Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
820 PM EDT Wed Jul 1 2026
Day 1
Valid 01Z Thu Jul 02 2026 - 12Z Thu Jul 02 2026

..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER THE UPPER
MIDWEST AND SOUTHWEST TEXAS...

Upper Midwest and Upper Great Lakes Regions...

01Z Update: Based on the latest observational and CAM guidance
trends (especially with the HRRRs and 18Z HREF/REFS QPF exceedance
probabilities), have removed the Marginal Risk areas from the LA
Gulf Coast region and SE FL, while trimming some of the Marginal
(western flank) from the southern High Plains into the Upper MS
Valley.

Hurley

16Z Update: The SLGT risk forecast remains consistent with little
change from the previous update as the synoptic pattern evolution
maintained general continuity with the latest 12z deterministic.
HREF mean QPF from northern IA up through southeastern MN into WI
still points to an areal average of 2-3" with local spots of 4-5"
plausible through the course of the period. Radar already has
trended towards the favorable heavy precip axis aligned from
southwest to northeast from eastern NE up through north-central WI
with a flash flood warning already in place between along the
southeast MN/WI border. 12z surface analysis reflected a quasi-
stationary front situated from NE through northern IA into
southeast MN, extending north through WI. A few surface impulses
are migrating northeast along the front, aided by a quick-moving
shortwave traversing the region allowing for ample low to mid-level
ascent within the deep moisture pool and modest instability
presence over the Midwest. This current shortwave will eject
northeast into the northern Great Lakes, but a trailing mid-level
vorticity maxima will enter the area by this evening allowing for a
secondary pulse of convection across the same areas impacted this
morning. HREF probs for >3" remain elevated for the area located
between central IA, northeast into north-central WI, a correlation
for where heavy precip will overlap with both disturbances within
the confines of the persistent front in the region. Expectation is
for a large area of 2-3" with local spots between 4-6" likely over
the course of the D1. In this case, there was little reason to
deviate from the previous forecast, so the SLGT risk was generally
maintained with only minor adjustments on the northern and southern
flank of the risk.

Southwest Texas...

16Z Update: A weak mid-level impulse will continue to move from
south to north through the western flank of a broadening mid-level
ridge positioned over the eastern CONUS with the primary impact of
scattered slow-moving convection likely to impact portions of
southwest TX this morning into the early afternoon before
dissipating. A second round of convection will materialize later
this evening over the terrain as the combination of diurnal
destabilization and weak kinematic forcing will aid in
initialization of thunderstorms from the eastern NM plains down
through southwest TX. Redevelopment of a modest LLJ between
25-35kts will also play a factor in maintaining sufficient shear
and propping up any mature mesocyclones that materialize within the
buoyant environment present. PWAT anomalies remains upwards of +2
standard deviations according to the latest ECENS and NAEFS
ensembles, a signal prevalent for locally enhanced rainfall rates
across the region, allowing for a better risk of flash flooding.
Considering the nature of the current convection providing
opportunity for multiple flash flood warning issuances and another
round anticipated this evening, a SLGT risk was added across much
of southwest TX in coordination with the local Midland/Odessa WFO.

Northeast US...

16Z Update: Some variability in the signal for scattered
thunderstorms and isolated flash flood concerns offers a low-end
threat for the potential when assessing the latest 12z CAMs. The
HRRR continues to be the least bullish on the prospect with hardly
any coverage at all within the span of Upstate NY into northern New
England while a few of the CAMs continue to indicate more prolific
convective pulses that would provide locally heavy rainfall and
flash flood opportunities. HREF neighborhood probabilities for >2"
of rainfall remain modest with scattered signals of 20-40% located
across the above area(s). This threat is on the lower end of the
MRGL risk threshold, but the prospect remains when looking into the
means. As a result, maintained continuity with no adjustments
necessary from the previous forecast.

Southeast Florida...

16Z Update: Afternoon convection will fire along a sea breeze
penetrating inland across South FL with the steering pattern likely
to take cells from east to west during any convective evolution.
The greatest likelihood of flash flooding continues to point to the
urban center between Miami to Ft. Lauderdale and perhaps as far
inland as Homestead and Florida City before heavy precip shifts
into the Everglades. HREF probs for locally as much as 5" of rain
continue to be modest (20-30%) with the best chance over Miami
proper down through FL997 to the west of the metro. No changes were
necessary from the previous MRGL risk forecast.

Louisiana...

16Z Update: General forecast remains on track from the previous
update as we have begun to see the northern fringes of the inverted
trough analyzed off the Central Gulf coast move inland over
southern LA this morning. 12z CAMs continued to pin the heaviest
precip across I-10 and points south through the period with the
main threat likely relegated to the urban centers located between
Lake Charles to Lafayette and surrounding suburbs. Little change in
the prob fields indicate consistency in the signal with just some
minor fluctuations in where models have the heavier precip cores
anticipated. The MRGL risk inherited was maintained with only some
minor adjustments based on the 12z HREF blended mean QPF output
depicting a touch higher amounts further north along I-49 and
north of US190.

...Previous Discussion..

Inverted trough will maneuver around the southern periphery of a
strengthening ridge positioned to the north leading to an
increasing convergence pattern across the southern half of
Louisiana today and tonight. The blended QPF from both the HREF and
RRFS output both push closer to 2- to 3-inches across the coastal
portions of southwest/south central Louisiana. Probabilities for
>3" locally are up to 40-70% within that zone along the interstate
with some lower end probs for even >5" showing up between Lake
Charles and Lafayette proper in the latest update. One positive in
this setup is the area FFG's for all 1/3/6hr thresholds are very
high given the drier antecedent soils remaining over the area. This
should curb a more enhanced flash flood scenario, but still offer
a modest prospect given the heavy totals in the deterministic
outputs.

Kleebauer


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt