Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
205 AM EDT Thu Jun 10 2021
Valid 12Z Sun Jun 13 2021 - 12Z Thu Jun 17 2021
...Record to dangerous heat this weekend into early next week
across much of the interior West/Northern Plains...
...Extreme heat possible for the Southwest next week...
...Overview...
Anomalously strong upper ridge building and amplifying through the
central U.S. into next week will continue the much above normal
temperatures across much of the West into the Northern Plains.
Record heat will be possible early next week from the Southwest to
Northern Plains where the repeated days of heat will become
excessive and dangerous. Troughing exiting New England will dig
back into the East next week supporting a couple cold frontal
passages and a chance of showers/storms. A Pacific front will push
into the Pacific Northwest early next week and head into Canada.
...Guidance/Predictability Evaluation...
The amplified flow pattern holding over the CONUS during the
medium range period (Sunday-Thursday) has above average model
predictability and forecast confidence. A 594+ dm upper high
expands over the Four Corners and central Rockies next week
contributing to a +3 sigma 500 mb height anomaly which is well
clustered with the available deterministic guidance. Shortwave
energy downstream will help carve out more troughing over the
Great Lakes to Northeast, especially by Tuesday onward. A
shortwave trough rounding the base of the western trough will
eject into the Northern Rockies days 6-7. Finally, over the Gulf,
a weakness between the Southwest and NW Caribbean ridges/highs
will take a feature southwestward into Mexico, perhaps enhancing
some rainfall over the open waters. With the above average model
agreement, the WPC blend this cycle utilized a mostly
deterministic blend compromised of the 18Z GFS and 12Z
ECMWF/CMC/UKMET with some inclusion of the ECENS/GEFS for day 7 to
account for some slightly higher model spread.
...Weather Highlights/Hazards...
The upper ridge over the central U.S. will keep temperatures much
above normal from portions of the Southwest to the Northern
Rockies/Plains late this weekend through much of next week.
Departures from normal of 15F to 25F will be common with daily
records likely to be set Monday-Wednesday. High temperatures well
into the 110s will be possible across the Southwest while upper
90s to low 100s will be possible from Utah into portions of the
Northern Plains and Northern Rockies. Little relief at night is
expected with nighttime lows 10F to as much as 20F above normal.
The repeating days of this type of heat, especially for areas in
the northern tier unaccustomed to prolonged heat waves, will
become dangerous for sensitive groups.
Elsewhere across the CONUS, temperatures are expected to be near
to slightly above normal, perhaps a bit below normal over the
Great Lakes into the Northeast next week behind a cold front. The
strong/dominant upper ridge over the central CONUS will keep much
of the area void of significant or heavy rainfall -- the
exceptions being over the Northwest as a front moves in this
weekend and possibly along the Gulf Coast to Southeast U.S. late
this weekend into early next week where a frontal boundary stalls
and lingers.
Taylor
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook 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