Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
438 PM EDT Tue Jun 25 2019
Valid 12Z Fri Jun 28 2019 - 12Z Tue Jul 02 2019
...Overview and Guidance/Predictability Assessment...
An initially deep closed upper low over the Pacific Northwest is
forecast to shear apart and send most of its energy into British
Columbia Friday through Saturday before remnant energy rounds a
deep ridge up the central CONUS and Canadian Prairies this
weekend. Meanwhile a trough will persist over the Pacific
Northwest into Sunday. Global guidance diverges with the Pacific
Northwest trough on Sunday with the 00Z NAEFS and its
deterministic components shifting the trough/closed mid-level low
farther west offshore while the 00Z ECMWF/ECENS maintains a trough
along the Pacific Northwest coast into the middle of next week.
Excellent agreement with deterministic solutions resulted in a
general model blend into Sunday. Starting on Sunday, a preference
was for the 00Z ECENS over the 00Z NAEFS given preferences to a
stronger trough over the Pacific Northwest (which agrees with a
teleconnection to persistent ridging over the Aleutians and
western Alaska).
There is good agreement on the upper ridge amplifying up High
Plains/Canadian Prairies into Saturday and the resultant deep low
ejecting southeast from Hudson Bay and crossing New England
Sunday. Global guidance again diverges at this time with the
00Z/06Z GFS maintaining a closed low off the New England coast
early next week while the 00Z ECMWF has an open trough with
similar position. A preference for this weaker trough off the
northeast also warranted inclusion of more 00Z ECENS than 00Z
NAEFS starting on Sunday.
Along the Gulf Coast, an inverted trough will drift west from the
western Gulf of Mexico Friday and stall over Texas through the
weekend.
...Weather Highlights/Threats...
The amplified upper low and lingering troughing will favor cooler
than average temperatures in most of the West (especially Pacific
Northwest into the Great Basin/Intermountain West) and scattered
rain/storms with some very high elevation snow in the Cascades
Friday into Saturday. Temperatures initially 5-15 deg F below
average should moderate some, but remain below normal as the
trough persists in the wake of the closed low. Temperatures in the
northern Plains/Upper Midwest will be 5-10 deg F above average
(80s to mid 90s), but with a daily risk of showers/storms with
locally heavy downpours in the vicinity of a warm front trough
Saturday and a persistent surface trough/stationary front Sunday
to Tuesday. The Northeast will see cooler temperatures
showers/thunderstorms this weekend followed and a drier air mass
next week as a front and low pressure sinks through the region.
The Southeast and lower MS Valley/Gulf Coast region will see a
daily chance of showers/storms in typical summertime fashion that
may be enhanced via the upper trough as it moves westward and
lower-level moisture increases from the Gulf.
Jackson
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
Hazards:
- Flooding possible across portions of the Central Plains and the
Middle Mississippi Valley.
- Flooding occurring or imminent across portions of the
Central/Southern Plains, the Middle/Lower Mississippi Valley, and
the Ohio Valley.
- Flooding likely across portions of the Central Plains and the
Middle Mississippi Valley.
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