Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
323 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...
Although the majority of the heavy rain and snow will have likely
abated some by the beginning of the forecast period on Sunday,
areas of rain and thunderstorm activity will continue across much
of the Gulf Coast region and along the immediate East Coast.
Heavy snow is still expected across interior portions of New
England as the surface low lifts northeastward across eastern
Canada, and some lake enhanced snow will be possible. Some severe
thunderstorms will also be possible across parts of the Southeast
on Sunday ahead of the cold front, and this is something that the
Storm Prediction Center is continuing to monitor.
Looking ahead for early-mid week, 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 is expected to develop across the
central and southern Plains to the Mississippi Valley/Midwest
during the Tuesday and Wednesday time period as the trough induces
another deepening 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.
Another round of heavy snow and potential blizzard conditions is
becoming more probable across parts of the central plains and the
Upper Midwest as the surface low intensifies and colder air in
drawn in behind the low.
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