Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1204 PM EDT Wed Jul 04 2018
Valid 12Z Sat Jul 07 2018 - 12Z Wed Jul 11 2018
...Weather threats/highlights....
An upper high will continue to dominate the lower 48 this coming
weekend into the middle of next week. Troughs over the Northwest
and Northeast flatten with time as a more zonal flow takes shape
along the US/Canadian border as heights become above average coast
to coast. A moderating front in the east will sink into the
Southeast this weekend and dissipate next week as western North
American fronts shift downstream across the northern plains, Upper
Midwest/Great Lakes and Northeast along with thunderstorm focus
and local severe storm threat as per SPC.
The Southwest offers potential for record warmth in this pattern,
especially this Saturday in southern California where maximum
temperatures in the 90s are likely to the coast and well into the
100s inland. Record high minimum temperatures also threaten
southern California to southern Arizona this weekend, including
Phoenix.
...Guidance evaluation/preferences...
The 06 UTC GFS/GEFS, 00 UTC ECMWF, and 00 UTC NAEFS/ECMWF/Canadian
ensembles cluster reasonably well with flow evolution days 3-7.
The biggest guidance continuity change compared to yesterday is
that latest guidance is now more amplified and less progressive
with downstream shortwave energy ejection from a mean position off
the Pacific Northwest. This adjustment seems to make sense
considering the track of a deepened extratropical low associated
with the remnants of current west Pacific tropical storm Prapiroon
toward Alaska would support this trend to amplify flow downstream
into the CONUS.
Fracasso/Schichtel
WPC medium range 500 mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indexes are found at:
http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
http://www.wpc.ncep.noaa.gov/heat_index.shtml