Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
324 PM EDT Fri May 17 2019
Valid 12Z Mon May 20 2019 - 12Z Fri May 24 2019
...A Stormy and Wet Pattern for the Western and Central U.S next
week....
...Overall Weather Pattern...
It remains the case that a stormy and unsettled weather pattern is
expected across much of the central U.S. during the medium range
period with a large scale upper trough becoming established over
the Intermountain West and a building upper level ridge over the
southeastern states. Three well defined storm systems are expected
next week, with the first affecting the northeastern U.S. on
Monday. The second storm exits the snowy Rockies Monday to gather
strength across the Plains on Tuesday and tracks towards the Great
Lakes, and the third well organized system slams into the West
Coast Tuesday, develops over the Intermountain West midweek to
reach the Plains late next week.
...Guidance/Predictability Assessment...
The 06 UTC FV3 and 00 UTC ECMWF forecasts are well clustered with
GEFS/ECMWF ensemble solutions through this medium range period,
bolstering confidence. The WPC medium range product suite was
primarily derived from a seemeingly reasonable composite blend of
these guidance pieces. This also maintains good WPC continuity. In
contrast, the 00/06 UTC GFS runs offer more outlier solutions
that become much more progressive than the WPC composite from the
Gulf of Alaska to western Canada and the northwestern U.S.
mid-later next week. This does not seem as good a fit with the
overall amplifying pattern.
...Weather Highlights and Hazards...
Numerous showers and thunderstorms continue to be in the forecast
going into next week across the central/southern Plains and
extending to the Upper Midwest. Multiple rounds of MCS activity
are likely with both of the low pressure systems that are progged
to track across the Plains. This will have the potential to
produce very heavy rainfall capable of flash flooding, and severe
weather is also likely from northern Texas to the Midwest based on
recent SPC forecasts. The greatest chance of flooding would be
from the Texas Panhandle region to Iowa with the strong low
pressure system for the early to middle part of the week.
Additional heavy rain is also possible from the next storm system
tracking eastward from the Intermountain West later in the week,
although details on timing and placement are less certain.
There will also be a dichotomy of temperature anomalies given the
amplified flow pattern in place. Temperatures are expected to be
well above normal across much of the southeastern U.S. owing to
the strength of the upper ridge, and this will also serve to keep
rainfall chances minimal. The opposite will be the case across
much of the western U.S. and also the northern Plains that will be
under the influence of the upper level trough and to the north of
the low tracks. Heavier late season snows are also likely for the
Sierra Nevada to the northern Rockies.
D. Hamrick/Schichtel
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 rain across portions of the Plains and the Mississippi
Valley, Mon-Tue, May 20-May 21.
- Severe weather across portions of the Central and Southern
Plains, Mon, May 20.
- Severe weather across portions of the Central Plains and the
Middle Mississippi Valley, Tue, May 21.
- Flooding possible across portions of the Central and Southern
Plains and the Mississippi River Basin.
- Flooding occurring or imminent across portions of the Central
Plains, the Mississippi and Missouri River Basins, and the
Northern Rockies.
- Flooding likely across portions of the Northern Great Basin.
- Excessive heat across portions of the Southeast, Thu-Fri, May
23-May 24.
- High winds across portions of the Southern Rockies and the
Southern High Plains, Mon, May 20.
- Much below normal temperatures across portions of California,
the Central Great Basin, and the Southwest, Mon-Wed, May 20-May 22.
- Much below normal temperatures across portions of the Northern
and Central Plains, Mon-Tue, May 20-May 21.
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