Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
307 PM EDT Sat Jun 27 2026
Day 2
Valid 12Z Sun Jun 28 2026 - 12Z Mon Jun 29 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS EASTERN
NORTH CAROLINA INTO FAR SOUTHEAST VIRGINIA...

19z Update: A Slight risk was introduced across eastern NC into far
southeast VA. The MCV currently over southern IL will be moving
across NC tomorrow. By afternoon a convective focus ahead of this
feature should occur across the aforementioned Slight risk area.
Guidance indicates a mainly progressive convective mode, however
coverage should be enough to result in some cell mergers and brief
training enhancing rainfall rates/duration. Both the 12z HREF and
REFS indicate a 15-40% chance of FFG exceedance, and rainfall
today/tonight could lower FFG a tad more before then. Thus an
isolated to scattered flash flood threat appears probable tomorrow
afternoon across this region.

The Marginal risk was made broader over the Mid-Atalntic as well.
Isolated to scattered convection over WV into VA likely won't be
as organized as the activity over NC, but could be slower moving
and within a favorable environment for heavy rainfall rates. Over
eastern TN into northern GA a training convective axis could be
ongoing at 12z Sunday, although should be weakening.

A Marginal risk was also added over west TX, where dryline
convection should pose a localized flash flood risk.

Chenard

...Previous Discussion...

...Montana...
Upper low center pivots over Montana Sunday with the surface low
stalling along the international border . This maintains comma
head/deformation zone rain shifting into northwest MT where terrain
enhances rates at lower elevations and snow generally at or above
6500 feet. This is more of an areal flood concern given a lack of
instability, but localized rates may warrant some rapid flooding
concerns where precip bands are most stagnant. 00Z consensus
rainfall remained in the 1 to 3 inch range around Glacier National
Park onto the adjacent high plains in northwest MT. A marginal risk
was maintained for this area.

...Upper Midwest...
The warm sector of this anomalous low over MT will shift eastward
allowing an airmass with robust Gulf moisture advection up the
length of the Great Plains through the Upper Midwest. The
development of surface low pressure over South Dakota will aid the
moisture transport at the low levels and provide a lifting
mechanism. Focusing on this...there was an eastward expansion and a
bit of a southward expansion of the previously issued Marginal
risk area.

...Coastal Carolinas/Mid-Atlantic...
Added a small, targeted Marginal along the eastern seaboard where
precipitation lingers from the Day 1 period. Blending disparate QPF
in such cases tends to yield low amounts...but the area had the
best overlap with highest precipitable water values and an area
where ensemble members with differing cores tended to cluster. With
such high moisture...localized downpours and heavy to excessive
rainfall is a concern from any storm that can develop regardless of
the meager focusing mechanism.

Bann/Jackson


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt