808
FXUS02 KWBC 070704
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
304 AM EDT Fri Jun 7 2024

Valid 12Z Mon Jun 10 2024 - 12Z Fri Jun 14 2024

...Hot temperatures for the West/Southwest plod into next week...


...Overview...

Into early next week, upper troughing is forecast for the eastern
U.S., which may get renewed into the middle of next week with
another shortwave. Periods of upper ridging are likely for much of
the West/Southwest into the central U.S., though could be
disrupted by shortwave energies at times. Hot temperatures will
continue across the West/Southwest during the medium range period,
possibly moderated a bit compared to the short range. A front
should focus moisture near the Rockies early next week, causing
showers and storms there and farther east across the U.S. southern
tier, but particularly for the southern Plains Monday. Rounds of
rain and storms are also possible in highly uncertain flow across
the Eastern Seaboard next week, but there is an inherent stronger
threat signal for a multi-day wet period with some heavy rainfall
potential into the Florida Peninsula starting Tuesday-Wednesday.


...Guidance/Predictability Assessment...

It remains the case that there remains some agreement on the large
scale pattern featuring a reloading Eastern U.S. trough and
Western U.S. ridging eventually working eastward, but plenty of
uncertainty in the details. Model run to run continuity regarding
a compact upper low over west-central Canada continues to pose a
significant problem. Models continue to flip-flop between whether
that energy and an associated weather focus is slow to be dislodged
over Canada before shifting generally east-southeastward along the
U.S. border versus sinking more robustly southeastward into the
north-central U.S./Midwest. So confidence is the details of this
remains very low. 12 and 18 UTC guidance overall trended toward the
latter, while latest 00 UTC guidance other than the GFS flipped
back towards the former as was the case with guidance a day ago.

Otherwise, there is uncertain timing of energies through the
Northwest into Monday and again as the main East Pacific trough
moves into the Coast late period, but forecast spread is improving.
This impacts how fast the upper ridge over the West moves out into
the Plains. Meanwhile...the Gulf Coast and Florida uncertainties remains
an issue mid to late next week regarding strength and presence of
upper troughing/shortwave energies to focus activity locally.

Given uncertainties in a pattern with below normal predictability
through medium range time scales, that extend uncharacteristically
from shorter ranges, the WPC product suite was mainly derived from
a blend of less detailed, but best compatible 12 UTC GEFS/ECMWF
ensemble means. The means bareky hinted at continuity change
without placing stock in depiction of flip-flopping flow embedded
systems that offered very minimal individual guidance signals.

...Weather/Hazards Highlights...

Ample pooled moisture and instability with a wavy front that will
tend to stall from the central Rockies to southern High Plains and
vicinity may produce periods with heavy convection with potential
for heavy rain rates, so a Marginal Risk area was delineated for
Day 4/Monday. A multi-day period favorable for some heavy rains is
then possible to develop across the Florida Peninsula starting
Tuesday as well above moisture pools along the stalling front with
some aid from weak upper level impulses/energy. Accordingly, a WPC
Day5/Tuesday ERO introduces a Marginal Threat area.

The mean ridge in the West/Southwest will continue to cause much
warmer than average temperatures, but seemingly not quite as hot as
in the short range period. The highest temperature anomalies of
10-20F above normal are forecast for the Great Basin, warming a bit
and expanding eastward as the week progresses into the northern
Rockies and Plains. Temperatures will also rise a few degrees in
the Desert Southwest to bring some temperatures back above 110F.

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 forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

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/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw







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