Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
227 AM EDT Fri Jul 02 2021
Valid 12Z Mon Jul 05 2021 - 12Z Fri Jul 09 2021
...Threat of heavy rain for Florida and the Southeast Coast early
to middle next week as Tropical Storm Elsa potentially impacts the
region...
...Threat of repeating heavy rain over southern Texas as low
pressure persists through much of next week...
...Overview...
A summer-like pattern sets up for next week as a strong upper
ridge sets up over the Desert Southwest to the Four Corners
states, a weak upper trough/low develops over Texas move across
the south-central CONUS, while the main jet stream/westerlies
meander over the northern U.S. and southern Canada. Additionally,
Tropical Storm Elsa has the potential to cross Florida and move up
Southeast Coast early to midweek.
...Guidance/Predictability Evaluation...
Guidance is pretty agreeable with the overall pattern (with the
main exception for the track/timing/strength of Elsa) through
midweek. A deterministic general model blend was able to be used
for Monday and Tuesday. The 12Z CMC was removed by late Tuesday as
it had a stronger upper low in the Eastern Pacific offshore of the
Pacific Northwest with a stronger trough over the south-central
CONUS resulting in a stronger and faster Elsa. There were some
minor differences with northern stream shortwave troughs, which
were muted a bit by transitioning to a blend favoring more of the
agreeable GEFS and EC ensemble means later next week.
Guidance is quite variable in terms of the track and strength of
Elsa. The 12Z ECMWF continues to weaken the system by Hispaniola.
Meanwhile, the 18Z/00Z GFS take a stronger Elsa into the eastern
Gulf of Mexico before crossing the Florida peninsula and moving up
the Southeast Coast. Run-to-run timing differences are noted with
the 00Z run now slower than the 18Z. The 12Z and 00Z CMC remain
the fastest solution with a stronger system through Florida like
the GFS - the 00Z CMC has shifted farther east than the 12Z. The
00Z UKMET remains similar to the GFS, with the system entering the
eastern Gulf of Mexico on Tuesday, but the UKMET continues to
weaken the system before making any US landfall. Thus, uncertainty
remains rather high with Elsa though a decent heavy rain threat is
present for Florida and possibly the Southeast Coast. The WPC QPF
forecast followed the NHC track, which remains closer to the
recent GFS and UKMET.
...Weather Highlights/Hazards...
An upper low/trough sets up over Texas making for a heavy rain
threat there each day of the next work week with multi-inch totals
likely. Farther west, late-day monsoonal type showers and
thunderstorms are likely Monday into Wednesday over the
Central/Southern Rockies. Periods of rain are forecast along and
ahead of a front from the north-central to northeastern CONUS.
Heavy rainfall, flooding, and high winds are potential threats
where Elsa tracks. Timing and strength of Else have considerable
uncertainty, but there is a heavy rain threat for portions of the
Florida Peninsula Tuesday and across the Georgia and Carolina
coast Wednesday with Elsa.
The heat wave now looks to persist over the western CONUS through
next week as ridging lingers, restrengthens with max temperature
anomalies of 10 to 20 degrees above normal for the Northwest with
some daily record high temperatures mostly in the Great Basin.
Temperatures will generally be a few degrees cooler than average
in the south-central U.S./Texas through the week with cloudiness
and rain from the persistent upper level disturbance there.
Jackson
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