Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
109 AM EDT Thu Jun 20 2019
Valid 12Z Sun Jun 23 2019 - 12Z Thu Jun 27 2019
...Weather Highlights/Threats...
The persistent upper ridge over the southeast continues to advect
warm air east across the southern Mississippi Valley and the
Southeast/TN Valley/Oh Valley/Appalachians on Sunday, and
continuing into the Northeast early next week. Expect high warm
sector temperatures under this ridge, with most areas several
degrees above normal. Another area of warmer than normal
temperatures develops as the upper ridge build north across the
Plains, with anomalies as much as ten degrees above normal day 7
Thu 27 Jun in eastern MT and ND.
After initial cold in the high Plains, temperatures moderate early
next week.
the developing low in the northwest leads to a cooling trend next
week, with widespread temps several degrees below normal, focused
on northern CA day 6 Wed 26 Jun and day 7 Thu 27 Jun.
Forcing ahead of the trough crossing the Rockies this weekend
presents a threat of strong to severe/MCS convection and locally
heavy rains in areas with pooling moisture/instability. The
rainfall focus Sunday and Monday is forecast to be from eastern
Kansas and Oklahoma across the Mississippi Valley into the Great
Lakes and the Midwest.
On Tuesday 25 Jun /Wednesday 26 Jun the showers/storms are
expected to focus from east Texas across the Arklatex to the lower
MS Valley, Florida and the Northeast.
...Guidance/Predictability Assessment...
The WPC medium range product suite was derived from a blend of the
18z UTC GEFS and 12 UTC ECMWF ensemble mean guidance, with minimal
weighting on the operational GFS/ECMWF. The 18 UTC deterministic
GFS returned to its long term bias of moving the 500 mb wave out
of the central US faster than the ECMWF/Canadian and the ECMWF and
GEFS Means starting on Mon 24 June. This continues across the
Great Lakes Mon night-Tue. The 12z ECMWF had a different issue
with the same system, producing a more amplified 500 mb trough and
possible embedded closed low across the upper MS Valley Mon and
Great Lakes Tue that caused the ECMWF to be on the slow end of the
guidance envelope. Given most ECMWF and GEFS members cluster in
between the ECMWF and GFS, the preferred solution was weighted
heavily towards the means.
Next week, a new closed low develops and moves southeast from
offshore British Columbia into the Pacific northwest or adjacent
coastal waters by the middle of next week. This persistent and
slow moving circulation allows the deep layer ridge to rebuild
over TX and NM, and then extend north into the northern Plains.
There is less spread than normal for this consensus, lending the
situation to a consensus based approach.
Petersen
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