Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Sun Mar 24 2019
Valid 12Z Wed Mar 27 2019 - 12Z Sun Mar 31 2019
...Overview...
A closed eastern Pacific upper trough will reach the West midweek,
with height falls working eastward over the nation Thu-next Sun.
Surface fronts in the West will support some heavy precipitation
including heavy elevation snows, and low developments in the
Plains and subsequent movement through the MS Valley/Midwest may
combine with a surge of deepening moisture/warmth from the Gulf of
Mexico to fuel some enhanced rain/thunderstorms in those areas
later week. The pattern also includes a risk of wrap-around
post-frontal snows on the cooled northwest periphery of the main
precipitation shield.
...Guidance Assessment/Preferences...
A multi-model blend has been working well into day 3/4 for the
large-scale features while de-emphasizing the small-scale
differences in the forecast models were in general agreement for
the upper low in the eastern Pacific moving eastward into the
CONUS. Prefer an ensemble mean forecast approach days 5-7 in a
period of growing forecast spread, leaning more on ECMWF ensemble
mean to maintain max WPC continuity.
...Weather Highlights and Hazards...
With the upper trough/low approaching the West, a couple of fronts
will make their way through the West and some heavy precipitation
is expected Wed/Thu. Heavy valley rain/mountain snows will
threaten northern California/Oregon through the northern Rockies,
with heavy snow forecast for the Central Rockies into later week.
As the trough energy ejects out through the West, it is expected
to induce cyclo/frontogenesis in the Plains. This plus another
cold front dropping southward out of Canada in tandom with
deepening lead return flow from the Gulf of Mexico would fuel an
expanding risk of enhancing rains/convection. The emerging heavy
rain area threatens areas of the Mississippi Valley/Midwest (where
flooding is ongoing) heading into next weekend. Uncertainty
remains regarding heaviest rainfall amounts/placement, but the
guidance signal for development continues to grow. In the cold air
behind the aforementioned cold front coming from Canada,
late-season snow is possible in the Northern/Central Plains to
Midwest.
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