Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
428 AM EDT Sun Jun 29 2025
Day 2
Valid 12Z Mon Jun 30 2025 - 12Z Tue Jul 01 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHERN ROCKIES EASTWARD INTO THE MID ATLANTIC...

Similar to today...convection is expected to develop within a
region of decent CAPE and precipitable water values in excess of 2
standard deviations above climatology. Except for some mid-level
westerly flow around the Great Lakes to provide some shear
there...the flow farther south should be fairly meager (but offset
by steeper low-level lapse rates). This sets up the potential for
some local rainfall rates in excess of 1 inch per hour that results
in excessive rainfall from the Southern Rockies/Western High
Plains east/northeastward into the Ohio Valley and parts of the
Mid-Atlantic region on Monday and Monday night.

A weakening surface boundary will help focus some of the threat
for heavier rainfall but its placement remains quite uncertain.
One area that is still being monitored for a potential upgrade to a
Slight Risk are parts of the Upper Ohio Valley and central
Appalachians (centered over western PA). The synoptic setup with a
stationary/warm front stretching across southern PA and an
approaching cold front from the west should help foster greater
coverage in showers/storms within a moist environment, but storm
motions within a mean column wind of 30kts could limit the flooding
threat even though this area remains sensitive to intense
rainfall. Therefore, a Marginal Risk was maintained to highlight
the threat for isolated flash flooding.

Snell/Bann

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