Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1100 AM EST Wed Feb 06 2019

Valid 12Z Sat Feb 09 2019 - 12Z Wed Feb 13 2019

...Overview and Guidance/Predictability Assessment and
Preferences...

Western troughing will slowly translate eastward by the middle of
next week as ridging over Florida slips toward the Greater
Antilles. Upper ridging beginning just west of the Gulf of Alaska
and transitioning slowly eastward will maintain the general
northerly flow aloft through the Pacific Northwest. The GFS and EC
models/ensembles were in reasonable agreement on the general
longwave pattern but continue to have trouble resolving the split
flow around the upper high upstream (underneath the ridge and to
its northwest through western Canada). That pattern orientation
yields below average confidence in system track/timing regardless
of the apparent model agreement. Thus, a blend of the
closest-clustering members to an acceptable evolution--mostly near
the well-performing ECMWF ensemble mean--drove the forecast again
today.The 00Z GEFS mean and 00Z and 06Z GFS were utilized as well.
The 00Z UKMET evolved the upper low in the eastern Pacific
differently than other models, splitting the low and sending
energy eastward more quickly. This was much like yesterday's 00Z
ECMWF, which was not preferred, and models have trended away from
that solution. That and the 00Z CMC were excluded from the model
preference for day 4 and beyond.


...Weather Highlights/Hazards...

Much below average temperatures will remain anchored over the
Northern High Plains throughout the medium range period, north of
an arctic front that will linger near the Divide. The rest of the
West is forecast to see below average temperatures due to the
persistent troughing with slightly below average temperatures in
the Upper Midwest. Another surge of above average temperatures in
the Southeast to Ohio Valley will precede a frontal system Tue/Wed
as a surface low lifts toward the Great Lakes/Northeast.

Late this weekend and into early next week, another round of
potentially heavy precipitation will spread into the Lower to
Mid-Mississippi and Tennessee Valleys via the combination of a
lead weak impulse out of the Rockies and a slow surge of moisture
atop a warm front along the Gulf Coast. As a low pressure system
strengthens in the Ohio Valley during the middle of next week,
precipitation is expected to continue for the Tennessee and Ohio
Valleys. Wintry precipitation will be possible for the north
central and northeastern U.S. where temperatures will be colder.
Through the West, low pressure systems will bring several rounds
of light to moderate valley rain/mountain snow to the region,
especially from central CA/Sierra northward to Oregon.


Tate/Fracasso


WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation and winter weather outlook
probabilities 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