Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
143 AM EST Sun Nov 10 2019
Valid 12Z Wed Nov 13 2019 - 12Z Sun Nov 17 2019
...Record cold to slowly ease later this week...
...Pattern Overview and Guidance/Predictability Assessment...
Upper ridging will meander off the coast of California,
interrupted by troughing late Wednesday/early Thursday and then
again on Friday, with broad troughing east of the Rockies. Over
Mexico, a closed low will eventually rejoin the southern edge of
the westerlies Thursday and track across the northern Gulf of
Mexico. The models/ensembles were in good agreement overall but
with varying degrees of speed/track/evolution/interaction
differences. The 12Z GFS/ECMWF offered reasonable clustering near
their ensemble means to form the base of the initial forecast
Wed-Fri. Included much more ensemble weighting by next weekend due
to differences in western height falls into WA/OR starting late
Friday. The GEFS ensembles were quicker than earlier runs and the
ECMWF ensembles, resulting in a much more positively-tilted trough
and quicker northern stream. Favored the ECMWF ensembles for its
better consistency and closer pairing with the 12Z GFS (in a broad
sense). Along the Gulf coast, opening upper low may just miss
interacting with northern stream troughing resulting in less
surface development along the front offshore FL/SC.
...Weather Highlights/Threats...
Well below average temperatures that will likely break daily
records across a sizable area of the eastern half of the CONUS on
Wednesday will ease by the end of the week. However, highs will
remain about 10-15 degrees below average along and east of the
Mississippi into Friday and 5-10 degrees below average next
weekend. A sneaky reinforcing shot of cold Canadian air may skirt
through the Northeast Fri/Sat as another surface high moves in.
West of the Rockies (but including parts of the Front Range and
central Plains), temperatures will stay above average by about
5-10 degrees.
Once the southern upper low reaches the Gulf, its interaction with
a frontal boundary could spread rain along the I-10 corridor and
across the Florida peninsula as low pressure develops near
Florida. Next system into the Pacific Northwest will provide
focused rain/snow to coastal/mountain OR/WA Friday-Saturday then
east of the Divide Saturday-Sunday. By then, moisture will be much
more limited and precipitation amounts much lighter. Yet another
system may approach Washington late next Sunday.
Fracasso
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