Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
237 AM EDT Wed May 01 2019
Valid 12Z Sat May 04 2019 - 12Z Wed May 08 2019
...Guidance/Predictability Assessment ...
WPC medium range surface/fronts and 500 mb progs were mainly
composed from a composite of compatable GFS/ECMWF/UKMET/Canadian
mid-larger scale mass field guidance this weekend. Transitioned to
an ensemble mean based forecast early-mid next week amid growing
forecast spread and uncertainty. This blended solution acts to
mitigate embedded smaller scale impulse timing and convection
genesis uncertainties and maintains good overall WPC continuity.
The WPC forecast did favor ECMWF/ECMWF ensembles precipitation
that better fit the flow in showing more southward convective
tendancies into deepening moisture.
...Weather Highlights/Threats...
A slow moving and wavy trailing front will pool moisture to fuel a
risk of locally heavy rains/thunderstorms with cell training and a
local runoff issue focus from the Lower Mississippi Valley to the
Mid-Atlantic this weekend.
Upstream, closed low/trough energy and height falls are expected
to move inland into CA/Southwest early next week in the split
southern stream. This may support scattered CA to Great
Basin/Rockies convection. Flow progression may then renew lead
convective focus downstream over the south-central U.S.
Meanwhile, northern stream systems will meanwhile progress over
southern Canada and effect the U.S. northern tier. These would
support precipitation/convection ahead of a cooling/unsettling
main closed low/trough and lead weather focusing surface frontal
systems. This amplified main system will track from s-central
Canada this weekend to eastern Canada early next week. A stalling
trailing front underneath into will periodically focus impulse
driven convection over the northern Rockies, central Plains, and
from the Midwest to the Northeast.
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