Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 AM EDT Fri Jun 18 2021
Valid 12Z Mon Jun 21 2021 - 12Z Fri Jun 25 2021
...High Heat over the West spreads to the Plains next week...
...Wet remnants of "Three" exits Carolinas Monday to lift off East
Coast...
...Trailing frontal heavy rains across the South to the East early
next week...
...Guidance/Predictability Evaluation...
Recent GFS/ECMWF and GEFS/ECMWF ensemble mean runs for days 3-7
are mainly well clustered and along with the overall
representative National Blend of Models seem to act as a
reasonable forecast base in a pattern with above normal forecast
predictability.
...Weather Highlights/Hazards...
Ongoing record-breaking and dangerous heat over the
Southwest/California may slowly moderate next week, but it will
still be hot. High heat is also expected for the Northwest and
Great Basin and will also spread into the Plains.
Potential Tropical Cyclone "Three" is forecast by the NHC to
develop and reach the central Gulf Coast Saturday and track across
the South/Southeast this weekend. By Monday, the moist remnant
system and heavy rains are subsequently expected to move offshore
the Carolinas before lifting off the East Coast as mainly a
maritime threat. Early next week upper support, frontal approach
and Gulf moisture/instability return in the wake of "Three" will
support periods of strong convection with heavy downpours across
the already wet South that would lead to additional runoff issues,
especially with lead training. Generally progressive frontal
focusing rains will meanwhile also spread through the Ohio Valley,
Appalachians and the Eastern Seaboard, lingering over the
Southeast/Florida midweek with the trailing front.
Upstream, additional digging upper energies and return frontal
support may combine to favor a moderate convective rain focus from
the eastern Plains and north-central Mid-Mississippi
Valley/Midwest later next week.
Schichtel
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook 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