FOUS30 KWBC 230829
QPFERD
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Fri Aug 23 2024
Day 1
Valid 12Z Fri Aug 23 2024 - 12Z Sat Aug 24 2024
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE FOUR
CORNERS REGION/INTERMOUNTAIN WEST AND PARTS OF THE SOUTHEAST US...
...Southeast US...
Maintained the Marginal risk area that was introduced on Thursday
over portions of northeast Florida...and expanded the area
northeastward along the Georgia coast line. 00Z runs of the HREF
increased the neighborhood probabilities of 1 to 2 inch per hour
rates in response to a frontal boundary..and associated
convection...being a bit closer to the coast than shown by earlier
runs.
...Southwest US...
Moisture feeding northward into the Southwest US will begin to be
channeled into a more narrow corridor disrupted today...leading to
a somewhat smaller coverage of late day and evening convection
capable of producing heavy rainfall. A secondary focus across the
terrain in Southeast AZ over into the NM Bootheel will also be an
area that could see some scattered heavy rain signals with some
support from global deterministic and ensemble members. Current QPF
signal is modest with areal averages and the setup is more benign
in the grand scheme, especially considering the previous active
periods.
Bann
Day 2
Valid 12Z Sat Aug 24 2024 - 12Z Sun Aug 25 2024
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST/FOUR CORNERS AND SOUTH FLORIDA...
...Southwest and Four Corners...
Lingering moisture and relative instability coupled with
progressive shortwaves cutting through the Interior Mountain West
will set up another round of isolated convection during the
afternoon and early evening hours on Saturday before a gradual
dissipation with the loss of diurnal heating. Pockets of heavy
rainfall are still forecast across a similar corridor as on Day 1,
so there is some concern that the antecedent conditions could be
favorable for greater impacts pending what occurs leading up to the
start of the forecast period on Saturday morning. Overall ensemble
QPF footprint still indicates a max of 1-2", at best, within the
strongest cores. This is still enough for flash flooding within
complex terrain and especially around any burn scars. The previous
MRGL risk was relatively unchanged.
...South Florida..
Incoming moisture flux with roots from the Caribbean will make
headway into South Florida on Saturday with area precipitable water
anomalies approaching 2 deviations above normal. The increasing
moisture will be in proximity to a quasi-stationary front to the
north...with a sharp delineation point of where the moisture
pooling will reside. A Marginal risk area was maintained across
the Southern FL Peninsula.
Bann
Day 3
Valid 12Z Sun Aug 25 2024 - 12Z Mon Aug 26 2024
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST/FOUR CORNERS AND SOUTH FLORIDA...
As an upper high over the Southern Plains begins to move eastward
and away from the Southwest...another push of moisture and
shortwave energy will move northward. This will sett up another
round of isolated to widely scattered thunderstorms capable of
producing flash flooding or run off problems within complex
terrain and especially around any burn scars. Given the fetch of
moisture from the southeast...the areal coverage was expanded
somewhat compared with the size of the Marginal risk area on Dy 2.
Bann
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