Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
350 PM EDT Sat May 9 2026
Day 1
Valid 16Z Sat May 09 2026 - 12Z Sun May 10 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
SOUTHERN LOUISIANA AND SOUTHERN MISSISSIPPI...
A complex of storms continues this morning along and south of a
quasi-stationary frontal boundary through the FLorida Panhandle,
coastal Alabama and Mississippi, and southwest into southeastern
Louisiana. While current radar observations and hi-res guidance
trends show that much of this line has and will continue to move
offshore into the Gulf, guidance suggests forward
propagation/potential additional development is likely eastward
along the boundary through the Florida Panhandle and north Florida.
Hi-res guidance shows rain rates as high as 2"+ per hour and MRMS
observations over the last few hours support this with the
available deep Gulf moisture south of the boundary. An easterly
component to storm movement along the east-west oriented boundary
may lead to some more prolonged periods of heavy downpours as well.
However, the overall progressive nature of the system as well as
locally high FFGs should keep impacts isolated.
Meanwhile, the latest 12Z hi-res guidance shows another round of
storms developing into the afternoon hours with daytime heating
east of a dryline through eastern Texas as an upper-level shortwave
approaches the region. Some additional storms are also possible
along the outflow/effective boundary west into southwestern
Louisiana, and a cluster of storms that has maintained strength
over the northwestern Gulf may eventually reach the area as well.
Given the noted sources of heavy rainfall potential and moderate
HREF probabilities of greater than 3" totals/low probabilities of
greater than 5" totals, the Slight Risk was extended west into
southwestern Louisiana. The flash flood risk later today is less
clear further east across southeastern Louisiana and especially
into southern Mississippi as the effective front slides south with
this morning's storms. However, given lingering rainfall for much
of the area, uncertainty with the incoming cluster of storms over
the northwestern Gulf, and at least the HRRR suggesting the
potential the additional development further west this afternoon
may maintain/progress eastward later this evening/overnight, have
left the Slight Risk as is for now.
Putnam
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
350 PM EDT Sat May 9 2026
Day 2
Valid 12Z Sun May 10 2026 - 12Z Mon May 11 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN PLAINS AND THE ARKLATEX...
...2030Z Update...
Prior synoptic overview of the forecast remains on track. The
inherited Marginal was adjusted based on the now-avaible hi-res
guidance with a general southwesterly shift to focus on expected
convection ahead of the cold front and east of a dryline. Storms
may be ongoing at the start of the period further north over
Oklahoma and could maintain into Arkansas and even northern
Louisiana. Given uncertainty on the extent and duration of these
storms and early morning lull in instability, there is no extension
of the outlook based on their potential. However, they may
ultimately impact the northern extent of new development across
Texas later tomorrow afternoon and evening. There could also be the
need for a targeted Slight Risk where convective coverage looks to
maximize immediately ahead of the cold front with initial cell
clustering/merging and upscale growth, currently progged along and
south of the I-20 corridor across north-central into central Texas.
Some of the hi-res guidance suggests locally heavy totals of 3-4"
could be possible. However, given the overall progressive nature of
the front, high FFGs, and uncertainty with respect to where this
corridor may ultimately set up (with potential overnight/early day
convection influence), a Marginal Risk remains sufficient for now.
Putnam
...Previous Discussion...
The forecast reasoning and outlook area remains largely consistent,
with a Marginal Risk area extending from north/central Texas into
the ArkLaTex. A cold front dropping south through the Plains will
become a primary focus for deepening moisture (PWs increasing to
around 1.5 inches) and storm development.
Synoptic support will strengthen as shortwave energy moves into the
base of a broader-scale trough, placing the region within an area
of strong ascent, supported by coupled upper-jet forcing. This
combination of moisture and favorable dynamics, along with
increasing instability, will promote broadening storm coverage by
the afternoon. While storms will eventually gain a more steady
southward progression, initial storm organization may be
characterized by slow movement and mergers. These factors combined
with the potential for high rainfall rates, support the
maintenance of the Marginal Risk for localized flash flooding.
Pereira
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
350 PM EDT Sat May 9 2026
Day 3
Valid 12Z Mon May 11 2026 - 12Z Tue May 12 2026
The probability of rainfall exceeding flash flood guidance is less
than five percent.
Putnam
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
202 PM EDT Sat May 9 2026
An eastern Canadian closed upper-level low will continue to help
support a mean longwave trough down into the eastern U.S. This
pattern will support a persistent cyclonic circulation aloft,
allowing multiple shortwave energies to approach the base of the
mean trough from upstream. Impulses will lead to the progression of
wavy frontal systems, bringing periods of showers and
thunderstorms through the eastern half of the country next week. By
mid to late week, each system eventually works downstream to the
Atlantic to spawn moderate coastal cyclogenesis with wrapping
moisture feeds before lifting up/off the East Coast.
Upstream, an eastern Pacific closed low will advance inland
sometime mid to late next week, focusing organized light to
moderate precipitation across portions of the northern Great Basin,
Pacific Northwest, and northern Rockies. A developing downstream
surface low and frontal boundary will form over the Northern Tier,
bringing chances for showers and thunderstorms across the northern
Plains into the Upper Midwest, and then the Great Lakes/East. Deep
boundary layer mixing may bring some gusty winds across the Rockies
and Plains with system passage.
Temperatures across the eastern half of the U.S. will remain near
to below normal through most of next week. Meanwhile, a ridging
pattern will keep well above normal temperatures in place across
much of the western U.S., with pre-frontal warmth spreading
eastward into the central U.S. mid to late week. Several high
temperature records are likely to be tied or broken through the
period.
Schichtel/Miller
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
202 PM EDT Sat May 9 2026
An eastern Canadian closed upper-level low will continue to help
support a mean longwave trough down into the eastern U.S. This
pattern will support a persistent cyclonic circulation aloft,
allowing multiple shortwave energies to approach the base of the
mean trough from upstream. Impulses will lead to the progression of
wavy frontal systems, bringing periods of showers and
thunderstorms through the eastern half of the country next week. By
mid to late week, each system eventually works downstream to the
Atlantic to spawn moderate coastal cyclogenesis with wrapping
moisture feeds before lifting up/off the East Coast.
Upstream, an eastern Pacific closed low will advance inland
sometime mid to late next week, focusing organized light to
moderate precipitation across portions of the northern Great Basin,
Pacific Northwest, and northern Rockies. A developing downstream
surface low and frontal boundary will form over the Northern Tier,
bringing chances for showers and thunderstorms across the northern
Plains into the Upper Midwest, and then the Great Lakes/East. Deep
boundary layer mixing may bring some gusty winds across the Rockies
and Plains with system passage.
Temperatures across the eastern half of the U.S. will remain near
to below normal through most of next week. Meanwhile, a ridging
pattern will keep well above normal temperatures in place across
much of the western U.S., with pre-frontal warmth spreading
eastward into the central U.S. mid to late week. Several high
temperature records are likely to be tied or broken through the
period.
Schichtel/Miller
