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Area forecast discussion 
National Weather Service Buffalo New York
352 PM EDT Friday Oct 24 2014

Synopsis...
high pressure over the region this evening will drift to the East
Coast by Saturday morning. A fast moving cold front will cross the
area Saturday afternoon with gusty winds and a brief period of
scattered showers...which will be most numerous across the north
country. The cold front will usher in a cooler airmass for Sunday
before a significant warming trend arrives for a few days early next
week.

&&

Near term /through Saturday/...
visible satellite imagery this afternoon showing a patch of thicker
cirrus level cloudiness crossing western New York. This should continue to
drift northeast and thin out through this evening...leaving partly
cloudy to mainly clear skies in most areas. The western edge of
lower cloud cover from the East Coast system continues to clip Lewis
County east of Lake Ontario. This too should thin out during the
evening as the coastal low pulls slowly away.

Otherwise a narrow surface ridge will remain over the lower lakes
this evening and provide a tranquil and partly cloudy to mainly
clear evening. After midnight an area of deeper low level moisture
upstream over Michigan and southwest Ontario province will spread
eastward and into western New York...with thickening cloud cover supported
by increasing low level warm advection and isentropic upglide. Lows
will be on the mild side for late October...with middle to upper 40s on
the lake plains and lower 40s in the cooler more sheltered interior
locations. The Tug Hill may drop into the upper 30s.

Saturday morning the area of isentropic upglide and enhanced low
level moisture will move east and quickly weaken...which should
allow for at least partial clearing for a few hours during the middle
morning through early afternoon.

During the afternoon a sharp middle level trough will dig towards the
Saint Lawrence valley...with an associated cold front pushing
southeast across the region. The strongest large scale ascent will
cross the north country during the afternoon with a period of strong
DPVA ahead of the shortwave and upper level divergence within the
left exit region of a 150+ knot upper level jet and area of
diffluent flow aloft. Precipitable water values rise to around 1 inch just ahead
of the front...more than ample for late fall. This should all come
together with low level convergence along the advancing cold front
to produce a 2-3 hour period of showers across the north country.
The lifted index drops to -1c to -3c depending on model of choice
across the north country...and this marginal instability combined
with strong forcing may produce a few scattered weak thunderstorms
as well. Farther southwest along the trailing cold front large scale
ascent will be much weaker...so expect showers to remain widely
scattered across the rest of the area during the middle to late
afternoon. Clouds will increase once again during the afternoon
along and behind the surface cold front as moisture becomes trapped
beneath the frontal inversion.

A brief window of 850mb temperatures around +7c just ahead of the cold
front will support above average highs...in the middle 60s at lower
elevations and upper 50s across higher terrain. Some of the warmer
spots in the Genesee Valley and northern Finger Lakes may reach the
upper 60s. It will become quite windy on Saturday...especially
northeast of Lake Erie in a corridor from the Niagara Frontier to
Rochester where BUFKIT momentum Transfer schemes suggest gusts in
the 35-40 miles per hour range during the afternoon.

&&

Short term /Saturday night through Tuesday night/...
water vapor imagery this afternoon displays two shortwaves...a
compact shortwave just to the northwest of Lake Winnipeg...and a
second more broad wave just off the northern California coastline.
These two features will be key over this upcoming timeframe.

The first shortwave will push a cold front across our region
Saturday...with the front just to the east of the County Warning Area by the
Saturday evening...the start of this time period. Aloft the
shortwave will lag behind the front with the wave still crossing
southeastward from the upper lakes to New York and New England. Any
rain showers across the southern Genesee Valley will end early
Saturday evening...though across the Eastern Lake Ontario
region...and under the upper level shortwave scattered rain showers
will linger through much of Saturday night.

Behind the cold front temperatures at 850 hpa will drop to around
-1c over Lake Ontario...and slightly warmer over Lake Erie. The
lake induced equilibrium levels will be up to 10-12k feet and there
will also be little wind shear. These factors...along with low level
convergence will aid to develop a band of lake effect rain overnight
southeast of Lake Ontario where greater ambient synoptic moisture
resides.

As lake parameters become poorer through the day on Sunday and
combined with daytime heating the band of rain off Lake Ontario will
fall apart through the daytime Sunday. South of Lake Ontario there
should be a fair amount of sunshine through the day as high pressure
builds eastward from the Midwest.

The core of the high pressure will pass across our region late
Sunday night through Monday morning. This will provide for quiet and
dry conditions. Later Monday moisture will begin to build northward
as southerly flow increases. A warm front lifting northward into the
central Great Lakes region may bring a shower far enough eastward to
brush by far western New York through the day.

Monday night the Pacific shortwave will now be just to the east of
The Rockies where it will carry and deepen an area of low pressure
from near Iowa Monday evening to the western Great Lakes by Tuesday
morning. A warm front strengthening on this deepening area of low
pressure will continue to lift northward across the central Great
Lakes...and Lake Ontario region. A few showers will be possible
Monday night across Lake Ontario and areas just to the east as the
warm front lifts northward through our region.

After this warm front passes...and with daytime mixing the first
half of Tuesday will likely feature dry conditions. However the
surface low to our west will be pushing a cold front...accompanied
by showers into western New York by the end of the day Tuesday. High
chances probability of precipitation will continue for Tuesday afternoon through the night
as the cold front and Showers Pass across the region from west to
east. Behind this cold front...and as the cold air deepens a Few
Lake effect rain showers will be possible late Tuesday night...and
mainly east of Lake Ontario on a westerly flow.

Temperatures will start around normal...to slightly cooler than
normal this time period...and then gradually warm until the cold
front passage. For Saturday night lows will generally range through
the 40s...with warmest areas under lake effect clouds southeast of Lake
Ontario. Sunday...behind the cold front will be cooler than Saturday
with highs right around normal...and that at low to middle 50s.

As high pressure drops across the region and skies clear...Sunday
night will be chilly with lows in the low to middle 30s. Again warmest
areas will likely be southeast of Lake Ontario where some linger low clouds
will reside.

Gradually warming Monday and Tuesday...such that there may be a few
70s Tuesday afternoon. With the models quicker with the cold front
and precipitation...near record warmth seems less likely now.

&&

Long term /Wednesday through Friday/...
shortwave passing north of the forecast area will push a cold front
through Tuesday night...with continued cold air advection through
the day on Wednesday. High temperatures will run about 10 to 15
degrees cooler on Wednesday than Tuesday...with middle 50s common.
Unidirectional southwesterly low-level flow behind the front...along
with continued cold air advection will support a windier day on
Wednesday.

Mainly dry conditions expected in the Post-frontal environment
Wednesday into Thursday. The exception is a chance for some lake
induced rain showers east of Lake Ontario...and south of Buffalo
toward Jamestown. Forecast soundings suggest a shallow layer of
instability...with lake induced equilibrium levels only around 5k
feet. Thus forecast confidence in intensity and coverage is
low...and have left only slight chance to chance probability of precipitation in the
forecast through the period.

The surface pressure gradient across the forecast area
will weaken Wednesday night into Thursday as the surface low near
the Hudson Bay shifts north and eastward. Winds will decrease and
shift to the west and northwest for Thursday. Another weak
disturbance will approach the area on Friday which should push
temperature slightly below normal and bring a chance for some
scattered rain showers across the forecast area.

&&

Aviation /20z Friday through Wednesday/...
VFR will prevail through this evening across the region. A patch of
thicker cirrus level clouds will drift across western New York this
afternoon...and the back edge of lower VFR level clouds from a
coastal storm will continue to cross the western Adirondacks and Tug
Hill region at times. Otherwise the rest of the area will see mainly
sky clear.

Tonight an area of deeper low level moisture upstream over Michigan
will spread east into the area after 06z. This will spread a deck of
lower clouds into the region with a mix of low end VFR and MVFR
ceilings. These low clouds will continue to drift east and break up
Saturday morning with a return to mainly VFR. During the afternoon a
cold front and potent middle level disturbance will cross the region.
This will produce a few scattered showers in most areas...with
showers more likely across the north country. A few scattered
thunderstorms are also possible across the north country. Ceilings will
initially be VFR as the showers develop...but a period of MVFR or
even IFR ceilings are expected for a few hours immediately behind the
cold front during the late afternoon. Visibility should stay mainly VFR
for most of the area with showers light and scattered in nature. The
north country may see a brief period of MVFR/IFR visibility in any heavier
and more concentrated showers.

Outlook...
Sunday...mainly VFR...except areas of MVFR east and southeast of
Lake Ontario with showers likely.
Monday...mainly VFR.
Tuesday...VFR/MVFR with a chance of showers.
Wednesday...mainly VFR except MVFR with a chance of showers east of
the lakes.

&&

Marine...
westerly winds have increased this afternoon on Lake Ontario enough
to produce marginal Small Craft Advisory conditions on the east half
of the lake. This will be short lived with winds and waves coming
back down this evening. On Lake Erie choppy conditions will persist
into this evening with winds and waves remaining just below Small
Craft Advisory criteria.

A moderately strong area of low pressure will move across northern
Ontario and Quebec on Saturday...with a trailing cold front crossing
the lower lakes during the afternoon. Southwest winds will increase
into the 20-25 knot range on both lakes ahead of the cold front...
then become west Saturday night and Sunday. Winds may increase
further to 30 knots on Lake Ontario during that time frame as cold
air deepens and promotes steep low level lapse rates and strong
mixing. This will support a period of high end Small Craft Advisory
conditions through the entire weekend. High pressure will build over
the lower lakes by Monday and bring an end to Small Craft Advisory
conditions.

&&

Buf watches/warnings/advisories...
New York...none.
Marine...Small Craft Advisory from 9 am Saturday to 8 PM EDT Sunday for
lez040-041.
Small Craft Advisory from 10 am to 8 PM EDT Saturday for
lez020.
Small Craft Advisory until 11 PM EDT this evening for
loz043>045.
Small Craft Advisory from 4 PM Saturday to 8 am EDT Monday
for loz043>045.
Small Craft Advisory from 1 PM Saturday to 5 am EDT Monday
for loz042.

&&

$$

Synopsis...Hitchcock
near term...Hitchcock
short term...Thomas
long term...church
aviation...Hitchcock
marine...Hitchcock

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