Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
114 AM EDT Tue Apr 09 2019
Valid 12Z Fri Apr 12 2019 - 12Z Tue Apr 16 2019
...Major winter storm tracking across the Upper Great Lakes Fri...
...Heavy rainfall threat from eastern Texas/Lower Mississippi
Valley northeastward during the weekend to Monday...
...Overview and Guidance Assessment/Preferences...
The medium range period starts with the tail end of the central US
major cyclone moving through the upper Great Lakes Fri and then
across the border into Canada Fri night, when the event winds down
over the US. The models and ensembles remain clustered so a
consensus based approach continues to be preferred.
Also on Fri, the system that will become a producer of widespread
precipitation in the lower MS Valley with flooding potential digs
south across the Great Basin towards the southwest, with a closed
500 mb low possibly near the NM/AZ border at 12z Sat.
The system moves east afterward on to the southern Plains and
lower MS Valley by Sun morning, a bit faster than the prior
cycle's dominant cluster of solutions.
Low pressure forms at the surface and moves steadily northeast
towards the Ohio Valley, with the system occluding and a new low
forming near the mid Atlantic coast and proceeding northeast near
or off the New England coast early next week.
The 12z ECMWF/12z ECMWF mean solutions show a slower progression
of the upper trough than the GFS runs this weekend into early next
week and remain preferred.
The 18z GEFS mean was an intermediate solution and given a
minority weighting to hedge the timing.
The guidance shows the arrival of upstream Pacific energy into the
Northwest by around day 5 Sun and into the northern Rockies on day
6 Mon, possibly reaching the high plains day 7 Tue 16 Apr. The
12z ECMWF/12z Canadian/18z GFS models all show differing timing
and phasing of the upper trough, so much greater weighting was
given to the respective ensemble means, although greater weighting
was given to the ECMWF Ensemble Mean for this forecast cycle.
...Weather Highlights/Hazards...
Consensus still displays a high potential for heavy snowfall and
strong winds--leading to a period of blowing snow and possible
blizzard conditions into the Upper Great Lakes Fri. Some strong
to severe convection will be possible farther south/southeast in
the warm sector in the Ohio Valley Thu. The late week/early
weekend system digging into the West will spread light valley rain
and high elevation snow across the region.
This system will lead to a heavy rainfall threat from eastern
Texas and the Lower Mississippi Valley region into the
Appalachians, Mid-Atlantic and southern New England, and possibly
including the Ohio Valley. The highest forecast rainfall amounts
are centered over the lower MS Valley.
The Pacific Northwest and northern Rockies should see additional
precipitation after the late week system in association with
frontal systems moving onshore and inland.
The cold temperature anomalies will be over the Rockies/Plains
Fri-Sat, behind the initial Great Lakes storm (peaking 20-25
degrees below normal in the central to northern central Plains.
Also during Fri-Sat expect above normal temperatures over the
East, especially for morning lows which may be 10-20F above normal
in the upper Ohio valley/Appalachians Fri and coastal mid Atlantic
to southern New England Sat. Expect readings to moderate over
much of the Lower 48 early next week, with slightly below normal
temps under the Rockies upper trough and above normal in return
flow in the southern to central Plains.
Petersen
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