Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 140625

Area Forecast Discussion
National Weather Service Buffalo NY
125 AM EST Tue Nov 14 2017

Isolated lake effect rain and snow showers will remain possible this
morning south and southeast of the Eastern Great Lakes...otherwise
dry conditions will prevail with cloudy skies through most of
tonight. Another weather system will bring primarily rain showers to
the region Wednesday afternoon through Thursday evening. A stronger
storm system may then bring gusty winds with rain showers Saturday
followed by much cooler temperatures and Lake Effect Snow by Sunday.


An expansive surface high centered over the Ohio Valley will slowly
shift across the eastern Great Lakes through today. Satellite
imagery shows widespread overcast skies as a wealth of moisture
remains trapped under a subsidence inversion brought on by the
surface high. The 00z KBUF sounding and regional profilers show that
this inversion is based around 5000 ft. Weak cold advection
accompanying the surface high has brought a pool of 850mb temps
around -6C over western and central NY. This is just cold enough
under northwest flow to generate some isolated lake effect rain/snow
showers south of Lake Ontario and Erie with mostly sprinkles.

As we work our way through the midday and afternoon hours later
today weak height rises and the potential for some vertical mixing
through a weakened cap could yield some sunshine but the flavor of
the day will certainly be cloudy. High temps will remain on the cool
side maxing out in the upper 30s to low 40s.


High pressure will remain across the region Tuesday night, with dry
weather and partial clearing. Expect lows in the lower 30s on the
lake plains and mid 20s across the interior Southern Tier valleys
and east of Lake Ontario.

The area of high pressure will press eastward and off the eastern
seaboard Wednesday, as warm air advection ramps up over the Ohio
Valley and Great Lakes. Strengthening southwesterly return flow
throughout the day Wednesday will aid in drawing moisture into the
region with upstream isentropic lift over the central Great Lakes
gradually spreading mid/high cloudiness into the region, followed by
increasing rain showers chances as early as Wednesday afternoon
across far western New York. A pair of mid level shortwaves will
phase across the Great Lakes on Wednesday with an attendant
strengthening surface low pushing across southern Ontario,
ultimately dragging a cold front across the forecast area Wednesday
night. Warm advection on the front side of the system will allow
temperatures to rise into the mid to upper 40s in most areas, with a
few 50 degree readings possible on the lake plains of Western New

Moisture fields steadily increase along the approaching cold front
with precipitable water values rising to near an inch. A band of
rain showers will work across the region with the cold frontal
passage. The majority of the steadier shower activity looks to exit
overnight Wednesday night or early Thursday morning, however some
scattered showers may linger during Thursday as the main upper
trough axis pushes across the region.

Lake effect/enhancement may complicate the precipitation pattern
across the area on Thursday and into Thursday night as temperatures
steadily cool aloft with 850 mb temperatures dropping to near -6C by
late Thursday afternoon. This will keep at least scattered shower
activity going southeast of the lakes into Thursday night. The
column eventually cools enough to support a change over to snow
across the higher elevations with some potential for a minor coating
of wet snow.


The long term will turn very active over the weekend as a dynamic
system crosses the Great Lakes region. This may produce strong winds
Saturday, followed by the first significant lake effect snow of the
season east of the lakes.

On Friday, surface high pressure drifting from the eastern Great
Lakes to off the eastern seaboard will maintain dry conditions, with
increasing mid/high clouds ahead of the next system.

Our attention then turns to the strong system for the first part of
the weekend. A potential vorticity analysis allows the energy to be
traced back and shows the system of interest dropping south through
the Gulf of Alaska today. This system moves into the Pacific
Northwest Thursday, then spawns lee cyclogenesis in Colorado by
early Friday. This low will take a classic Great Lakes cutter track
and move through the central Great Lakes Saturday. There remains
some timing difference between the GFS and ECMWF, with the GFS about
12 hours faster. Nonetheless, the two models have very similar
systems, surface and aloft, considering it is still five days out. A
strong and deepening surface low will cross Michigan and move to
western Quebec, with a trailing cold front surging across the
eastern Great Lakes. This will spread rain into our region Friday
night and Saturday.

This surface low track is climatologically favorable for strong
winds across our region, especially northeast of Lakes Erie and
Ontario where local funnelling off the lakes occurs. The 00/12Z
model guidance today trended weaker with the surface low and winds
aloft compared to several previous runs, but the pattern still
suggests good wind potential.

Behind the cold front, much colder air will move into the region
later Saturday night and Sunday. 850mb temps are not overly cold at
between -9/-11C, but 700mb temps of around -20C and deep synoptic
scale moisture will aid in yielding strong lake induced instability.
This may set the stage for significant lake effect snow east of the
lakes, although the details are never apparent 6 days out.


A wealth of moisture trapped beneath an inversion around 5k feet
will keep solid ceilings in place through today and into tonight.
Most cigs are VFR at 6Z but expect a lowering to MVFR toward 9-12z.
KJHW as usual is the exception, with IFR cigs this morning only
improving to MVFR after 13z or so. Additionally, some weak lake
effect showers may bring some sprinkles to KROC/KJHW. An earlier
shower at KJHW has allowed IFR VIS in BR to develop. With high
pressure slowly shifting across our region expect the lower cigs
will remain in place through tonight with only some clearing to VFR
at KART tonight. Models indicate KROC will see CIGs lower to IFR
after 00z Wednesday.


Wednesday...MVFR/IFR lifting to VFR with a chance of rain showers
Wednesday night...MVFR with rain showers likely.
Thursday and Friday...VFR/MVFR with a chance (likely east of Lake
Ontario) of rain showers, mixed or all snow Thursday night. LLWS
possible Friday night.
Saturday...Rain likely...windy.


High pressure will slowly build across the eastern Great Lakes today
resulting in continued light winds and negligible waves. A low
pressure system will pass across the lakes Wednesday and Thursday.
This will likely cause winds and waves to increase to Small Craft
Advisory thresholds Wednesday night on a southwest wind and strongly
remaining at small craft levels Thursday on a westerly wind. A few
Gale Force gusts may be possible Thursday on the eastern end of Lake

Another period of gusty winds looks to come this weekend with a
stronger storm system tracking north of the Great Lakes.





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