Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
254 AM EDT Sun Jul 28 2019
Valid 12Z Wed Jul 31 2019 - 12Z Sun Aug 04 2019
...Overview and Guidance/Predictability Assessment...
Upper 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 again over the eastern states. The models/ensembles have
really struggled with the Pacific flow including the timing/track
of a pair of systems Wed and again around Friday. The 12Z/18Z
guidance split between quicker (ECMWF and most ensembles) and
slower (deterministic GFS/Canadian/UKMET). Ensemble trend was
decidedly quicker but was odd that only the ECMWF followed suit.
Glance at the 00Z guidance showed a trend quicker but still not as
quick as the ECMWF. However, this fit well with the blend using
the pre-00Z guidance; namely, the ensemble mean consensus. Used a
50/50 GEFS/ECENS mean consensus to round out the forecast which
allows some shortwave energy to crest atop the upper high through
Canada and maintain the trough in the east (albeit with above
average heights). Confidence was low in the Northwest but about
average elsewhere.
...Weather Highlights/Threats...
Temperatures below average 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. Frontal boundary in the east
will be a focus for convective rainfall including some locally
heavier downpours/runoff issues through the period, but drifting
eastward/southward day by day. East of Florida, a trough may bring
a somewhat expanded area of rainfall through the Bahamas and
perhaps into eastern North Carolina next weekend just south of the
front. Finally, coastal Washington will see an increased chance of
rain later in the week but this will be dependent on details yet
to be determined.
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