Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 AM EST Fri Jan 10 2020
Valid 12Z Mon Jan 13 2020 - 12Z Fri Jan 17 2020
...Weather Pattern/Hazard Highlights and Guidance/Predictability
Assessment...
A closed low/trough will shift from the Canadian Rockies eastward
across southern Canada to the Canadian Maritimes Monday-next
Friday and a cold arctic airmass coincident with lower atmospheric
high pressure will spill southward through the Northwest and the
central and eastern U.S. in the wake of passage. This offers a
threat for a swaths of snow across the U.S. northern tier of the
central and eastern U.S., albeit with mainly modest QPF.
Meanwhile underneath, an amplified mid-upper level mean trough
will periodically be reinforced with eastern Pacific energies that
dig over an unsettled western U.S. next week. WPC winter weather
outlook probabilities show a widespread snow threat over the
Northwest that may work down to lower elevations given the extent
of cold air filtration. Activity will spread down into the Sierra
and out across the north-central Great Basin/Rockies with system
progressions.
Trough energies and associated surface systems will tend to eject
east-northeastward out from the West over the central and eastern
U.S. overtop a lingering and warming/stabilizing Florida mean
ridge. There remains much uncertainty with potential cyclogenesis
scenarios in advance of the northern stream cold surge and along
lead fronts, but the pattern seems to favor the heaviest rainfall
potential next week from the lower MS Valley and Mid-South through
the Southeast overtop the shielding Florida ridge.
The latest models and ensembles are tending to converge upon a
more common solution with mid-scale systems embedded within
complex and progressive flow over the lower 48 states. This
bolsters forecast confidence a bit, but recent runs of the ECMWF
have been erratic and still offer more variance than desired.
Accordingly, the WPC medium range product suite was primarily
derived from a composite blend of the more compatable and run to
run stable 18 UTC GFS and 12 UTC ECMWF ensemble mean along with
the 00 UTC National Blend of Models. This blend maintains good WPC
forecast continuity.
Schichtel
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are 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