958
FXUS02 KWBC 142002
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
402 PM EDT Mon Jul 14 2025

Valid 12Z Thu Jul 17 2025 - 12Z Mon Jul 21 2025

...Central Gulf Coast heavy rain threat...


...Overview...

A fairly typical summertime pattern will remain in place through
much of the medium-range period with an expansive and building
upper ridge stretched across the southern U.S. and progressive
upper troughs moving through the northern tier states. Convection
is likely ahead of a cold front across the interior eastern U.S.
and north of a warm front across the Midwest. Farther south, the
National Hurricane Center continues to monitor the potential for a
low pressure area east of Florida to develop into a tropical
cyclone and reach the central portion of the Gulf Coast during the
latter half of this week, bringing heavy rain threats initially
across parts of Florida and then into central Gulf Coast later this
week regardless of tropical development. Meanwhile, monsoonal
moisture is forecast to increase through the period in the Four
Corners states to the south-central High Plains. Upper ridging from
the southern Plains to the East will promote summer heat through
late week into next weekend.


...Guidance/Predictability Assessment...

Model guidance has persistently shown agreement for a low
amplitude and progressive synoptic weather pattern across the
northern tier states through the medium-range period, but with
variability in the details and timing of the shortwaves within
the longwave troughs. These details affect the timing and
placement of surface fronts and QPF, but a general model compromise
worked well through the forecast period with larger proportion
from the ensemble means late in the period to handle these
differences. A couple of shortwaves rounding a ridge over the
northeast Pacific show more uncertainty. The model blend yielded a
faster eastward progression of the wave moving across the Northeast
but a slower progression of the wave moving across the Pacific
Northwest on day 7.

Regarding the low pressure area east of Florida that the National
Hurricane Center has been monitoring for tropical cyclone
formation, the ICON model has been the most aggressive with
development since yesterday. The CMC also has shown development
tendency with this system while the ECMWF and GFS are the least
enthusiastic with respect to tropical cyclone development regarding
that system. Regardless of tropical cyclone development, the
timing of the rain has been relatively consistent among different
models as the Bermuda High begins to build westward toward the
Southeast U.S. The WPC QPF is comparable to continuity for this
system, but still lower than the NBM at this point.


...Weather/Hazards Highlights...

A low pressure system that has developed near the tail end of a
dissipated front is forecast to move east across northern Florida
and potentially reach the central Gulf Coast late this week.
Tropical moisture above the 90th percentile looks to reach the
central Gulf Coast by the medium range, after a wet early part of
the week in Florida. Given the consistency in the model timing of
the heavy QPF and the abundance of tropical moisture, a slight risk
of excessive rainfall is maintained from portions of Louisiana,
and far southern Mississippi and Alabama for both Day 4/Thursday
and Day 5/Friday. A Marginal Risk is included on both the Day
4/Wednesday and Day 5/Thursday Excessive Rainfall Outlook (ERO) for
those areas. The CMC and Icon suggest that the heavy rain would
move farther inland next weekend if the system develops into a
tropical cyclone.

Much of the nation from the Rockies eastward will be active with
typical summertime convection in a warm and unstable airmass. A
cold front shifting into the Ohio Valley/East Thursday and Friday
will support showers and thunderstorms with ample moisture and
instability, resulting in a heavy to excessive rainfall threat.
Both the Thursday and Friday EROs show a very broad Marginal Risk
across these regions and stretching back westward into the mid-
Mississippi Valley. There is increasing model agreement for a
synoptic pattern that favors the setup of west-to-east training of
convection to the north of a lifting warm front ahead of a
developing low pressure wave on Friday into early Saturday.
Therefore, an area of Slight Risk has been introduced on Day 5 that
covers the vicinity of eastern Nebraska to southwestern Iowa and
into northwestern Missouri.

Farther south, monsoonal moisture will gradually increase in
coverage across the Southwest/Four Corners/southern Rockies region.
Marginal Risks are in place across much of Arizona and New Mexico
and stretching into Colorado for both Thursday and Friday. Areas
like burn scars and urban areas would be of greatest concern for
flash flooding. The monsoon pattern should continue into next
weekend.

Temperatures in the High Plains to the northern/central Plains
will be well below normal (on the order of 10-15 degrees) for this
time of the year into late week, but should warm closer to average
by the weekend. Modestly above normal temperatures in the East
looks to equate to some major (level 3 out of 4) HeatRisk for
Thursday into Friday, but this should moderate and shift southward
into the Southeast next weekend.


Kong/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










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