Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
158 AM EST Wed Mar 6 2019
Valid 12Z Sat Mar 9 2019 - 12Z Wed Mar 13 2019
...Weather Pattern Overview...
An active weather pattern is expected during much of the medium
range period as two large scale troughs originating from the
Pacific lead to surface low development across the central U.S.
and Midwest states. The first storm system develops and
intensifies across the central plains and Upper Midwest this
weekend with surface high pressure exiting the East Coast region.
The second Pacific disturbance crosses the Desert Southwest on
Monday and then undergoes secondary cyclogenesis over the western
High Plains by the end of the forecast period next Wednesday.
...Model Guidance Evaluation and Preferences...
The agreement among the models and ensembles has continued to
improve on the synoptic scale for the entire forecast period with
the more amplified pattern that will be in place, and forecast
confidence is above average for this time period. The ECMWF, GFS,
FV3, and the EC and GEFS mean indicate rather impressive consensus
for a day 7 forecast regarding the second low to affect the
central part of the nation, with the CMC being the exception to
this by having the low well to the south across Texas. The CMC is
also to the west of the model consensus with the weekend storm
across the Upper Midwest. There has been a slightly faster trend
in the ensemble means for the weekend storm and slightly more
amplified with the storm system early-mid next week.
Taking all of these factors into account, the forecast was
primarily derived from the 12Z ECMWF/18Z FV3 and GFS/12Z UKMET for
the first three days, and then slightly higher percentages of the
EC and GEFS means while still keeping a significant percentage of
the deterministic GFS and ECMWF for the second half of the
forecast period. The WPC forecast is very similar to the previous
forecast.
...Weather Highlights and Hazards...
Widespread rain and thunderstorms are expected to develop from the
Gulf Coast to the Ohio Valley and southern Appalachians on
Saturday and into early Sunday as a rich supply of Gulf moisture
surges northward ahead of a strong cold front from the Midwest
surface low. The heaviest rainfall is likely from eastern Texas
to the southern Appalachians, where a general 1 to 2 inches of
rain is likely that may lead to some local flooding issues based
on the current forecast. However, the progressive nature of the
event should limit the duration of the heaviest rain. Depending
on where the surface low tracks, a corridor of blizzard conditions
is becoming increasingly likely across parts of the Upper Midwest,
including parts of the Dakotas. Another facet to this low
pressure system will be the potential for severe thunderstorms to
develop in the warm sector, and this is something that the Storm
Prediction Center is currently monitoring.
Upstream, the pattern again favors an amplified mid-upper level
trough developing off the West Coast this weekend. This will
support another round of precipitation over the southwestern U.S.
as the trough moves inland on Monday. Additional widespread rain
may then develop across the central and southern plains by the end
of the forecast period as the trough induces another surface low
east of the Rockies. There is also the potential for severe
weather with this storm system, and details on this will become
more evident in the upcoming days.
D. Hamrick
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