FOUS30 KWBC 190921
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
521 AM EDT Sun Jul 19 2026

Day 1  Valid 12Z Sun Jul 19 2026 - 12Z Mon Jul 20 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHWESTERN U.S. FROM WEST TEXAS TO SOUTHERN UTAH, AS WELL AS
EASTERN NORTH CAROLINA AND THE VIRGINIA TIDEWATER REGION...

...Southwestern U.S....
Overall, the synoptic pattern remains much the same, with the
monsoon ridge remaining favorably aligned. PW anomalies of 2-3 std
dev above normal will remain across much of the highlighted area.
This moisture, along with sufficient instability, and areas of
enhanced ascent afforded by easterly-drifting mid-level energy.
will support another day of widespread convective activity. Slow-
storm motions along with likely cell-mergers will raise the threat
for locally heavy amounts and flash flooding concerns. Flash
flooding remains a distinct threat in slot canyons, dry washes,
burn scars, and low desert areas via mountain outflows. The Slight
Risk highlights the area where HREF and REFS guidance indicate the
threat for 1-2 inch amounts is greatest. The REFS, and to a lesser
extend the HREF, indicate that heavier totals of 3+ inches are
possible over portions of West Texas along the Mogollon Rim down
into southeastern Arizona.

...Lower Missouri Valley to Southeastern Virginia and Eastern North Carolina...
A targeted Slight Risk remains centered over eastern North
Carolina and extends into southeastern Virginia. Convection will
develop ahead of a slow-moving cold front that will be dropping
into a very moist (PWs 2+ inches) and unstable (MUCAPE > 2000
J/kg) environment, while some modest right-entrance region upper
jet forcing will offer some enhanced ascent. Heavy totals appear
likely, with both the HREF and REFS showing high neighborhood
probabilities for amounts over 3 inches within the Slight Risk area.

Less organized activity is expected back along the front extending
across the southern Appalachians, Tennessee Valley, and parts of
the lower Ohio, mid Mississippi, and lower Missouri valleys. While
widespread heavy totals are not expected, the moisture-rich
environment (PWs 1.75-2 inches) is expected to support storms
capable of producing localized heavy amounts and isolated runoff concerns.

...Eastern Dakotas into the upper Mississippi Valley...
A shortwave moving off of the top of the western U.S. ridge will
interact with a frontal system advancing through the northern
Plains into the Upper Midwest. An amplifying west-southwesterly
low level jet will support increasing PWs (1.75-2 inches) and
instability east of a warm front. The overnight guidance differed
greatly on the details but continued to present some signal for
backbuilding and training storms, capable of producing locally
heavy rates within the area highlighted by the Marginal Risk.

...Eastern Gulf Coast into the Southeast...
An area of low pressure located over the northeastern Gulf is
gradually becoming better defined, with additional development
becoming more likely. The footprint for heavy amounts through early
Monday is expected to remain mostly offshore, although some
heavier amounts along the immediate Florida Gulf Coast cannot be
ruled out. Therefore, the Marginal Risk was maintained.

An axis of enhanced low level convergence and pooling moisture to
the north is still expected be a focus for diurnal storms capable
of producing heavy rates. Therefore, a Marginal Risk was maintained
from the central Gulf Coast northward into the Tennessee Valley.
HREF and REFS indicate localized totals exceeding 2 inches are
likely along this corridor.

Pereira
 

Day 2  Valid 12Z Mon Jul 20 2026 - 12Z Tue Jul 21 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
WEST TEXAS, NEW MEXICO, AND ARIZONA...

...Southwest and Great Basin...
Mid-level energy moving west of the region, and dry air advection
from the south will begin to diminish the heavy rainfall and flash
flooding threat over West Texas. However farther west, the
monsoonal moisture plume will remain firmly in place, ensuring
another day of high-efficient rainfall production over portions of
the Southwest and Great Basin.

Models show the upper high originally centered over Utah and
Colorado beginning to slide southeast, allowing moisture and
energy to spread northwest into the Great Basin and along the
western slopes of the Sierra Nevada -- raising the potential for
increasing storm activity and isolated runoff concerns in those area.

The greater heavy rainfall and flash flooding threat will remain
focused from southwestern New Mexico and southeastern Arizona
northwestward along the Mogollon Rim into northwestern Arizona.
This is expected to be the focus for better synoptic forcing and
greater instability -- supporting intense short-duration rain rates
that will elevate the risk for flash flooding, especially in areas
of complex terrain, dry washes, and burn scars.

...Upper Great Lakes...
An amplifying upper trough supported by energy diving out of
Canada will advance from the upper Mississippi Valley to the upper
Great Lakes. Strong southwesterly to west-southwesterly low level
inflow will continue to sustain deep moisture ahead of the cold
front and across the advancing warm front. This moisture along with
strong forcing, produced in part by left-exit region upper jet
dynamics, will generate organized convection capable of producing
rainfall rates of 1-2 in/hr. Fast storm motions should limit the
overall heavy accumulation and flash flooding threat. However,
localized short-term training could raise at least some isolated concerns.

...North Carolina and Southern Virginia...
Maintained a Marginal Risk across this area. Apart from the GFS and
REFS, the general model consensus indicates that activity will be
less organized. However, a lingering boundary and corresponding
pool of deep moisture (PWs 2+ inches) will support additional
storms capable of producing heavy downpours. Should the guidance
begin to trend more toward the GFS and REFS, a targeted upgrade
may required, especially if more models begin to show back-to-back
days of overlapping heavy amounts.

...Gulf Coast...
The models continue to show the footprint of the heaviest amounts
associated with the disturbance over the northern Gulf remaining
mostly offshore. Therefore maintained only a Marginal Risk along
the coast from West Florida to southeastern Louisiana. Moisture
pooling along an axis of enhanced low level convergence northwest
of the circulation may extend the threat for heavy rainfall further
inland into the far lower Mississippi Valley.

Pereira
$$
--- MultiMail/DOS
 * Origin: capitolcityonline.net * KY, USA (618:250/10)