Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1136 AM EDT Tue May 28 2019
Valid 12Z Fri May 31 2019 - 12Z Tue Jun 04 2019
...Overview and Guidance Evaluation/Preferences...
Through the course of this coming week the subtropical ridge over
the Gulf of Mexico will slowly retrograde toward the West; which
will ease up a bit over the Southeast U.S. A closed low will
slowly sink southward through California with minimal eastward
progression due to the westward ridge expansion. This will promote
a slow moving cold front through the Pacific Northwest and Great
Basin regions. As northern stream energy periodically encounters a
persistent upper low in the vicinity of Hudson Bay, the energy
will amplify in the broad cyclonic flow with shortwaves digging
into the north-central and northeastern U.S.
The deterministic models had a decent handle on the pattern
progression for the first couple of days of the extended forecast
then quickly increased their spread, especially across the East.
The ensemble means were an improvement over the deterministic
solutions for days 5 and beyond. Therefore, the initial starting
point for this issuance was 00Z ECWMF, 00Z GFS and the 06 FV3 with
some inclusion of the 00Z NAEFS, GEFS and ECENS. Weighting of the
means increased while the deterministic decreased June 2nd onward.
These continues to be a signal within the models depicting the
northern stream ridge axis shifting eastward to the Northern
Plains/Midwest, which would allow stronger height falls across the
Pacific Northwest. Meanwhile, the subtropical ridge should
gradually retrograde to the western Gulf of Mexico, keeping a warm
and moist air mass feeding northward into the south central
states. Leading shortwave energy crossing the northern Rockies Sun
should bring a low pressure system into south central Canada by
early next week with the associated frontal system moving across
the Northern Plains and Midwest.
...Weather Highlights and Hazards...
Areas of showers and thunderstorms with locally heavy rainfall are
possible across portion of the Southern and Central Plains Fri-Sat
north of a weakening surface front along the Rio Grande Valley.
Showers and thunderstorms may become more widespread across these
areas Sun-Tue, with continued heavy rain potential, as another
cold front arrives from the north, providing additional
focus/enhancement of convection. Farther west, periodic showers
are expected from the Great Basin to the central/northern Rockies
as a couple weak southern stream shortwaves traverse the region.
This activity should be a bit more widespread Fri-Sat before
becoming more sparse Sun-Tue as the most significant shortwave
energy moves east and heights gradually rise across the region.
Temperatures across much of the Southeast are expected to continue
being above average for early June. Daily maximums are forecast to
be 5 to 10 deg F above average across this region into early next
week. Farther west, the Pacific Northwest will initially be quite
warm, with highs expected to be 10 to 15 deg above average with
the upper ridge in the vicinity. These temperatures should
moderate slightly by early next week, but above average
temperatures are expected to continue as northern stream shortwave
energy fails to lower heights substantially across the region.
Campbell
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