Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Thu Mar 31 2022
Valid 12Z Sun Apr 03 2022 - 12Z Thu Apr 07 2022
...Heavy rainfall/convection and runoff threat to focus across the
South next week...
...Pacific Northwest heavy rains and terrain/mountain heavy snow
threat inland to the northern Rockies...
...Guidance Evaluation/Predictability Assessment...
The WPC medium range product suite was mainly derived from a blend
of well clustered guidance from the 18 UTC GFS/GEFS mean, the 12
UTC ECMWF/UKMET/Canadian/ECMWF ensemble mean and the 01 UTC
National Blend of Models along with WPC continuity days 3-7
(Sun-next Thu). Embedded smaller scale system differences and run
to run continuity variances have become less problematic with the
18 UTC GFS/GEFS trending more in line than earlier runs,
especially into later period over the Pacific/Northwest. Newer 00
UTC guidance remains in close alignment. Overall, this seems to
bolster medium range forecast confidence to above normal levels,
albeit with the caveat that the energetic multi-system pattern is
also transitioning to higher amplitude/convective potential over
time that will likely vary the local threat focus.
...Overview and Weather Highlights/Threats...
Highly energetic Pacific flow will work increasingly inland from
the Northwest to the Rockies into early next week. This will act
to transport some deeper moisture in support of an emerging heavy
precipitation focus with rainfall over coastal and favrored
terrain of the Pacific Northwest. The pattern also favors periods
with terrain/mountain heavy snows from the Northwest to the
northern Intermountain West/Rockies prior to amplified upper ridge
building slated to build eastward over the West starting midweek.
Downstream progression and systems out from the West and
increasing northern stream phasing potential over time will
combine to support cyclogenesis/frontogenesis over the central and
eastern states next week. There is a growing guidance signal for
development of a building area of enhanced rainfall and some
threat to monitor for some severe convection across the
east-central U.S. (both especially across a more
unstable/convective South) early-mid next week as deeper Gulf
moisture returns and interacts with the complex series of wavy
fronts and a stalled lead front. Accordingly and considering
antecedent rainfall, WPC shows a "slight" risk on the newly
experimental medium range excessive rainfall outlook into Day 5
(ERO linked below). Guidance consensus has improved at longer time
frames with a well developed closed upper low forming over the
north-central U.S. by midweek as the pattern becomes amplified
downstream of the aforementioned building upper ridge over the
West. There is some potential then for some wrapping/overrunning
April snows from the Upper Great Lakes to the northern tier of the
Northeast.
Schichtel
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, experimental excessive rainfall
outlook, 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/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml