Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
233 AM 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 is forecast to slowly but
steadily move through the Pacific Northwest and then into British
Columbia late this week and weekend before weakening. Upper
ridging will build downstream over the High Plains into the
western Great Lakes while troughing in eastern Canada (Hudson Bay)
will dig into the Northeast over the weekend. Along the Gulf
Coast, an inverted trough will develop and move westward as an
upper high settles into AZ/NM. The latest deterministic models
offer a reasonably well-clustered starting point for the Fri-Sun
period. Thereafter, incorporated the GEFS/ECMWF ensemble means
which smoothed out smaller-scale timing and amplitude differences
for the lower 48.
...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 on Friday.
Temperatures initially 5-15 deg F below average will moderate back
toward typical late-June values by next week as heights rise.
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. The Northeast will see warm/hot temperatures Fri/Sat
be replaced by cooler temperatures and a drier air mass by next
week as a front 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, but that may be
enhanced via the upper trough as it moves westward and lower-level
moisture increases from the Gulf.
Fracasso
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