Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
155 AM EST Sun Mar 10 2019
Valid 12Z Wed Mar 13 2019 - 12Z Sun Mar 17 2019
...Heavy Snow/Wind Threat for the North-Central U.S. Wednesday and
Thursday...
...Heavy Rain/Strong Thunderstorm Threat from the South-Central
Plains/MS Valley to the Mid-South/Southeast Wednesday to Friday...
...Overview...
Pattern will start quite active in the medium range Wed/Thu as
another central CONUS system heads toward the Great Lakes with a
potpourri of weather threats typical of a robust spring storm.
This will spread a large area of potentially heavy rain/severe
convection and runoff threat from the central/southern Plains
through the Mid-South/Southeast as marginally cold air to the
north supports a heavy snow/wind threat for the north-central
Rockies/Plains and Upper Midwest. By next weekend, the pattern
appears much quieter with high pressure forecast to dominate the
western/central parts of the lower 48 as broad troughing lingers
in the east.
...Guidance and Uncertainty Assessment...
Most of the GFS/ECMWF deterministic/ensemble guidance clustered
well through the period so that a blend could be utilized through
about Friday. For next weekend, preferred a mostly ensemble-based
solution given disagreement on the shape/details of the upper
trough in the east as well as back over the Southwest.
...Weather Highlights and Hazards...
Main system of interest in the medium range will lift out
southeastern Colorado Wednesday morning as precipitation expands
in coverage eastward, focused on the central/southern Plains
(northern Texas northward) Tue/Wed. To the east, boundary across
the Gulf will lift northward as a warm front and bring widespread
rainfall and embedded convection into the Mississippi/Tennessee
Valley Wednesday then into Alabama/Georgia/southern Appalachians
Thursday into early Friday. The potential for several inches of
rain exists over a large area that will be further refined over
the next few days. To the north, cold enough air will support snow
on the northwest/north side of the surface low that will occur
with strong winds (i.e., possible blizzard conditions). A cold
rain (perhaps over an inch to an inch and a half) will fall to the
southeast of the surface low over some areas that have received
significant snow in the short term (e.g., ND/SD/MN intersection).
The surface low will depart through southern Canada Friday as
colder air is dragged in behind it across the Great Lakes,
enhancing lake-effect snows.
Temperatures will remain below average in the west but moderate by
next weekend as upper ridging slowly noses into the area. In the
east, seasonable temperatures Wednesday will warm up ahead of the
central states' system by Thursday into Friday, only to retreat
back to near or just below climo values by next weekend.
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