Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 PM EST Fri Dec 13 2019
Valid 12Z Mon Dec 16 2019 - 12Z Fri Dec 20 2019
...Wintry weather threat early next week from the Ohio Valley 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 track from the Lower Mississippi Valley
on Monday into the Northeast on Tuesday. This should be a quick
moving system so lingering and significant effects are not
expected, though a swath of wintry precipitation is possible from
parts of the Ohio Valley, through the northern/interior
Mid-Atlantic, and into parts of New England. Models have come into
better agreement with the setup and track of the low, though the
GFS continues to be faster than the best consensus. Along the
attendant cold front, areas of heavy rainfall are also likely
across the interior Southeast/Tennessee Valley. SPC also
highlights a 15% probability area for severe thunderstorms Monday
across the Lower Mississippi Valley. The air mass behind the
system will not be tremendously cold, although much of the eastern
two-thirds of the country will be colder than normal through the
middle of next week.
Meanwhile, models indicate that a Pacific cyclone will approach
the West Coast by about Wednesday of next week. The GFS again
shows a faster forward motion with this system and weaker/flatter
downstream ridging across the Four Corners region. The ensemble
means also support the faster GFS, and even though the ECMWF is
notably slower/stronger with this system, it has support from the
CMC and the UKMET (through day 5), along with good run-to-run
continuity so it does not seem totally unreasonable. Given the
uncertainty though, a blend closer to the ensemble means was a
good starting point, and fit well with previous WPC continuity.
Precipitation ahead of this cyclone should first reach California
and the Pacific Northwest on Wednesday, with slow inland
progression. Snow is possible in the higher elevations, with
potentially heavy snowfall in the Cascades late next week.
Depending on how quickly the trough ejects into the Southwest,
return moisture out of the Gulf of Mexico may also begin impacting
parts of South Texas next Friday.
Santorelli/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
- Heavy precipitation across portions of California, and the
Pacific Northwest, Thu-Fri, Dec 19-Dec 20.
- Heavy precipitation across Ohio Valley, the Mid-Atlantic, and
the Northeast, Mon-Tue, Dec 16-Dec 17.
- Heavy rain across portions of the Lower Mississippi Valley and
the Southern Plains, Fri, Dec 20.
- Heavy rain across portions of the Lower Mississippi Valley, the
Southeast, and Central Appalachians, Mon-Tue, Dec 16-Dec 17.
- Heavy snow across portions of the Mid-Atlantic and Northeast,
Mon-Tue, Dec 16-Dec 17.
- Severe weather across portions of the Lower Mississippi Valley
and the Southeast, Mon, Dec 16.
- Flooding occurring or imminent across portions of the Northern
Plains.
- Flooding likely across portions of the Northern Plains.
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