Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 PM EDT Tue Jul 23 2019
Valid 12Z Fri Jul 26 2019 - 12Z Tue Jul 30 2019
...Weather Highlights/Threats and Guidance/Predictability
Assessment...
Latest models still indicate that eastern US upper troughing will
gradually deamplify this weekend into early next week as a mid
level ridge builds across Florida. A weakening front in Florida
and into the Gulf of Mexico will remain a main focus for heavier
convection and rainfall, with return warm/moist advection early
next week allowing activity to move north across the lower MS
Valley and southeast.
A persistent feature in the upcoming pattern will be a closed high
over the Southwest. Expect daily scattered monsoonal convection
will work around the ridge over the southern Great
Basin/Rockies/High Plains in upper diffluent flow, and pockets of
above normal temperatures in the interior CA/OR across NV/ID/AZ.
Overtop, mid-level impulses and wavy surface fronts will traverse
the northern tier states from the Pacific Northwest eastward to
the Great Lakes. These will enhance moisture, instability and
periods of convection/MCS activity, especially from the n-central
U.S. into the Midwest/Great Lakes. Teleconnections from the
Southwest ridge corresponds to a trough from the Great Lakes to
the lower OH Valley, where rainfall probabilities increase.
Model/ensemble forecasts cluster well through the weekend, with
forecast spread increasing early next week. The WPC medium range
product suite was mainly derived from a blend of the 06 UTC GFS/00
UTC ECMWF days 3-5. A 06 UTC GEFS/00 UTC ECMWF ensemble mean blend
was used days 6-7 amid growing system variance and uncertainty.
This maintains max WPC continuity.
Schichtel
Hazards:
- Heavy rain across portions of the Middle Mississippi Valley, the
Lower Mississippi Valley, the
Great Lakes, and the Ohio Valley, Mon-Tue, Jul 29-Jul 30.
- Heavy rain across portions of the Middle Mississippi Valley, the
Great Lakes, and the Upper
Mississippi Valley, Sun, Jul 28.
- Flooding occurring or imminent across portions of the Central
Plains, the Middle Mississippi
Valley, the Lower Mississippi Valley, the Upper Mississippi
Valley, and the Northern Plains.
- Flooding likely across portions of the Middle Mississippi Valley.
- Excessive heat across portions of California and the Southwest,
Fri-Sun, Jul 26-Jul 28.
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