Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 PM EDT Sun Jun 8 2025

Valid 12Z Wed Jun 11 2025 - 12Z Sun Jun 15 2025


...Heavy rain and flash flood threat for the south-central U.S.
this week...


...Overview...

As the medium range period begins midweek, a front will be stalled
west to east across the southern tier and eventually lift
northward. The front will continue to provide focus for moderate to
heavy rainfall across portions of the southern Plains and
lower/middle Mississippi Valley. The multiple rounds of storms are
likely to cause flooding and flash flooding concerns. To the north,
a shortwave moving through the Northwest through the northern
Plains will bring showers and thunderstorms mid to late week. Then
rainfall should increase in coverage across the Ohio Valley into
the East late week into next weekend ahead of these combining
energies. Temperature-wise, the main warm anomalies should be in
the interior West underneath mean upper ridging.


...Guidance/Predictability Assessment...

Model guidance continues to show above average agreement on the
overall large scale pattern and evolution during the medium range
period. Was able to use a multi-model deterministic blend of 00/06Z
guidance early in the forecast period, and gradually increased the
proportion of ensemble means to half by Day 7.

The more difficult aspects of the forecast are the more variable
smaller scale details of shortwaves that impact the sensible
weather. Small model differences in southern stream
troughing/energy in the south-central U.S., along with model
difficulties in resolving convective evolution in the medium range
period, make the details of the rainfall forecast in the southern
Plains and vicinity uncertain and variable from cycle to cycle.
Verification shows that AI guidance, particularly the AIFS, tends
to be one of the best models with convective propagation. So leaned
more toward the AIFS (06Z version at the time, but other versions
look similar) through the Wednesday forecast for position of the
heaviest rainfall, but with increased rain totals. By later
Thursday the AIFS may be slightly east of consensus with the trough
though, so did not rely on it as much. The AI guidance like the
AIFS and GFS Graphcast was one of the main reasons that the EROs
gave some room on the eastern sides of the Slight and Marginal
Risks. Meanwhile in the West, one of the forecast challenges is
with shortwaves ahead of the primary eastern Pacific upper low
allowing for multiple rounds of fronts, so expect the fronts
forecast to continue to evolve. On the larger scale, the incoming
12Z guidance is coming in with the consolidated upper low farther
north toward Alaska while energy may split away on its southern
side compared to previous model cycles, so this trend will continue
to be monitored.


...Weather/Hazards Highlights...

A frontal boundary draped generally west to east across the South
will continue to provide focus for numerous showers and
thunderstorms through most of this week. Guidance continues to
converge on Texas and surrounding states as seeing multiple rounds
of heavy rain, with parts of this area (from northern Texas
northward) already primed for flooding with wet antecedent
conditions from recent rainfall. Thus Slight Risks remain in place
for much of Texas and into southern Oklahoma on Day 4 and 5 (valid
Wednesday and Thursday) and inching into the Ark-La-Tex Day 5 as
the primary convection moves slightly eastward. Model trends have
been for more heavy rain on the southern and eastern sides, so
expanded the Slight Risks in this direction on both days. Continue
to keep the risk areas broad given lingering uncertainties in
exactly where possible convective complexes track and the location
of heaviest rain. The relatively higher probabilities of flash
flooding potential may be near/over the I-35 corridor from the
Dallas-Fort Worth Metroplex south to Austin and San Antonio on
Wednesday, while it is harder to tell on Thursday. Moderate Risks
are not out of the question at some point in future cycles.
Moderate to heavy rain may continue to linger in the south-central
U.S. late week into next weekend, possibly exacerbating flooding
issues.

A shortwave interacting with a frontal boundary across the
northern tier will bring showers and storms across parts of the
northern Rockies into the Upper Midwest. Moisture anomalies should
be above the 90th percentile in Montana on Wednesday and spreading
east Thursday, while convection rides along the cusp of the
instability gradient. This supports Marginal Risks on the Wednesday
and Thursday ERO with only minor changes to the previous issuance.
By late week, combining upper level and frontal features will
allow for rainfall spreading into the east-central and eastern
U.S., with a general focus around the middle Mississippi/Ohio
Valleys into the northern Mid-Atlantic, but with ample spread in
the details at this point.

A heat wave early this week over the West should moderate by the
start of the medium range period, though above normal temperatures
may continue across interior parts of the West through the period.
Daytime highs generally could be 10 to 15 degrees above normal.
Otherwise, the rest of the country looks near normal or within a
few degrees of normal depending on quick systems moving through.


Tate/Santorelli


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