Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
306 PM EDT Thu Jun 20 2019

Valid 12Z Sun Jun 23 2019 - 12Z Thu Jun 27 2019

...Weather Highlights/Threats...

The upper ridge redeveloping over the southeast CONUS for the rest
of the work week will prime the southern Plains and lower MS
Valley with heat and moisture ahead of a trough that swings across
the central CONUS Sunday through Tuesday. Forcing ahead of the
trough crossing the Rockies this weekend presents a threat of
strong to severe/MCS convection and locally heavy rains in areas
with pooling moisture/instability. The heavy rainfall focus Monday
and Tuesday is forecast to be from Oklahoma across the lower MS
Valley and south to east Texas. Widespread rain is also forecast
across the Midwest in this time. The rainfall focus shifts to New
England along a warm front lifting north ahead of the low crossing
the Great Lakes Tuesday night into Wednesday night.

Expect above normal temperatures (particularly for minimums)
across the southern Mississippi Valley and the Southeast/TN
Valley/OH Valley/Appalachians on Sunday,  continuing across the
Northeast through Tuesday. After initial cold in the high Plains
and Rockies, temperatures moderate early next week. Then another
area of warmer than normal temperatures develops as an upper ridge
builds across the northern Plains through the middle of next week,
with anomalies as much as ten degrees above normal by Thursday in
the Dakotas and MN. A low pushing south along the Pacific
Northwest coast leads to a cooling trend next week across much of
the west, with widespread temps several degrees below normal,
focused on across the West Coast on Wednesday, pushing inland to
the Great Basin and interior Pacific Northwest on Thursday. 


...Guidance/Predictability Assessment...

The WPC medium range product suite was derived from a blend of the
00 UTC deterministic ECMWF/UKMET and 00 UTC ECENS/06 UTC GEFS
ensemble mean guidance. The 06 UTC deterministic GFS remains in
its long term bias of moving the 500 mb wave out of the central US
faster than the ECMWF/UKMET (as well as the CMC) and the ECMWF and
GEFS Means starting on Sunday. There is some uncertainty with the
progression of this shortwave trough/low across the Great Lakes
Monday and Tuesday. The 00 UTC ECMWF is more amplified with the
500 mb trough and possible embedded closed low across the upper MS
Valley Mon and Great Lakes Tue that caused the ECMWF to be the
slowest of the guidance envelope. Most ECMWF and GEFS members
cluster in between the ECMWF and GFS, so the preferred solution
has increasing weights toward the means through time.

Next week, a closed low moves southeast from the Gulf of Alaska
into the Pacific Northwest, coming ashore by the middle of next
week. This persistent and slow moving circulation allows the deep
layer ridge to rebuild over TX and NM, and then extend north into
the northern Plains. There is less spread than normal for this
consensus, lending the situation to a consensus based approach.

Jackson


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 Central Plains, the Middle
Mississippi Valley, the Lower Mississippi Valley, the Southern
Plains, and the Tennessee Valley, Sun-Mon, Jun 23-Jun 24.
- Flooding possible across portions of the Central Plains, the
Middle Mississippi Valley, the Southern Plains, and the Ohio
Valley.
- Flooding occurring or imminent across portions of the Central
Plains, the Lower Mississippi Valley, the Tennessee Valley, the
Middle Mississippi Valley, the Southern Plains, and the Ohio
Valley.
- Flooding likely across portions of the Central Great Basin and
the Ohio Valley.
- Excessive heat across portions of the Southern Plains, Sun-Mon,
Jun 23-Jun 24.
- Excessive heat across portions of the Southeast and the
Mid-Atlantic, Sun-Tue, Jun 23-Jun 25.
- Much below normal temperatures across portions of the Southern
Rockies, the Central Rockies, the Central Great Basin, the Central
Plains, and the Southwest, Sun, Jun 23.

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