Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
305 AM EDT Sun Oct 20 2019
Valid 12Z Wed Oct 23 2019 - 12Z Sun Oct 27 2019
...Guidance/Uncertainty Assessment and Weather
Highlights/Threats...
An energetic pattern supports several significant lower 48 weather
systems this week.
A lead upper trough will lift through the Northeast midweek as a
main deepened surface low works into Canada. Lingering
rains/runoff issues over the Northeast may be enhanced by
interaction and merging of a developing frontal wave from the
Mid-Atlantic with the extratropical remnants of Tropical Storm
Nestor. This scenario has high predictability.
Guidance also agrees that the flow pattern will meanwhile
reamplify well upstream as upper impulses/jet energies dig
progressively inland over the rapidly cooling West to support some
heavier snows into the n-central Rockies Wed/Thu.
Height falls should then act to carve out an amplified central
U.S. upper trough later week. Pattern evolution uncertainty grows
quickly however, lower forecast confidence. Latest guidance trends
are mixed, but there is an overall signal showing southern stream
separation to some degree later week into next weekend as the main
trough shifts over the central states with a possibility of closed
low formation that would drastically up the ante with respect to
subsequent rainfall potential and runoff threat from the South
northeastward into the Eastern Seaboard with deep return of Gulf
of Mexico and Atlantic mositure. WPC progs have trended to show
such potential. This is with consideration of the amplitude of
upstream upper ridging and as the next main kicker upper trough
does not bring unsettled weather/locally enhanced precipitation
through the Northwest until next weekend, so wavelength spacing
with the downstream system seems sufficient to allow for at least
some southern stream separation.
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