Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1151 AM EDT Sun Apr 14 2019
Valid 12Z Wed Apr 17 2019 - 12Z Sun Apr 21 2019
...Yet another major spring storm mid-late week will pack a heavy
rainfall and severe weather threat for the central to eastern
U.S...
...Overview...
Potent upper level low will exit the Four Corners region Wednesday
and work its way eastward/northeastward as ridging builds in the
western Atlantic. This will lead to a dynamic spring storm again
for the central states with rain, severe weather, and some
northern fringe snow. Ridging will also push into the West
Coast,to be partially replaced by an upper low tracking into
Southern CA into Saturday and shearing over the Southwest to the
southern Plains next Sunday with little fanfare. The system is
kicked out as more unsettling/wetter Pacific trough energies and
height falls dig back upstream and inland across the West Coast.
...Guidance Preferences...
06 UTC GFS/GEFS and 00 UTC ECMWF/ECMWF ensemble forecasts now
cluster extremely well and maintain good continuity days 3-7. WPC
progs were mainly derived from a composite blend of these guidance
pieces. Greater weighting was applied to the deterministic models
for extra detail consistent with a pattern with seemingly above
normal predictability. However, it remains a bit less certain the
extent the southern portion of the upper trough remains separated
from the flow to the north. The 00 UTC UKMET and especially the 00
UTC Canadian delay stream phasing compared to the GFS/ECMWF,
perhaps slowing the system down more by the weekend.
...Weather Highlights/Threats...
Significant precipitation will again increase into Wednesday and
spread from the Mississippi/Missouri Valleys through the East as
low pressure strengthens over the Plains and Corn Belt. Multi-inch
rainfall totals with local flooding are probable (enhanced in
embedded convection) both along/ahead of the front and to the
north/northeast of the surface low. Consult SPC for the latest on
the severe weather risk. Mild temperatures will precede the front
(10-15F above average) to be replaced by cooler than average
temperatures after its passage. Upstream, the Northwest will see a
front with modest precipitation push through the region Friday and
the weekend, reaching the Upper Midwest and stretched back to CA.
Fracasso/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