Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
159 AM EST Thu Mar 7 2019
Valid 12Z Sun Mar 10 2019 - 12Z Thu Mar 14 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 over the Great Lakes
region at the beginning of the forecast period Sunday will bring
widespread rain and thunderstorms to the eastern U.S. and snow for
the Upper Midwest and Great Lakes. The second Pacific disturbance
crosses the Desert Southwest on Monday and then undergoes
secondary cyclogenesis over the western High Plains by the middle
of next week with an evolution that is similar to the first storm
system.
...Guidance and Uncertainty Assessment...
The deterministic models are in good overall agreement regarding
the placement and overall strength of the surface low crossing the
Great Lakes region on Sunday, with the GFS slightly faster than
the model consensus, and quicker with cold front passage for the
East Coast. The speed differences are more apparent with the GFS
and also the GEFS mean with the mid week storm system across the
Plains. There is good model clustering among the CMC/ECMWF/FV3
solutions, and given that these are closer to WPC continuity
compared to the faster GFS/GEFS mean, the forecast was more in
line with the CMC/ECMWF/FV3.
Taking all of these factors into account, the forecast was
primarily derived from the 12Z ECMWF/18Z FV3/12Z UKMET for the
first three days, and then a slightly higher percentage of the EC
mean while still keeping a significant percentage of the
deterministic FV3, ECMWF, and some of the CMC as it relates to the
second low pressure system. The FV3 was substituted for the
operational GFS for this forecast period given the timing
differences noted. The WPC forecast is very similar to the
previous forecast in terms of track and expected low evolution.
...Weather Highlights and Hazards...
Widespread rain and thunderstorms are expected to develop from the
Gulf Coast to the Southeast U.S. on Sunday as a rich supply of
Gulf moisture surges northward ahead of a strong cold front from
the Midwest surface low.
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 through
the Mississippi Valley/Midwest in about a week as the trough
induces another deepening surface low/storm 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