Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1225 AM EDT Fri Jun 15 2018
Valid 12Z Mon Jun 18 2018 - 12Z Fri Jun 22 2018
...Heavy rains possible for portions of the northwestern Gulf
Coast and portions of the central/northern Rockies/plains...
...Hot/humid for portions of the Midwest to the Mid-Atlantic and
Southeast early next week...
...Pattern overview and model/guidance assessment/preferences...
A stuck upper low over the Great Basin on Monday will slowly
weaken as ridging in the east gives way to cyclonic flow through
the Great Lakes. To the south, a weakness aloft and a tropical
wave at the surface will wring out several inches of rain over the
northwest Gulf Coast region during the week. The latest GFS/ECMWF
and their ensemble means were in good agreement through the period
and a blend of them served well as a starting point. This will
take a surface cold front slowly southward out of the Great Lakes
on Monday into the Mid-Atlantic by Wednesday but linger back to
the west through the southern Plains into the Rockies. The upper
low in the west will help draw in moisture from weakening tropical
storm Bud through the Rockies into Wyoming/Idaho and southern
Montana.
...Weather highlights/hazards...
Locally heavy (and regionally modest) rain is probably for the
northwestern Gulf Coast as the broad trough/area of disturbed
weather moves onshore early in the period. Multi-inch rainfall
totals appear possible, focused over portions of southeastern
Texas and southwestern Louisiana. To the northwest, the upper low
and moisture from (by then) the remnants of Bud will combine to
produce several days of wet weather for the central/northern
Rockies (with below average max temperatures). Totals of 1-2" may
be common for the 5-day total.
Temperatures in the east will be well above average (+10 to +20F)
to start the medium range (Monday) from the Midwest to the
Northeast/Mid-Atlantic with readings well into the 80s/north and
90s/south and approaching 100 in the typical hot spots (near STL
and RIC/RDU). Many daily record maxes will likely be tied/broken
along the I-95 corridor. With dew points into the upper 60s
(north) and low to mid 70s (south), heat indices will be over 100F
and close to 110F for some areas. The Pacific Northwest will also
see well above average temperatures (especially inland) as they
will be located to the northwest of the upper low and coincident
with ridging moving out of the northeast Pacific. Temperatures
will rise into the 70s/80s west of the Cascades and 90s in the
interior of Washington/Oregon.
Fracasso
WPC medium range forecasts of 500 mb heights, surface systems,
weather grids, quantitative precipitation, and winter weather
outlook probabilities can be 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