Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1152 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
Friday...
...Heavy rainfall threat from eastern Texas/Lower Mississippi
Valley northeastward during the weekend to Monday...
...Overview and Guidance Assessment/Preferences...
The robust storm system over the Great Lakes region will continue
to lift north and east into Canada spreading wintry precipitation
along with it. As the central low pressure exits/weakens the wind
speeds will begin to relax over the northern U.S. Meanwhile, a
system will exit the Southwest/Southern Rockies this weekend
bringing widespread rain to much of eastern Texas, Lower
Mississippi and western Tennessee Valley with the potential for
excessive rainfall and flash flooding. A surface low is expected
to form along the boundary and aid in the progressive track toward
the Ohio Valley. Model guidance suggest that this system will
occlude, with a new low forming near the mid Atlantic coast and
proceeding northeast near or off the New England coast early next
week.
Multiple shortwaves moving onshore the Pacific Northwest over the
course of the coming week will bring precipitation to the coasts
of Washington and Oregon and elevated snow to the Cascades. This
energy will translate over into the Northern High Plains.
The latest runs of the GFS have been faster/east than the rest of
the operational solutions. Although the trend over the last few
cycles have favored a more progressive track as it reaches the
eastern U.S., the GFS has been too quick. As such the use and
weighting of it was relatively light early on and negligible after
Sunday. The CMC, UKMET and the ECWMF were much better clustered
over most of the CONUS and picked up more details of the system
leaving the Great Basin and entering the Southern/Central Plains.
...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 Friday. Some
strong to severe convection will be possible farther
south/southeast in the warm sector in the Ohio Valley Thursday.
The 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
Friday-Saturday, behind the initial Great Lakes storm (peaking
20-25 degrees below normal in the central to northern Central
Plains. Also during Friday-Saturday 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 Saturday. 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.
Campbell
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