373
FXUS02 KWBC 151904
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
304 PM EDT Tue Jul 15 2025

Valid 12Z Fri Jul 18 2025 - 12Z Tue Jul 22 2025

...Central Gulf Coast heavy rain threat into next weekend...


...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 an area of low
pressure currently moving inland across northern Florida to
potentially develop into a tropical cyclone once it emerges over
the northern Gulf in the next day or so. Regardless of development,
heavy rainfall and flash flooding threats are increasingly likely
for parts of the central Gulf Coast later this week and into the
weekend. Meanwhile, monsoonal moisture will be in place through the
period in the Four Corners states to the south- central High
Plains. Upper ridging from the southern Plains to the Southeast
will promote summer heat into early next week.


...Guidance/Predictability Assessment...

Model guidance continues to advertise an overall progressive
synoptic pattern dominated by a strengthening subtropical ridge
across the southern U.S. and a fairly fast moving jet and wave
train across the north. Model agreement remains reasonable for most
of the medium range period, aside from the typical small scale
differences in timing and amplitude of individual shortwaves.
Similar to last night`s package, the WPC forecast consisted of a
blend of 00Z and 06Z deterministic guidance before introducing
increasing weighting of ensemble means later in the period.

The National Hurricane Center continues to show a moderate chance
of tropical development of an area of low pressure that is now
beginning to move inland across northern Florida and is forecast to
drift westward into the northern Gulf over the next day or so. The
latest guidance suggests a generally weak surface reflection
meandering along or just south of the Gulf Coast before turning
northward and moving inland over Louisiana around a weakness in the
subtropical ridge on Day 4/Thursday. The area of low pressure is
expected to quickly dissipate by Day 5 or 6, though remnant
moisture will likely still have an impact on QPF placement and
magnitude downstream.


...Weather/Hazards Highlights...

An area of low pressure is forecast to move west across northern
Florida and emerge in the northern Gulf over the next day or so.
Regardless of any kind of tropical development, moisture above the
90th percentile looks will impact the central Gulf Coast by the
medium range leading to heavy to excessive rainfall. There remains
enough consistency in the model timing of the heavy QPF and the
abundance of tropical moisture to maintain a moderate risk on the
Day 4/Friday Excessive Rainfall Outlook (ERO) across southern
Louisiana. However, the latest guidance has definitely shifted a
bit farther north and west compared to last night, so followed suit
with the moderate risk area as a result. A broader slight and
marginal risk is maintained from far east Texas into parts of
Mississippi, Alabama, and the Florida Panhandle. Moisture in this
area may be slower to move given the larger scale ridge in place,
and so a slight risk seemed warranted for the Day 5/Saturday ERO as
well across Louisiana. Similar to Day 4, shifted the slight risk a
bit farther north and west compared to continuity given the latest
QPF signal. Moderate rainfall may extend into Sunday as well but
with much more uncertainty.

Much of the nation from the Rockies eastward will be active with
typical summertime convection in a warm and unstable airmass during
the period. A cold front shifting into the Ohio Valley/East on
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 was enough agreement in the guidance for
the addition of a slight risk across parts of the central
Appalachians on Friday with ample moisture in an area of relatively
low flash flood guidance. There is also 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 Saturday.
Therefore, slight risks are in place for both Friday and Saturday
on the EROs associated with this activity.

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 parts of Colorado and Utah for both Friday and
Saturday. 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
looks to remain near or below normal (on the order of 5-10 degrees)
for this time of the year through much of the period, with some
moderation at times. Elsewhere, despite temperatures being near or
only a few degrees above normal, the persistence of ridging over
the Southeast will keep a moderate to major HeatRisk in place for
the region, stretching westward with time into the
Tennessee/Mississippi Valley.


Miller/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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