814
FXUS02 KWBC 291859
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 PM EDT Sat Jun 29 2024

Valid 12Z Tue Jul 02 2024 - 12Z Sat Jul 06 2024


...Hazardous heat over the South next week spreads to parts of the
East/Southeast and California/Southwest into the Holiday period...

...Heavy convective rainfall focus for the Midwest next week...


...Pattern Overview...

An established pattern will generally continue as multiple
shortwave passages across the northern tier of the nation will fuel
scattered to numerous showers and storms for much of next week,
particularly across the Midwest and portions of the Central Plains
where the heaviest rainfall is likely to be midweek. Heat and
humidity will continue to make weather headlines across much of the
southern tier states as a strong ridge of high pressure aloft
governs the overall weather pattern, and heat also expands across
much of California and the lower elevations of Arizona and southern
Nevada as the upper ridge builds across the West by the end of the
forecast period. There will also be copious moisture in place
across much of the Southern Rockies that will fuel daily storms.

...Guidance/Predictability Assessment...

Model and ensemble forecast spread remains lower than normal
through medium range time scales in a pattern with above average
predictability, albeit still with standard smaller scale weather
feature uncertainties that tend to be muted by a guidance blending
process. The WPC product suite was primarily derived for the
Tuesday- Thursday/July 4th timeframe from a blend of well clustered
guidance of the 06 UTC GFS and 00 UTC ECMWF/UKMET/Canadian along
with the generally compatible 13 UTC National Blend of Models (NBM)
and WPC continuity. Opted to switch the favored blend to best
clustered guidance from the GFS/ECMWF and GEFS/ECMWF ensemble means
along with the NBM for later next week amid slowly growing
variances at these longer time frames.

...Weather/Hazards Highlights...

Widespread showers and storms are expected to be ongoing across
portions of the Upper Midwest and western Great Lakes region on
Tuesday ahead of a frontal boundary and an upper level impulse
moving through the region. Locally heavy convective downpours may
fall on saturated grounds in some cases, which would be an
aggravating factor when it comes to flooding potential. Therefore,
the Slight Risk remains valid for the Day 4 ERO for this region.
Marginal and Slight Risk ERO threat areas also remain for the Day
5 outlook Wednesday as the signal for a main axis of heavy
convection drops southward to include eastern Kansas, much of
Missouri, and into central Illinois. Activity should remain broadly
robust over the Midwest through the Fourth leading to possibly
ample runoff issues, but focus may gradually ease and slowly shift
southward and eastward across much of the central and eastern U.S.
late next week/weekend with less certain flow/frontal progression.

Monsoonal flow into the Southwest states will continue the daily
threat for showers and storms through much of the period. Marginal
risks remain in place across parts of Arizona and New Mexico for
both the Day 4 and 5 EROs, with the potential for upgrades to a
Slight Risk in subsequent updates during the short range forecast
period. There may be some southern suppression of this moisture
going into the end of the week and confine the greatest coverage of
convection across southeast Arizona and southern New Mexico.

It will continue to remain hot and humid across the Southern U.S.
for much of next week, with the hottest conditions centered across
Texas and Oklahoma where triple digit high temperatures are likely.
Some of this heat likely reaches the Mid-Atlantic region after a
brief cool-down by the end of the week with highs returning to the
90s amid increasing humidity levels. It will also be getting
hotter for the inland lower elevations of California and into the
Arizona Deserts with widespread 100-110 degree readings likely, and
locally higher for the normally warmer locations.

Hamrick/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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