Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Fri Aug 23 2019
Valid 12Z Mon Aug 26 2019 - 12Z Fri Aug 30 2019
...Weather Pattern Overview...
Broad cyclonic flow aloft is expected across the northern tier of
the nation for much of the upcoming week as an upper level low
develops over southern Canada and then Hudson Bay. This is
expected to result in a broad upper level trough over the northern
Plains and extending to the Great Lakes with a Canadian surface
high in place. Upper level ridging extending from Texas to
California is expected to continue through midweek, and also
across the western Atlantic Ocean.
...Model Guidance Evaluation...
Models and ensemble means are in relatively good agreement at the
beginning of the forecast period, with the GFS a little more
amplified with the trough axis over the northern Plains. The 00Z
ECMWF has trended more in line with the model consensus regarding
the evolution of the upper low over Manitoba by Tuesday compared
to its 12Z run, which was a bit farther south. Noteworthy model
differences become apparent across British Columbia by Tuesday
regarding timing and amplitude of shortwave energy in northwest
flow, with the ECMWF supporting more of a ridge axis and the CMC
and GFS indicating a shortwave trough. This leads to
uncertainties in timing of cold front passage across the Plains
and then the Ohio Valley. There is also a growing model signal
for a potential tropical disturbance to pass between the East
Coast and Bermuda on Tuesday, and the National Hurricane Center
will have additional information on that.
...Sensible Weather...
A hint of fall is expected across the north-central U.S. next week
with high temperatures generally 5 to 15 degrees below normal,
which equates to readings topping out in the middle 60s to middle
70s for much of this region. It should continue feeling like the
middle of summer from Texas to the Great Basin and the Desert
Southwest with temperatures 5 to 15 degrees above normal, with the
greatest anomalies expected early next week across western Texas
and New Mexico. High temperatures could exceed 110 degrees across
the lower elevations of southern Arizona and southeast California
on Monday and Tuesday.
Areas of moderate to locally heavy rainfall will be possible ahead
of the cold front crossing the Upper Midwest and Great Lakes
region early in the week, with possible convective complexes that
may produce 2 inches of rainfall through early Tuesday. For
midweek and beyond, model uncertainty reduces confidence in
placement of heaviest rainfall areas. However, there is a good
chance of a corridor of enhanced rainfall across the central
Plains later in the week near the trailing end of the front.
Hamrick
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