Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1159 AM EDT Sat Oct 19 2019
Valid 12Z Tue Oct 22 2019 - 12Z Sat Oct 26 2019
...Upper Midwest/Great Lakes storm early next week...
...Wet Southern to Eastern U.S. to include effect from remnants of
T.S. Nestor...
...Northern then Central Rockies Heavy Snow...
...Guidance/Uncertainty Assessment and Weather
Highlights/Threats...
It remains the case that an amplified and generally progressive
flow pattern will support several significant weather systems over
the lower 48 states next week. A closed upper low/trough will lift
from the MS Valley through eastern North America early to mid next
week. Deep surface cyclogenesis into the Upper Midwest/Great Lakes
will act to ramp up winds and rain with wrap-back wet snow while
forcing a lead frontal system and a return of Gulf moisture to
combine with upper support to fuel a widespread swath of heavy
rain/convection over the Eastern Seaboard. Pre-frontal
precipitation and runoff issues over the Northeast may be
significantly enhanced by interaction and merging of a developing
frontal wave over the Mid-Atlantic with the extratropical remnants
of Tropical Storm Nestor.
The pattern meanwhile reloads upstream as upper impulses/jet
energies/height falls work progressively inland over the
Northwestern U.S. early to middle of next week, and then carve out
another amplified central U.S. upper trough mid-later next week. A
series of systems/frontal passages offer a risk of Northern then
Central Rockies heavy snow. Below normal temperatures will sweep
down through the interior West/Rockies then Central U.S.
Temperatures will become 10-15 degrees below normal over the
north-central states as the post-frontal high surges southward.
Lead Gulf of Mexico moisture returning into the central Gulf Coast
and lower MS/TN Valleys followed by the Appalachians/Eastern
Seaboard should fuel widespread enhanced rain/convection with
potential for runoff issues.
The WPC medium range product suite was primarily derived from a
composite of reasonably well clustered guidance from the 06Z UTC
GFS/GEFS and the 00 UTC ECMWF/ECMWF ensemble mean, together with a
small percentage of the 00Z UKMET and CMC solutions for Days 3-5.
More of the 06Z GEFS and the 00Z EC mean together with some 00Z
NAEFS were used for Days 6-7. This guidance blend acts to
mitigate lingering timing/strength variance to maintain good WPC
system/pattern continuity.
Schichtel/Kong
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