Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
450 PM EDT Mon Apr 08 2019
Valid 12Z Thu Apr 11 2019 - 12Z Mon Apr 15 2019
...Major winter storm tracking from the central Plains into Upper
Great Lakes Thu-Fri...
...Heavy rainfall threat from eastern Texas/Lower Mississippi
Valley northeastward during the weekend...
...Overview and Guidance Assessment/Preferences...
Guidance continues to show a moderately progressive pattern
consisting of embedded strong/impactful systems. The forecast
based on new 00Z-06Z guidance follows a similar approach to
continuity, maintaining greater weight toward ECMWF/ECMWF mean
solutions that show greater/slower digging of shortwave energy
over the West versus GFS runs late this week followed by somewhat
slower ejection into the central/eastern states. Confidence is
only moderate at best though. Some 00Z GEFS members were actually
quite slow for the system heading into the central/eastern states
by late period but the 06Z GEFS has trended faster toward (but not
quite to) the ECMWF mean. Also, there has been a notable trend in
most guidance toward faster arrival of upstream Pacific energy
into the Northwest by around day 6 Sun and the overall pattern
suggests the potential for faster progression over the East by
early next week. The trend for upstream flow is fairly recent so
would like to wait at least another cycle before making any
significant adjustments. There is reasonable agreement for the
strong storm tracking from the Plains through the Great Lakes late
this week. Based on forecast considerations the blend started
with an operational model consensus on day 3 Thu, then replaced
06Z GFS input with the 06Z GEFS mean completely by day 5 Sat,
followed by a focus primarily on the 00Z ECMWF-ECMWF mean/06Z GEFS
mean on days 6-7 Sun-Mon.
...Weather Highlights/Hazards...
Consensus still displays a high potential for significant snowfall
and strong winds--leading to a period of blowing snow and possible
blizzard conditions--from the north-central Plains into the Upper
Great Lakes during the latter half of the week. Some strong to
severe convection will be possible farther south/southeast in the
warm sector. The late week/early weekend system digging into the
West will spread rain and high elevation snow across the region.
The greatest uncertainty will be the extent and intensity of
precipitation over/near Arizona, due to sensitivity to exact
amplitude and timing of the upper trough. Ejection of this system
will lead to a heavy rainfall threat from eastern Texas and the
Lower Mississippi Valley region into parts of the Mid-Atlantic and
southern New England, and possibly including the Ohio Valley. The
southwestern part of this broad area has the higher confidence due
to a period of moist low level Gulf inflow intersecting a front
stalled over the Gulf Coast (originally trailing from the late
week Plains storm). The Pacific Northwest may see additional
precipitation after the late week system in association with
frontal systems pushed along by progressive flow aloft.
The most extreme temperature anomalies will be of the cold variety
over the Rockies/Plains Thu-Sat, behind the initial Plains-Great
Lakes storm and then in easterly upslope flow ahead of the next
system ejecting out of the West. Some highs may be 20-30F below
normal for one or more days. Also during Thu-Sat expect above
normal temperatures over the East, especially for morning lows
which may be 10-20F above normal at some locations. Expect
readings to moderate over much of the Lower 48 by next Mon.
Rausch
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
Hazards:
- Heavy precipitation across portions of the Pacific Northwest,
Thu, Apr 11.
- Heavy precipitation across portions of the Pacific Northwest and
the Northern Great Basin, Sat-Mon, Apr 13-Apr 15.
- Heavy precipitation across portions of the Central Rockies and
the Central Great Basin, Fri-Sat, Apr 12-Apr 13.
- Heavy precipitation across portions of the Central Plains, the
Middle Mississippi Valley, the Great Lakes, the Upper Mississippi
Valley, and the Northern Plains, Thu-Fri, Apr 11-Apr 12.
- Heavy rain across portions of the Mid-Atlantic, the Lower
Mississippi Valley, the Central Appalachians, the Tennessee
Valley, the Great Lakes, the Middle Mississippi Valley, the
Northeast, the Southern Appalachians, the Southeast, the Southern
Plains, and the Ohio Valley, Sat-Sun, Apr 13-Apr 14.
- Heavy rain across portions of the Great Lakes and the Ohio
Valley, Fri, Apr 12.
- Heavy snow across portions of the Northern Rockies, Sun-Mon, Apr
14-Apr 15.
- Heavy snow across portions of the Central Plains, the Great
Lakes, the Upper Mississippi Valley, and the Northern Plains,
Thu-Fri, Apr 11-Apr 12.
- Severe weather across portions of the Middle Mississippi Valley,
the Lower Mississippi Valley, the Great Lakes, the Ohio Valley,
and the Tennessee Valley, Thu, Apr 11.
- Flooding possible across portions of the Lower Mississippi
Valley, the Great Lakes, the Upper Mississippi Valley, and the
Northern Plains.
- Flooding occurring or imminent across portions of the Lower
Mississippi Valley, the Northern Plains, the Tennessee Valley, the
Northern Rockies, the Middle Mississippi Valley, the Northern
Great Basin, the Upper Mississippi Valley, the Pacific Northwest,
and the Ohio Valley.
- Flooding likely across portions of the Northern Plains, the
Tennessee Valley, the Pacific Northwest, the Northern Great Basin,
the Upper Mississippi Valley, and the Southern Plains.
- High winds across portions of the Central Plains, the Central
Rockies, the Lower Mississippi Valley, the Northern Plains, the
Southern Rockies, the Middle Mississippi Valley, the Upper
Mississippi Valley, the Southern Plains, and the Southwest, Thu,
Apr 11.
- Much below normal temperatures across portions of the Central
Plains, the Central Rockies, the Northern Plains, the Southern
Rockies, the Upper Mississippi Valley, and the Southern Plains,
Thu-Sat, Apr 11-Apr 13.
- Enhanced wildfire risk across portions of the the Southern
Plains and the Southwest, Thu, Apr 11.
- Heavy precipitation across portions of mainland Alaska and the
Aleutians, Thu, Apr 11.
- High winds across portions of mainland Alaska and the Aleutians,
Thu, Apr 11.
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