Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
220 AM EDT Wed Jul 31 2019
Valid 12Z Sat Aug 03 2019 - 12Z Wed Aug 07 2019
...Overview and Guidance/Predictability Assessment...
Strong upper ridging over the Gulf of Alaska favors troughing
along the Pacific Northwest and through the Great Lakes with
weakening ridging over the Four Corners region. The
model/ensembles mostly agree on the longwave pattern and a blend
of the deterministic models sufficed for the weekend period. This
takes a system through central Canada with its attendant fronts
astride the central northern tier into the southern Mid-Atlantic.
Thereafter, the 18Z GFS and 12Z ECMWF clustered well enough with
their ensemble means so that a consensus blend sufficed as a
starting point Mon-Tue as the Canadian low progressed into Quebec
and the cold front enters the Northeast. By next Wed, spread
increases with the evolution/track of the eastern system as recent
GFS runs were well north or south of the ECMWF, which was closer
to the ensemble mean consensus and was the preferred location.
Over Florida, a tropical wave or surface trough will lift
northward along then away from the Space/Treasure Coast this
weekend and into the stationary boundary to the north.
...Weather Highlights/Threats...
Monsoonal moisture will focus rainfall mostly over New Mexico
Saturday then into AZ/UT/CO next week. Leftover MCS (uncertain
details) may sink through Arkansas early Saturday as it rounds the
ridge. Elsewhere, rainfall will follow the front in the north and
largely pop up in the afternoon in the Southeast, perhaps enhanced
over eastern Florida into the coastal Carolinas as the tropical
wave dissipates.
Temperatures will be a bit cooler than average over the central
states with higher chances of rainfall and clouds. Milder than
average temperatures are expected over the Great Lakes and
Northeast ahead of the northern tier system. Elsewhere,
temperatures will be within a few degrees of typical early August
values during the day and near/above average for overnight mins in
much of the West.
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