Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1159 AM EDT Mon Jul 09 2018

Valid 12Z Thu Jul 12 2018 - 12Z Mon Jul 16 2018

...Overview...

Upper ridging will continue to dominate the lower 48 later this
week into next week. Current tropical storm Chris will lift
northeastward away from New England into southeastern Canada
Thursday/Friday with a trailing upper trough helping to keep it
offshore. Another shortwave will dig through southwestern Canada
Fri/Sat and then head eastward across the Canadian prairies Sunday
before lifting toward Hudson Bay next Monday as the 594 dm upper
high over the middle Mississippi Valley meanders in place. This
will allow a frontal boundary to dip into the northern Rockies and
High Plains/Upper Midwest this weekend but slow as it sinks
southeastward into the Midwest.

...Guidance evaluation and preferences...

Latest 00Z/06Z guidance offered a good starting point and a
blended solution was implored to start. The 00Z UKMET remained a
bit slower with Chris off the East Coast and deeper with the
trailing upper trough but otherwise was close to the deterministic
consensus for the rest of the CONUS/southern Canada. By Sun/Mon
next week, the GFS runs were stronger with the trough over
northeastern Montana into North Dakota than the ensembles (even
deeper than the deepest ensemble member from the 90-member
GEFS/ECMWF/Canadian ensembles) but the 00Z ECMWF/Canadian may have
been too far northeast per the ensemble consensus. A blend toward
the ensembles was used for days 6-7 (Sun/Mon) given uncertainty in
the upper trough and sfc front strength/speed.


...Weather highlights...

A cold front will bring showers/storms to the northern Plains into
the Great Lakes Thu/Fri but more isolated coverage Sat/Sun in the
Northeast with decreasing upper support. The next front will move
out of Canada this weekend with scattered showers and
thunderstorms along/ahead of its boundary and cooler air in its
wake. Temperatures will be below average on Sunday over Montana
then southeastward to Minnesota/Nebraska on Monday. Ahead of the
front, temperatures will be about 5-10 degrees above average (80s
and many 90s). Temperatures initially near 100 over portions of
the interior Pacific Northwest/Great Basin will cool a bit this
weekend.

From the southeastern U.S. westward along the Gulf Coast, a
dissipating front will keep a chance of showers and thunderstorms
in the vicinity through the weekend. Monsoonal moisture will
linger across the Four Corners area where locally heavy downpours
will be possible through early next week. Temperatures will
generally be near to below average in the Southwest under limited
solar insolation and a daily chance of showers/storms.


Fracasso/Kong


WPC medium range 500 mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indexes are found at:

<a href="http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif"><u>http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif</u></a>
<a href="http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif"><u>http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif</u></a>
<a href="http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html"><u>http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html</u></a>
<a href="http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml"><u>http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml</u></a>
<a href="http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4"><u>http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4</u></a>
http://www.wpc.ncep.noaa.gov/heat_index.shtml