Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1200 PM EDT Sun Jul 28 2019
Valid 12Z Wed Jul 31 2019 - 12Z Sun Aug 04 2019
...Overview and Guidance/Predictability Assessment...
The medium range North American upper flow pattern will be driven
by a closed high over the Four Corners as well as upstream over
southern Alaska. This favors positively-tilted troughing over the
northeastern Pacific into WA/OR and also downstream over the
east-central U.S. underneath more dynamic eastern Canadian
troughing. Models/ensembles have struggled with Pacific flow
including the timing/track of a pair of midweek then later week
systems. Confidence remains low with these systems, but about
average elsewhere. A composite blend of the 06 UTC GFS and 00 UTC
ECMWF/UKMET seems to offer a decent flow/system depiction Wed-Fri.
opted for a blend of the compatable 06 UTC GEFS mean and 00 UTC
ECMWF ensemble mean along with WPC continuity through next weekend
amid growing forecast spread with embedded system amplitude,
timing and local convective/MCS focus.
...Weather Highlights/Threats...
Below average temperatures in AZ/UT due to monsoonal moisture (and
in increase in clouds/showers/storms) will moderate a bit with
time as the upper high drifts just enough eastward to focus
rainfall over CO/NM next weekend. Overtop, coastal Washington may
see an increased rain chance into later week on the uncertain edge
of lifting Pacific energies. Downstream, a wavy frontal boundary
draped over the east-central states will be a focus for convective
rainfall including some locally heavier downpours/runoff issues
through the period as fueled by pooled moisture and instability
under the mean trough aloft and a series of digging/passing
impulses aloft. East of Florida, an emerging tropical wave may
bring increased rainfall to the Bahamas and perhaps into eastern
North Carolina next weekend.
Fracasso/Schichtel
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