Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
205 PM EST Mon Jan 20 2020
Valid 12Z Thu Jan 23 2020 - 12Z Mon Jan 27 2020
...Overview...
Scattered to widespread precipitation is expected to spread from
the Lower Mississippi Valley to areas north and east through the
weekend and into early next week. There may be periods of locally
heavy rain, particularly near portions of the central and eastern
Gulf Coast and possibly into the higher terrain of Southern
Appalachian region. A swath of wintry precipitation may fall north
of the surface low pressure system- across the Midwest, Ohio
Valley, Central/Northern Appalachians and the Northeast.
In the Pacific Northwest, several frontal systems will bring
periods of wet weather to much of Washington/Oregon to start then
into northern California by the weekend. Overall, milder
temperatures will prevail over most of the CONUS during the
period.
...Guidance/Predictability Assessment...
Model guidance remained in fair agreement with the system crossing
the central and eastern states, however continued to having spread
in how the mid/upper level features evolve. This caused noticeable
differences in amplitude, timing and where max QPF will focus. A
combination of the 00Z ECWMF, 00/06Z GFS, 00Z CMC and the 00Z
EC/GEFS means provided a decent starting point. This combo
suggested that an area of concentrated precipitation will likely
occur near the Gulf Coast and along parts of the Appalachian
spine. Moderate, possible locally heavy rain, may increase the
threat for flash flooding across the Gulf states/Southeast this
weekend. With the progressive nature of this system, the risk may
remain Marginal. Off the West Coast, with continued timing
differences in the guidance with successive systems, a consensus
approach was prudent there as well.
...Weather/Hazard Highlights...
A vast portion of the country will have above average temperatures
through early next week; ranging from about 5 degrees above
seasonal average near the Gulf of Mexico to 10 to 25 above along
the U.S and Canadian International border. Daytime highs may stay
below average where the rain associated with the southern system
is most prevalent.
Intermittent periods of precipitation can be expected across the
Northwest and parts of California and the Interior as several
systems make through way onshore. Rainfall will expand out of
Texas to points eastward/northeastward as the system organizes
across the lower Mississippi Valley. Moisture-rich air will
transport northward from the Gulf of Mexico and will continue to
fuel modest precipitation up the eastern Seaboard. The system will
likely have some wintry weather on its northern side from the
Central Plains to the Great Lakes and Northeast but with uncertain
amounts and a marginal thermal environment.
Campbell
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