Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
839 PM EDT Sun Jul 26 2026
Day 2
Valid 12Z Mon Jul 27 2026 - 12Z Tue Jul 28 2026

...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL ACROSS THE FOUR
CORNERS STATES ONTO THE CENTRAL PLAINS AND GREAT LAKES/OHIO VALLEY
INTO THE NORTHEAST...

...Four Corners States onto the Central Plains...
Center of upper high shifts south from CO to NM through tonight
which will direct more ridge topping diurnally-driven activity from
the central Rockies onto the central Plains on Monday compared to
today. Meanwhile continued monsoonal activity is expected across
the Four Corners states again. Favored focus areas for QPF are
again along the Mogollon Rim in AZ and in CO, though this time it's
east from the Continental Divide instead of west like today. Only
a minor expansion to the Marginal Risk is noted with the HREF
favoring central Plains activity into southwestern South Dakota.


...Great Lakes and Ohio Valley into the Northeast US...
A shortwave trough shifts southeast over northern Minnesota Monday
morning and through the Upper Great Lakes Monday
afternoon/evening. This is in northwest flow downstream of the
upper level ridge axis stalled over the western Dakota border.
Increasingly difluent flow ahead of the shortwave will lead to the
consolidation/ strengthening of a low pressure system Monday night
which increases forcing for heavier rainfall over the Great
Lakes/Ohio Valley. The Marginal Risk was expanded west along the
WI/UP of MI border for morning activity, down through eastern IL
for downstream effects from tonight, and farther downstream into
New Jersey for Monday night activity beginning before it becomes
more significant on Tuesday.


...Tampa Bay...
Troughing currently on the east side of the FL Peninsula shifts to
the Gulf side tomorrow. Excellent agreement among 12Z HREF/REFS
guidance for repeating heavy thunderstorms across greater Tampa Bay
Monday morning into the afternoon. Consensus average QPF is 2-4"
with potential for 6" from both the HREF and RRFS. A Marginal Risk
for flash flooding is warranted in this scenario, especially for
urbanized drainage concerns.

Jackson


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