Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
918 AM EDT 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...
An amplified flow pattern will remain quite active Wed/Thu as
another central U.S. system heads toward the Great Lakes with a
potpourri of weather threats typical of a robust late winter/early
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 with most unsettled flow over a cooled Northeast and
wet Florida near a stalled trailing front.
...Guidance and Uncertainty Assessment...
Deterministic and ensemble guidance remain unusually well
clustered into next weekend and a composite blend seems to offer a
very reasonable forecast that maintains excellent WPC continuity.
Predictability in this pattern is quite high.
...Weather Highlights and Hazards...
The main system of interest in the medium range will lift out of
southeastern CO Wed morning as precipitation expands in coverage
eastward, focused from eastern portions of the southern/central
Plains and mid-lower MS Valley to the TN Valley Wed. This will
include a risk of severe weather given height falls/jet
dynamics/diffluence aloft and lower atmospheric
inflow/convergence. To the east, a lead frontal boundary will lift
northward as a warm front and bring widespread rains and embedded
convection to AL/GA/TN/KY then south-central Appalachians Thu/Fri.
To the north, enough cold air will support heavy snow on the
northwest/north side of the surface low that will occur with
strong winds (possible blizzard conditions). Heavy cold rains will
fall to the southeast of the surface low over some areas that will
have received significant snow in the short term (i.e. 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. This activity may be
reinforced with weekend approach of shortwave energy digging well
to the lee of an amplifying western Canadian upper ridge.
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