Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
836 PM EDT Sun Jun 28 2026
Day 3
Valid 12Z Tue Jun 30 2026 - 12Z Wed Jul 01 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE GREAT LAKES...NORTHERN NEW ENGLAND AND OVER SOUTHWEST TEXAS...

...Northern New York State into Northern New England...
Shortwave energy riding up over the top of an Ohio Valley upper
high across southeast Canada will make its way into portions of
northern New England on Tuesday and help strengthen the low level
westerly flow into a frontal boundary. Models still point to the
potential for organized convection late Tuesday or in the early
morning hours of Wednesday. There remained a strong enough model
signal for organized convection moving northwest to southeast
resulting in heavy rains and isolated runoff issues, enough for a
Marginal Risk, but not cohesive enough amongst the guidance for a
stronger risk level.

...Southern High Plains...
Precipitable water values of 1 to 1.5+ standard deviations above
climatology for this time of year remain over the Southern High
Plains. Embedded shortwaves in this southwest mid to upper level
flow will support increasingly scattered convection in this
anomalously moist airmass, with locally heavy rains and isolated
runoff issues possible causing problems in burn scars and dry
washes/arroyos.

...Upper MS Valley/Upper Lakes...

21Z update... Modest southward adjustments were made to the western
bounds further into northern Nebraska and for the northern
boundary in central Minnesota. This maintains a southwest to
northeast orientated axis from the Plains to Michigan.

Campbell

Convection expected to continue along and ahead of a surface front
moving slowly across the Upper MS Valley. Favorable right entrance
region jet dynamics ahead of this front in an axis of above
average precipitable water values will support potential for heavy
rains with organized convection along and ahead of this cold front
with isolated runoff issues possible. This outlook largely
maintained the adjustments made previously...although additional
southerly shifts cannot be ruled out given the flow pattern
expected.

...Central Gulf Coast...

21Z update... The environment described below is still expected
although the guidance shifted the QPF footprint a bit east than
previous cycles. As such, the Marginal Risk area was adjusted to
cover more of the Florida Panhandle and reduce coverage over
eastern Louisiana and souther Mississippi.

Campbell

Some of the guidance has a signal for heavy rainfall across the
area, caused by an easterly wave coming off the tail end of a
frontal boundary. Considering the moisture and instability
expected, at least urban areas could receive flash flooding so
maintained a Marginal Risk for this possibility.

Bann

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt