Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1232 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 activity
and runoff issues over the Northeast may be significantly enhanced
by interaction with an extratropical coastal low associated with
current Tropical Storm Nestor. Recent model solutions indicate a
trend toward curving a weakening cyclone back into New England.
The pattern meanwhile reloads upstream as upper impulses/jet
energies/height falls work progressively inland over the
Northwestern U.S. early-mid next week that 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 then into 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 18 UTC
GFS/GEFS, the 12 UTC ECMWF/ECMWF ensemble mean and the National
Blend of Models in a pattern with above normal forecast
predictability. This guidace blend acts to mitigate lingering
timing/strength variance to maintain good WPC system/pattern
continuity.
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