Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
147 AM EST Tue Feb 05 2019

Valid 12Z Fri Feb 08 2019 - 12Z Tue Feb 12 2019

...Overview...

Upper ridging will dominate the area just west of the Gulf of
Alaska as well as across the Florida Straits. This will favor
renewed troughing along the West Coast and broad WSW flow aloft
through the east.


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

18Z GFS and 12Z ECMWF clustered near their ensemble means through
most of the period, and a blend offered a good starting point.
Spread increased first over British Columbia on Saturday with the
depth/track of a forming upper low and then again by next Mon/Tue
south of the Gulf of Alaska as the upper ridging wobbles westward.
The ECMWF ensemble mean has generally been the leader in the
pattern for several days and opted to give the majority weighting
to it vs the 18Z GEFS mean, which has been subject to quite a bit
of inconsistent runs. After a fairly deep system exits through
Ontario Friday there will be a dearth of deep systems over the
CONUS, but the parade of upper height falls into/through the West
will keep that area active.


...Weather Highlights/Hazards...

Cold front in the east will push the well above average
temperatures out to sea to be replaced by near average to colder
than average readings for the weekend. From MT/High Plains to the
Upper Midwest temperatures will remain well below average on the
north side 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. Some moderating in temperatures
is likely in the east next week ahead of another weak system.

Lake-effect snows will resume Friday into Saturday as colder air
wraps around the departing surface low. Late this weekend and into
early next week, another round of potentially heavy precipitation
will spread out of the Plains into the mid-MS and TN Valleys via
the combination of  another weak impulse out of the Rockies and a
slow surge of moisture atop a warm front along the Gulf coast.
Through the West, several systems will bring generally light to
modest amounts of rain/snow to the region, especially from central
CA/Sierra northward to Oregon.


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