Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1212 AM EDT Sat Mar 23 2019
Valid 12Z Tue Mar 26 2019 - 12Z Sat Mar 30 2019
...Guidance Assessment/Preferences...
Models and ensembles seem reasonably compatable into Days
3-4/Tue-Wed and a favored composite solution de-emphasizes the
less predictable smaller scale features. While guidance overall
continues to offers a fairly similar larger scale CONUS and
vicinity pattern evolution over for much of next week, run-run
variance with a multitude of mid-smaller scale embedded systems
and stream interactions do grow quickly with time. This is
especially evident with recent GFS and to a lesser extent FV3 runs
that do not cluster as well with latest GEFS/ECMWF ensembles as
the ECMWF. Variance seems to mainly stem from differences in the
handling of east-Pacific trough energies. Prefer to maintain WPC
and guidance continuity better with a 18 UTC GEFS mean and 12 UTC
ECMWF/ECMWF ensemble mean blended forecast approach day 5-7.
...Weather Highlights and Hazards...
A southern stream front with moisture and enhanced precipitation
focusing waves ejects across the Southeast into Tuesday. The
frontal low/coastal wave will cut underneath and interact with a
cooling northern stream frontal drape overtop whose deepened
post-frontal high pressure then settles down through the central
and eastern U.S. Meanwhile, a protracted series of Pacific systems
with associated height falls and enhanced precipitation swaths are
slated to track onshore and across much of the West through next
midweek ahead of an mean closed low/trough reinforced just off
West Coast. Heaviest precipitation/heavy mountain snows threaten
northern California/Oregon through the northern Rockies. It is
expected that the bulk of Pacific trough energy will eject through
the West Wed/Thu to emerge over the Plains into later next week to
induce cyclo/frontogenesis. This may occur just as a renewed
northern stream may force cool air down into the unsettled
n-central states. This airmass would prove to be in stark contrast
to a rapidly warming airmass spreading from the east-central U.S.
to eastern U.S. into next weekend. Deepening return flow from the
Gulf of Mexico would fuel an expanding risk of enhancing
rains/convection to channel between the approaching fronts and
slowly retreating eastern U.S. high pressure. 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 developent continues to grow.
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