Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1200 PM EDT Fri Oct 18 2019
Valid 12Z Mon Oct 21 2019 - 12Z Fri Oct 25 2019
...Upper Midwest/Great Lakes Storm...
...Potential Tropical Cyclone Sixteen to threaten the Northeast...
...Heavy rain and mountain snow from the Cascades to the
North-Central Rockies...
...Guidance/Uncertainty Assessment and Weather
Highlights/Threats...
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 Plains 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 across
the east-central states. Activity over the Northeast may also be
significantly enhanced by interaction/merging with a Mid-Atlantic
frontal wave with the current Potential Tropical Cyclone Sixteen.
Recent model solutions indicate a trend toward curving a weakening
cyclone back into New England by next Tuesday.
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 heavy rain and
mountain snow from the Cascades to North-Central Rockies. 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 may
fuel enhanced rain/convection, with modest precipitation inland
over the east-central states including the possibility of
wrap-around snows for a cooling Upper Midwest by late next week.
The WPC medium range product suite was primarily derived from a
composite blend of reasonably well-clustered guidance from the 06Z
GFS/00Z ECMWF/00Z UKMET/00Z Canadian Monday and Tuesday in a
pattern with above normal forecast uncertainty. For later next
week, more of the 06Z GEFS and 00Z ECMWF ensemble means were used.
The 06Z GFS appears much too fast with the frontal progression
across the Plains. The 06Z GEFS was slower than than its
deterministic solution, while the ECMWF was slower than its
ensemble mean and the GFS solutions.
Kong/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