Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
130 AM EST Tue Nov 12 2019
Valid 12Z Fri Nov 15 2019 - 12Z Tue Nov 19 2019
...Pattern Overview and Guidance/Predictability Assessment...
Upper ridging on either side of North America will favor troughing
over the CONUS with several embedded features. In the east, three
longitudinally-aligned shortwaves will progress through southern
Canada, the lower MS Valley, and the northeast Gulf on Friday. The
former will swing sharply through the Northeast with a quick shot
of reinforcing cold air while the latter will sneak out ahead of
the middle feature into the Atlantic. The shortwave initially over
MS Fri will likely slow down as heights build ahead of it and to
the north. Low pressure is forecast to develop just off the
Southeast coast and move northeastward. Western trough on Friday
will help to move the eastern system along as the flow across the
North Pacific remains progressive.
The models/ensembles were mostly in agreement though the GEFS (and
GFS) have seen a slowing trend toward the more steadfast ECMWF
ensemble mean. Blend of the 12Z GFS/ECMWF served fairly well with
the near-offshore eastern CONUS system (Canadian offshore, 18Z GFS
along the Mid-Atlantic/New England coast). In the West, one upper
low is still forecast to split off west of Baja California and
remain offshore (18Z GFS not preferred) while to the north, ECMWF
appeared too aggressive by next Tue. Blend with the 12Z GFS and
ensembles tempered this area towards Great Basin troughing given
how inconsistent the ECMWF has been.
...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 maintain near to above average temperatures by
about 5-15 degrees.
Coastal system should keep the heaviest rains offshore but this is
dependent on the track/evolution of the system. Coastal showers
(and breezy conditions) are expected per the current forecast. The
precipitation shield will move northward into New England by next
week. 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 Divide.
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