Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
244 AM EDT Thu Jul 05 2018
Valid 12Z Sun Jul 08 2018 - 12Z Thu Jul 12 2018
...Weather threats/highlights....
An upper high will continue to dominate the lower 48 next week.
Troughs over the Northwest and Northeast flatten with time as a
more zonal flow takes shape along the US/Canadian border. Heights
will become above average coast to coast which supports near to
above average temperatures over most areas outside the southern
tier. A moderating front in the east will 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 will see enhanced monsoonal moisture around the upper
high realized as precipitation initially over the higher terrain
and then into some of the lower deserts.
...Guidance evaluation/preferences...
Models and ensembles remain in good agreement overall, but with a
noticeable exception over the Pacific Northwest. The GEFS and
ECMWF ensembles have trended away from each other in their 12Z
runs early in the week with an approaching trough just ahead of
the remnants of former tropical system Prapiroon. With such a
large disparity and sudden change, opted to take a middle ground
near the 12Z EWCMF (with the 18Z GFS much slower and closed off)
and somewhat like the 12Z GFS. Over the rest of the lower 48, the
upper high may attempt to push eastward again next Tue-Thu but the
ensembles differ on how much troughing to allow through the
Northeast. Again split the difference given the upstream
uncertainty.
Fracasso
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