Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
231 AM EDT Fri Jun 21 2019
Valid 12Z Mon Jun 24 2019 - 12Z Fri Jun 28 2019
...Overview...
Troughing will continue to be favored in the Pacific Northwest
next week as an upper low slowly sinks southeastward then
eastward. To the east, a lead system will lift northeastward
through the Great Lakes as heights rise in its wake. Upper ridging
is forecast to slide westward across the Gulf of Mexico and into
the Mexican plateau and far western Texas/southern New Mexico.
...Guidance/Predictability Assessment...
Deterministic blend of the latest 12Z/18Z guidance offered a good
starting point for the Mon/Tue forecast. Differences in timing
with the eastern system (slower ECMWF/Canadian vs quicker
GFS/UKMET) were smoothed out given wavering trends in recent model
cycles. By Tue into Wed, models/ensembles show increasing
divergence in solutions off the west coast, stemming from how
mid-level energy over Alaska on Monday either lingers over the
high latitudes or drops down on the southwest side of the lead
upper low off Washington on Tue/Wed. In these highly uncertain
flow regimes with divergent solutions, agreement among the models
is rather useless and often fleeting. Rather than getting caught
up with the latest deterministic guidance, opted to rely more on
the ensemble means which aligned well with continuity in order to
prevent undesirable waffling in the forecast. The
GFS/ECMWF/Canadian solutions were all plausible yet quite
different, but the eventual outcome may very well be "none of the
above." Farther east, ensembles were in good agreement on moving
the weak trough eastward along with its surface cold front.
...Weather Highlights/Threats...
Much of the West from WA/OR/NorCal eastward through the Great
Basin will see below normal temperatures on the order of 5-15 deg
F. Areas from the High Plains to the Northeast will see near to
above normal temperatures (up to about +5 to +10 deg F anomalies)
but generally not near record maxes. Cold front will not bring in
much colder air to the East but rather a bit drier (briefly).
Southern Plains to the Southeast will see 90s most days with a
sprinkling of showers/storms during the afternoons.
Precipitation forcing will be best on Monday along/ahead of the
cold front in the Corn Belt/Midwest and mid/lower-Mississippi
Valley. Scattered showers/storms will push eastward with the front
but generally with less coverage Tue/Wed. In the West, upper low
will bring in some showers (and still some very high elevation
snow) that will gradually expand over the Plains to the Upper
Midwest later in the week as the trough and cold front move
eastward.
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