Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
222 AM EDT Mon Jun 24 2019
Valid 12Z Thu Jun 27 2019 - 12Z Mon Jul 01 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 later this week and weekend. 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 next weekend. Along the Gulf Coast, an inverted trough
develops will move westward as an upper high settles into AZ/NM.
The latest deterministic models offer a reasonably well-clustered
starting point for the Thu-Sat 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. Temperatures
initially 5-15 deg F below average will moderate back toward
typical late-June values by late next weekend as heights rise.
Temperatures in the northern Plains/Upper Midwest will be 5-10 deg
F above average (80s to low or even 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 cooler
temperatures by Sunday 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 as the upper trough moves westward as lower level
moisture slowly 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