Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
147 AM EST Fri Dec 13 2019
Valid 12Z Mon Dec 16 2019 - 12Z Fri Dec 20 2019
...Wintry weather early next week from the central Plains to the
Northeast..with heavy rain over parts of the interior Southeast...
...Pattern Overview and Guidance/Predictability Assessment with
Weather Highlights/Threats...
A low pressure system will likely bring a swath of wintry
precipitation early next week from the central Plains to the
Northeast as a shortwave trough ejecting out of the Rockies
interacts with a cold front. Models are in decent agreement on
this scenario with the GFS showing somewhat faster development and
forward speed of the low than other models. Areas of heavy rain
will also be possible across the interior Southeast before the
front moves off the East Coast Tuesday night. The air mass behind
the low will not be tremendously cold, although much of the
eastern two-thirds of the country will be colder than normal
through midweek next week.
Meanwhile, models are indicating that a Pacific cyclone will
approach the West Coast by the middle of next week. The GFS again
shows a faster forward motion with this system than other models.
More of the ensemble mean solutions were used to handle the
uncertainty. The WPC medium-range forecast grids were a consensus
of the 00Z ECMWF/EC mean with a blend of the 12Z/18Z GFS as well
as the 18Z GEFS. Precipitation ahead of the cyclone should first
reach the coast of California and the Pacific Northwest on
Wednesday, followed by slow inland progression of the
precipitation as the system is forecast the gradually weaken near
the West Coast. The higher elevations of California such as the
Sierra Nevada should see some wet snow on Wednesday into early
Thursday. The chance of snow will also be on the increase from
the Cascades to the Intermountain region late next week. In
addition, the snow along the Cascades could become heavy on Friday.
Also by late next week, models are beginning to indicate the
return of Gulf moisture across southern Texas where a coastal
front may be forming.
Kong
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