Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1144 AM EDT Sun Jun 21 2026
Day 2
Valid 12Z Mon Jun 22 2026 - 12Z Tue Jun 23 2026

...THERE IS A SLIGHT RISK IN EFFECT FROM THE SOUTHERN PLAINS TO THE
NORTHEAST...

...Northeast and Mid-Atlantic...

The day 2 forecast period will feature a progressive trough axis
pushing from the Great Lakes to the Northeast with a trailing
frontal boundary reach southwest to the Southern Plains and above
average PWs along the axis to help create excessive rainfall
concerns. Areas of the Northeast and I-95 corridor as south as
Washington D.C. are subject to thunderstorm prospects with the
best chance for flash flooding likely to occur in the urban
footprint from D.C. to NYC with an expansion inland to central PA.
Current probs off the latest ensembles and National Blend indicate
a large zone of 30-50% probs for >2" across the aforementioned
area above with deterministic outputs closer to 2-3.5" into parts
of Southern New England. The 00z HREF (only covers through 00Z
6/23) and 00Z REFS indicate 30-60% neighborhood probabilities for
at least 2" per 6-hrs from D.C. to NYC and would be enough for
some urban flash flooding concerns. There has been additional
uncertainty farther north and east with how far to extend the SLGT
risk, but given typical mesoscale uncertainties and limited
instability, in coordination with local forecast offices the SLGT
risk was confined a bit. Look for additional refinements once the
full suite of CAMs is available, especially with increasing PWs
near the 90th climatological percentile and a nearby warm front in
the area for potential focused axis for thunderstorms.

...Southern Plains to Central Appalachians...

Across the Southern U.S., heavy precipitation will preclude
another round of convection forming along a quasi-stationary front
draped from the Southern High Plains to the Southeastern CONUS.
Probs for >1" are highest in-of the areas of Eastern OK into the
Lower Mississippi and southwestern Tennessee Valleys. Elevated
theta_E's and PWAT anomalies +2 dev. or greater indicate a
formidable environment capable of continued heavy rain potential
that will likely produce rainfall of 2-4", at least in some of the
thunderstorm activity that develops. The focal point along the
front will likely be where the heaviest rain will occur, or at
least be a low-level convergence mechanism that can enhance
regional convection. There's high enough confidence in the location
of convection for the D2 period to overlap with areas that will
have seen several inches the periods prior which led to a level 2/4
SLGT risk positioned over portions of the Southern Plains through
parts of the Southern Plains, Lower Mississippi Valley and
neighboring Tennessee Valley. The risk extends through the Smokey
Mountains up into parts of the Central Appalachians in eastern KY
up into WV as the convergence regime follows the frontal
positioning over these areas. Greatest chances for multiple rounds
of slow-moving thunderstorms capable of 2"+ hourly rainfall rates
currently appears to be over southeast OK into central AR and will
be monitored closely once CAMs are within range of the forecast
time period. Latest "longer range" REFS and HREF probabilities for
at least 3" are scattered throughout the region.

Snell


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