Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1047 AM EST Wed Nov 13 2019
Valid 12Z Sat Nov 16 2019 - 12Z Wed Nov 20 2019
...Pattern Overview and Guidance/Predictability Assessment...
Upper pattern will transition toward western troughing and eastern
quasi-zonal flow in about a week, after two successive systems
lift northeastward along the East Coast. In the West, upper
ridging will weaken as it slides eastward atop a closed upper low
moving away from Baja California. This will pave the way for a
Pacific shortwave to dig through interior California as downstream
heights rise in response.
Off the Southeast coast, the models have come into better
agreement with mostly some timing differences as the surface low
looms offshore. Another system upstream will act to kick this lead
shortwave along by the end of the weekend, but reinforce the
surface boundary along the Gulf Stream. This may develop another
low off the NC coast by early next week, though models continue to
struggle with intensity/depth of this next system. In the West,
the leading front into Washington will weaken in favor of a
stronger shortwave on its heels. The ECMWF continues to be the
most aggressive with this feature digging it farther southwest
than the other guidance. GFS is better in line with the ensembles
but given how much upstream ridging is forecast to build into the
Gulf of Alaska, the ECMWF solution cannot be ruled out completely.
This would carry a cold front through the Great Basin into the
Four Corners region by next Wednesday.
Across the board, the WPC blend uses the ECMWF and prior 2 runs of
the GFS, along with previous WPC continuity and ensemble mean
guidance (ECENS and GEFS). Due to greater differences as noted
above later in the period, both in the East and the West, more
ensemble mean weighting was used by the middle of next week.
...Weather Highlights/Threats...
Below average temperatures in the East will slowly moderate back
toward more typical mid-November values by early next week. Much
of the West will have temperatures above normal by 5-15 degrees
through this weekend, cooling early next week with the arrival of
the next upper trough.
The system off the Southeast/Mid-Atlantic coast should keep the
heaviest rains offshore but should be close enough to produce at
least showers along the I-95 corridor. Heavier rain is possible
right along the coast of North Carolina. The strong pressure
gradient between the low and the sfc high over New England will
lead to windy conditions along the coast. The precipitation shield
will move northward into New England early next week where
temperatures may be cold enough for some snow in higher
elevations.
Several systems out of the Pacific will maintain a rather wet
period for at least coastal Washington/Oregon and the Cascades,
with less rain/snow along and just west of the Continental Divide.
With increased troughing toward the Southwest next week, some
light precipitation will be possible late Tue into Wed though this
depends heavily on the evolution of the Western U.S. trough
digging southward next week.
Santorelli/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