Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Tue Mar 26 2019
Valid 12Z Fri Mar 29 2019 - 12Z Tue Apr 02 2019
...Overview and Weather Highlights and Hazards...
Dynamic upper trough energy is slated to punch inland over the
West to the s-central Great Basin and Rockies by Friday. These
southern stream height falls will then work eastward over the
central and eastern states over the weekend, interacting with
amplifying northern stream trough energies digging down from
Canada. Plains cyclogenesis and subsequent movement through the MS
Valley/Midwest may combine with a lead surge of deepening
moisture/warmth from the Gulf of Mexico to fuel a period of
enhanced rain/thunderstorms in those areas with ongoing flooding
Friday into Saturday. There is also some risk of heavy snow
Fri-Sun on the cooled northwest to northern periphery of the
precipitation shield from the Northern/Central Rockies/Plains to
the Midwest/Great Lakes then northern New England.
...Guidance Assessment/Preferences...
Model and ensemble solutions seem reasonably well clustered Fri
into Sat for mid-larger-scale features and a composite blend
focuses less emphasis on the less predictable smaller scale
features. This blend includes the latest GFS, ECMWF, UKMET, and
Canadian that cluster well with the latest GEFS/ECMWF ensemble
means during this time period. Forecast spread and run-run
continuity issues become more problematic this weekend into early
next week. This begins with questions about the degree of
separation in the northern and southern streams, namely the manner
in which a deep upper trough in east-central Canada phases with
southern stream troughing traversing over the central CONUS.
Recent ECMWF runs/ECMWF ensemble means show more stream phasing
than recent GFS and to a lesser extent the FV3 and GEFS means.
Preferred a blend of the GEFS/ECMWF ensemble means given
uncertainty, but applied more weight to ECMWF ensembles for better
continuity into Day 7.
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