Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
144 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 just west of the Gulf of Alaska will
maintain the general northerly flow aloft through the Pacific
Northwest. The models/ensembles were in reasonable agreement on
the 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. This included the 12Z ECMWF with some agreement by the 12Z
GFS later in the period.


...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 will mostly see below average temperatures due to the
persistent troughing with slightly below average temperatures in
the Upper Midwest. Another brief surge of above average
temperatures 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
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. 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. Back to the east, ensembles
continue to focus precipitation on TN/KY next week.


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