Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
141 AM EST Sat Mar 09 2019
Valid 12Z Tue Mar 12 2019 - 12Z Sat Mar 16 2019
...North-Central U.S. Heavy Snow Threat Wed-Thu...
...South-Central to Mid-South/Southeast U.S. Heavy Rain Threat
Tue-Fri...
...Overview...
Another potent storm system will trek out of the Southwest/Four
Corners region Tuesday and lift northeastward toward the Great
Lakes by Thursday. This will spread a large area of potentially
heavy rain from the southern Plains eastward into the Southeast
while marginally cold air to the north will support a heavy
snowfall threat over the High Plains and Upper Midwest. By the
start of next weekend, the pattern appears to be much quieter with
high pressure forecast to dominate the western/central parts of
the lower 48.
...Guidance and Uncertainty Assessment...
The ECMWF has led the way with the timing of the system out of the
Southwest, but the GFS (especially the 18Z FV3-GFS) clustered well
with the 18Z GEFS mean and the 12Z ECMWF/ECMWF ensemble mean so
that a blend/consensus position offered a reasonable starting
point. By next Fri/Sat, the upstream Pacific will become more
uncertain as the shape of the upper ridge into British Columbia
will dictate the amount/strength/orientation of troughing in the
west/Rockies.
...Weather Highlights and Hazards...
Main system of interest in the medium range will lift out of the
Southwest and deepen quite smartly into southeastern Colorado by
Wednesday morning. Precipitation will expand in coverage out of
Arizona and New Mexico eastward, focused on the central/southern
Plains (northern Texas northward) Tue/Wed. To the east, a front
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. The potential for
several inches of rain exists over a large area that will be
further refined over the next several days, but atmospheric and
ensemble signals continue to be strong. 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 will receive significant snow in the short term (e.g.,
southern Minnesota). 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 perhaps
moderate just a bit by next weekend. In the east, post-front
airmass Tuesday will be chilly (below average by a few degrees)
but then warm up ahead of the central states' system by Thursday
into Friday.
Fracasso
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