Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
313 AM EDT Tue Oct 22 2019
Valid 12Z Fri Oct 25 2019 - 12Z Tue Oct 29 2019
...Guidance/Uncertainty Assessment and Weather
Highlights/Threats...
Models and ensembles continue to show quite varied medium range
solutions that mainly stem from the extent of short range
shortwave digging down through the w-central U.S. and subsequent
southern stream flow separation. Forecast confidence is not
stellar.
Recent ECMWF and to a slighly lesser extent ECMWF ensemble mean
and Canadian/Canadian ensembles and to some extent the UKMET
continue to show max digging within the full envelope of
solutions. This leads to the most separated southern stream and
most westward/amplified closed low development and slowest/wettest
subsequent northeastward system track over the central then
eastern U.S. at medium range time scales as a new upstream upper
trough amplifies sharply back over the West and upper ridging
builds over the Southeast. Recent GFS and to a lesser extent GEFS
runs instead show the least short range digging over the West that
subsequently offers much less downstream southern stream
separation, no closed low development, and way more progressive
and eastward flow over the central to eastern U.S. that offers a
significantly less heavy rainfall threat.
Still suspect that the sharp upper ridge amplitude building into
the West coast over the next couple of days and sufficient
wavelength spacing from subsequent upstream upper trough approach
from the Pacific should favor a solution well on the more
amplified and southern stream/closed low separated side of the
aforementioned full envelope of guidance solutions. Given the
GFS/GEFS have not trended significantly in that direction with the
latest 00 UTC runs, opted to not jump all the way to the ECMWF at
this point given lingering uncertainty. However, suggest
preference of the still stormy ECMWF ensemble mean and the
Canadian/Canadian ensemble mean that were primarily used as a
starting point for the WPC medium range product suite. This
solution offers a threat of widespread heavy rainfall/convection
centered over the South Fri into the weekend from the main lead
system and substantial cooling upstream over the West/Rockies to
include a threat of heavy mountain snows to occur by early next
week upper trough amplification.
Schichtel
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