Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
151 AM EDT Tue Apr 30 2019
Valid 12Z Fri May 03 2019 - 12Z Tue May 07 2019
...Flooding/Flash Flooding Threat Lingers for the Southern
Plains/Lower Mississippi Valley...
...Guidance/Predictability Assessment and Weather
Highlights/Threats...
The WPC medium range product suite was mainly derived from a
composite of reasonably well clustered GFS/ECMWF/UKMET/Canadian
and ensemble mean mid-larger scale guidance. This blended solution
acts to mitigate embedded smaller scale impulse timing and
convection genesis uncertainties and maintains good overall WPC
continuity with respect to potential weather related hazards.
A lead and wavy frontal system with moderate precipitation will
progress Fri/Sat across the East as powered by an ejecting
shortwave trough aloft. A wavy trailing front will stall across
the U.S. southern tier and pooled moisture and convection offers a
daily threat of heavy rains/thunderstorms and cell
training/locally enhanced runoff issues with hard to time southern
stream impulse passages. Pacific closed low/trough energy and
height falls are also expected to work inland into CA by early
next week in this split southern stream. This may support
scattered Southwest to Rockies convection and then renew lead
convective focus downstream over the south-central U.S. Strong to
severe thunderstorms with some heavy rain and flash
flooding/flooding potential will periodically threaten the
Southern Plains and Lower Mississippi Valley in this lingering
pattern. Flooding remains possible as particularly the Mississippi
Valley and vicinity has had flooding concerns for weeks, and with
the convective nature of the precipitation flash flooding is
possible as well.
Meanwhile, leading northern stream shortwaves overtop are expected
to progress from the Northwest eastward across the U.S. northern
tier. This will support modest system/precipitation development in
advance of a cooling/unsettling main closed low/trough and lead
weather focusing surface frontal system. This amplified system may
track from western Canada Fri to s-central Canada/Upper Midwest
Sun to eastern Canada and the Northeast in about a week. The
baroclinic zone with the stalling trailing front may periodically
focus impulse driven convection mainly over the northern Rockies,
central Plains, and Ohio Valley.
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