in the day along
the front...most of the area will start Tuesday dry with even some
sunny breaks. This sunshine combined with mild southerly winds will
bring the warmest day this week...with highs in the middle 60s to lower
70s across the region. Records for Tuesday include the
following...Buffalo...74/1946...Rochester...76/1984...and Watertown
75/1984. If this front is delayed enough...we may challenge some of
these records before cooler air settles into the region.

Rain showers will likely pass across the region later Tuesday and
Tuesday night. With the frontal passage later Tuesday and Tuesday
night will not mention any thunder at this time in the grids.


Long term /Wednesday through Saturday/...
in the Wednesday through Thursday time frame...surface high pressure
will progressively build eastward across the low Great Lakes
region...while aloft a broad scale trough will remain. As the air
temperatures gradually cool behind a recent cold front passage (850
hpa temperatures falling from several degrees above zero Wednesday
morning down to several degrees below zero Thursday night) light
lake effect rain showers will fall from time to time east and
southeast of the lakes. While a spotty shower/sprinkle will be
possible outside of the lake effect rain bands...the bulk of the
time should remain dry.

This cooling aloft will also maintain more clouds than sunshine
while air temperatures average around to just below normal.

Friday through Saturday the global models diverge with the
arrival/placement of the next upper level trough and pool of cold
air. The European model (ecmwf) continues to drop the core of the cold air across the
western Great Lakes and forms a cut off low over the Tennessee
Valley...while the GFS drops the cold air across the eastern Great
Lakes region. Will continue with low chance probability of precipitation for Friday/slight
chance for Saturday until certainty increases on the development of
the upper level pattern for the beginning of next weekend.


Aviation /03z Sunday through Thursday/...
a cold front has passed east of the region earlier this evening.
Gusty northwesterly winds have developed behind a trailing surface
as cold air advects across the region. Continued cold advection will
bring widespread lake effect clouds later tonight. An earlier cluster
of -tsra has moved well southeast of the taf sites as of 03z.

Guidance suggests ceilings will fall to MVFR around daybreak. East and
southeast of Lake Ontario...longer Down-Lake fetch combined with
another weaker shortwave passage will likely lead to the
redevelopment of showers across the north country later tonight.
Lake effect clouds/showers will then linger through the rest of the
forecast period as cool west-northwest flow will persist throughout
the day on Sunday.

Sunday night...MVFR ceilings thinning to scattered/few overnight across wny
but holding tough across cny.
Monday...mainly VFR.
Tuesday...VFR/MVFR with a chance of showers.
Wednesday and Thursday...mainly VFR except MVFR with a chance of showers
east of the lakes.


brisk northwesterly flow of 15 to 25 knots behind a front will persist
throughout tonight and into Sunday as it veers to the
west-northwest. The combination of this flow and cold advection will
maintain waves in the 4 to 6 foot range on Lake Erie and 6 to 8 feet
on Lake Ontario.

Winds will diminish Sunday night as high pressure moves across the
lakes...however it will likely take a few hours longer for wave
action on southeast Lake Ontario to settle...until Monday morning.
After relatively tranquil conditions on Monday...southerly winds
will freshen Monday night ahead of a cold front that will cross the
lakes Tuesday.


Buf watches/warnings/advisories...
New York...none.
Marine...Small Craft Advisory until 11 PM EDT Sunday for lez040-041.
Small Craft Advisory until 8 am EDT Monday for
Small Craft Advisory until 5 am EDT Monday for loz042.



near term...Smith/wood
short term...Thomas
long term...Thomas

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