Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
101 AM EST Wed Nov 11 2020
Valid 12Z Sat Nov 14 2020 - 12Z Wed Nov 18 2020
***Active weather pattern for the West and Tropical Storm Eta
affects Florida***
...Overview...
An upper level trough over the Intermountain West early Saturday,
along with a strong surface low, will then cross the Midwest
through the weekend, and reach the East Coast by Tuesday. By this
time, an upper ridge should briefly build across the Rockies and
western High Plains before the next trough and storm system
approaches from the eastern Pacific. Tropical Storm Eta is
forecast to slowly track north and move inland across the Florida
Panhandle on Saturday and then weaken.
...Guidance Evaluation/Preferences...
The deterministic guidance is in relatively good agreement through
the weekend on the synoptic scale pattern, with the ECMWF slightly
stronger with the upper trough crossing the Upper Midwest compared
to the flatter GFS. More noteworthy differences come into play
across the West Coast region by Tuesday and Wednesday with the
arrival of the next trough. The CMC is displaced to the west of
the model consensus with both the ridge axis and the incoming
trough, and the ECMWF brings height falls faster than the GFS and
the ensemble means. The WPC front/pressures forecast was
primarily derived from a ECMWF/EC blend with some GFS and CMC
through Day 5, and this is also closest to the official forecast
track of T.S. Eta. More EC mean and NAEFS mean was incorporated
for early next week to account for increasing model spread, along
with some previous WPC continuity.
...Sensible weather and hazards...
Unsettled weather is expected from northern California to
Washington state during much of this time as two additional storm
systems approach the region, with an atmospheric river event
possible late Monday and into Tuesday. This will equate to a few
inches of rainfall for the lower elevations near the Coast, and
1-3 feet of snow for the higher elevations of the Cascades and
slightly less for the northern Rockies. There will be some
moderation of the recently cold temperatures, with readings
returning closer to climatological averages for this region.
In contrast, the eastern U.S. will likely see temperatures fall
to, or slightly below, mid-November averages by early next week as
the upper trough replaces the Bermuda high. An addition round of
rain is likely ahead of the next front, followed by much drier
conditions as a large surface high builds in from the Plains.
Tropical Storm Eta is forecast to make landfall as a weaker storm
around Saturday, and then gradually dissipate as it becomes
absorbed by a frontal system. Some locally heavy rain and gusty
winds are likely where it makes landfall.
Hamrick
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