Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 AM EST Tue Nov 06 2018

Valid 12Z Fri Nov 09 2018 - 12Z Tue Nov 13 2018

...Guidance/Predictability Assessment and Weather
Highlights/Threats...

Latest GFS/ECMWF and GEFS/ECMWF ensembles are now much better
clustered at medium range time scales, bolstering forecast
confidence. A composite blend solution is suggested.

Amplified/dynamic mid-upper level trough passage Friday/Saturday
from the north-central to northeastern U.S. will support lead
surface low and frontal system strengthening and progression. Gulf
and Atlantic moisture feeds will favor moderate rains from the
western Gulf Coast northeastward through the
Appalachians/Southeast and up the Eastern Seaboard. Cooling
post-system temps will meanwhile favor wrapback and Great Lake
effect snows that spread into the interior Northeast as leading
cooled high pressure erodes. Precipitation may then be enhanced
into Saturday with main low deepening/passage and triple point
coastal low organization. Lingering showers will be maintained
into next week back over Florida and the western Gulf Coast with
trailing frontal slowdown.

Deep storm tracks into the northeast Pacific/Gulf of Alaksa should
maintain an amplified downstream ridge position along/offshore
western North America. This will allow for further downstream
mid-upper level trough re-development. In this flow moisture will
be more limited in a wake of the lead system, but clipper low
track and favorable dynamics should squeeze out a swath of
organized snow in cooled air from the Upper Midwest/Great Lakes
into the Northeast from the weekend into early next week.

Upstream, Pacific trough energy and height falls may start to work
into the Northwest in about a week as the lead/amplified ridge
aloft gradually/finally shifts inland. This may support an
increased chance for precipitation including some modest elevation
snows.

Schichtel


WPC medium range 500 mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indexes are found at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml