Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
255 AM EDT Tue Mar 31 2020
Valid 12Z Fri Apr 03 2020 - 12Z Tue Apr 07 2020
...Overview and Guidance/Predictability Assessment...
An immensely strong upper high over far northern Canada will
meander in place as an upper low over southwestern Canada rotates
impulses about its center of circulation. This will drive a lead
system out of the Plains Friday slowly to the East Coast by Sunday
with several Pacific systems coming into the West. The
models/ensembles continue to show better agreement on at least the
first few days of the forecast, and a blend of the deterministic
guidance sufficed (though the 18Z GFS was notably quicker into
NorCal 12Z Sat). Thereafter, large disagreement near Alaska enters
the area off WA/OR late Sat into Sun and perhaps into California
by Monday. Trended quickly toward much more ensemble weighting by
next Mon as the trough (or upper low) reaches the coast, then
fully to the 12Z ECMWF ensemble mean as spread continued to
increase beyond reasonable amounts to facilitate any deterministic
inclusion.
...Weather/Hazard Highlights...
Rainfall will focus along/ahead of a north-south orientated cold
front and east of the dryline on Texas, some of which could be
locally heavy across south Texas. Marginally cold air on the
northwest side of the main surface low supports a modest snow risk
from the end of the short range to the beginning of the medium
range across Minnesota. Precipitation will become lighter farther
east over the Great Lakes/Northeast with more appreciable rainfall
possible along the Gulf Coast.
Meanwhile, the Pac NW will see some general light rain/snow as a
couple lead systems move through with the potential for more
organized activity through CA (especially the Sierra). Depending
on the speed/depth of the trough through the West, precipitation
could focus southward to southern California into the Great Basin
by the end of the period.
Fracasso
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