WPC Medium Range Archive
Medium Range Products Valid On:
(Day 7 PMDEPD: Valid 06/13/2019 to 06/17/2019)
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
334 PM EDT Mon Jun 10 2019
Valid 12Z Thu Jun 13 2019 - 12Z Mon Jun 17 2019
...Overview and Guidance/Predictability Assessment...
A fairly amplified trough with embedded shortwave energy trough
will be over the northeast/eastern U.S. through the extended
period, although steadily becoming more shallow with time. Model
consensus has improved with the last two runs in regards to
amplitude, placement and timing- at least for earlier periods. The
spread increases Saturday afternoon particularly over the
north-central region likely in response to the western U.S.
transitioning to a less amplified pattern. A trough over the Gulf
of Alaska/north Pacific will be deepening as it progresses toward
the West Coast. The expected transition of the pattern to a lower
amplitude regime with embedded medium to smaller scale features
(having low predictability) continues to cause significant
difficulty in resolving important details.
For the East, the key uncertainty remains with the energy that
starts the period early Thu in the vicinity of northern
Ontario/southern shore of Hudson Bay. Individual solutions are
too varied to describe in detail but essentially break down into
one of two scenarios, the feature either remaining over Canada or
else at some point dropping farther south and brushing the
northeastern quadrant of the Lower 48. The path of this energy
will dictate the speed and how far south the front will extend.
Multiple shortwaves tracking across the West and Plains will
increase the likelihood for a pattern that could support heavy
rainfall potential over parts of the south-central Plains and
extending east/northeast. This section of the country continues to
have historic river flooding and are highly sensitive to any
The guidance continues to suggest a somewhat weaker and faster
trend for this energy in the days 3-5 Thu-Sat time frame. Once
again, the GFS solution becomes the deepest over the Southwest
Sunday and Monday, which deviates from the model consensus. This
low confidence forecast was comprised of the 00Z ECMWF, 00/06 GFS,
06Z FV3 and increasing weight of the 06 GEFS and 00Z ECMWF/NAEFS
means by days 6-7 Sun-Mon. This provided more subtle adjustments
from continuity than following any particular model scenario.
...Sensible Weather Highlights/Threats...
The system affecting the Great Lakes/Northeast early in the period
will bring rainfall of varying intensity throughout Thursday.
Emerging consensus indicates highest totals may remain offshore
while system progression could limit rainfall accumulations as
well. Then the rainfall focus will shift westward as weak
shortwaves move into/through the West and emerge over the central
U.S. This energy may produce at least a modest surface
low/frontal system while southern Canada/northern U.S. flow east
of the Rockies could push a separate front southward. Expect
periods of showers/thunderstorms on multiple days over the
northern two-thirds of the West with best organization likely in
the northern-central Rockies. Farther east there is still
considerable uncertainty over specifics of surface features that
will serve to focus convection. However in principle guidance
over the past day has trended toward higher potential for heavy
rainfall within an area extending from the south-central High
Plains into the Ohio Valley. Some individual solutions display
such potential elsewhere as well. Currently the ensembles as a
whole focus the greatest probability of highest totals for the
five-day period over parts of Kansas/Oklahoma/Missouri/Arkansas.
Expect the Florida peninsula to be another favored area of
meaningful rainfall during the period.
Temperatures over the West should remain above normal though to a
lesser extreme than expected through Wed. Some scattered plus
10-15F anomalies for highs will be possible from extreme northern
California into the interior Northwest and extreme northern
Rockies while the West will see a broader expanse of plus 5-15F
anomalies for morning lows from late week into next Mon. Below
normal readings will prevail over much of the eastern half of the
country Thu-Fri. Then anticipate temperatures closer to normal
though perhaps averaging slightly below average overall.
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
- Heavy rain across portions of the Southern/Central Plains, the
Lower/Middle Mississippi Valley, the Tennessee Valley, and the
Ohio Valley, Thu-Mon, Jun 13-Jun 17.
- Flooding possible across portions of the Mid-Atlantic and the
- Flooding occurring or imminent across portions of the Plains,
the Mississippi Valley, the Great Lakes, the Southern
Appalachians, the Southeast, and the Ohio Valley.
- Flooding likely across portions of the Great Basin, the
Northern/Central Rockies, the Northern Plains, the Middle
Mississippi Valley, and the Southern Plains.
- Excessive heat across portions of the Southern Plains, Sat-Mon,
Jun 15-Jun 17.
- Much above normal temperatures across portions of California,
the Pacific Northwest, the Northern Rockies, and the Northern
Great Basin, Thu-Mon, Jun 13-Jun 17.
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at: