Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
241 AM EDT Sat Jun 22 2019
Valid 12Z Tue Jun 25 2019 - 12Z Sat Jun 29 2019
...Overview...
An upper low is forecast to slowly rotate into Washington next
week as upper ridging expands over the High Plains. To the east, a
lead system will lift northeastward through New England as its
cold front stalls and then dissipates over the Southeast. Upper
ridging initially over the Gulf of Mexico will be replaced by an
inverted upper trough by next Fri/Sat.
...Guidance/Predictability Assessment...
A blend of the deterministic 12Z GFS/ECMWF/Canadian and 18Z GFS
offered a good starting point for the Tue-Thu forecast. Solutions
continue to converge with the lead system exiting the Great
Lakes/Northeast as the UKMET was the only one displaced from the
otherwise good consensus. In the Pacific Northwest, upstream
differences over Alaska have essentially vanished and a consensus
approach served well as the upper low wobbles into Washington next
Thursday or so before turning northeastward into British Columbia.
Trend toward more ensemble mean weighting acted to maintain good
continuity. Farther east, a trough may wrap around the
initial/lead system by next Fri/Sat into the Northeast in an
otherwise low-amplitude flow. To the south, the GFS-based guidance
continues to be a bit more defined with the upper trough near the
Gulf Coast than the ECMWF-based guidance.
...Weather Highlights/Threats...
Much of the West will see below normal temperatures on the order
of 5-10 deg F under the approaching upper trough. Contrastingly,
areas from the High Plains to the Northeast will see near to above
normal temperatures (up to about +5 to +10 deg F anomalies) from
especially Wed onward. Southern Plains to the Southeast will see
90s most days with a sprinkling of showers/storms during the
afternoons, enhanced initially by the weak front and then later by
the upper trough.
Precipitation will be quite scattered in nature over the
East/South due to a lack of concentrated forcing and deep
moisture. In the Pacific Northwest, the upper low will bring in
showers (and some very high elevation snow) that will gradually
expand over the northern Plains to the Upper Midwest later in the
week. Along the Gulf Coast, there is potential for locally heavy
rain depending on the details of the upper trough. Otherwise,
typical diurnally-driven storms will be common. The Southwest will
stay dry as the upper high settles near the AZ/NM border.
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