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QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
434 PM EDT Sun Jul 7 2024

Day 1 - Valid 16Z Sun Jul 07 2024 - 12Z Mon Jul 08 2024

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
COASTAL TEXAS...

16Z Update...

...Coastal Texas into Louisiana...

Beryl still has a landfall forecast prior to 12Z Monday on the
middle TX Coast (please see the NHC website for the latest
information). The most outer band is roughly along the entirety of
the TX Coast here at 16Z (only spotty heavy rain with this though) with
the inner core picked up on regional NEXRAD heading toward the
middle TX Coast. Updated timing from recent HRRRs allows some
updates to the Day 1 coverages. The inner core rainfall should
exceed 7" over much of the middle TX Coast by 12Z, warranting the
Moderate Risk from Rockport to Freeport an points north. However,
there is increased confidence on inflow bands to the right of the
track spreading up as far east as Galveston Bay and up through the
Houston metro starting around 08Z. In coordination with WFO HGX,
the Moderate Risk has been expanded through the immediate Houston
metro and now extends from San Antonio Bay to Galveston Bay.

The Marginal Risk still does not extend down all of Padre Island
with the 12Z CAM consensus for heaviest rainfall to be east from
Oso Bay where the Slight Risk begins. On the east side, far outer
bands will cross southwest LA, warranting maintenance of the
Marginal Risk there as well as the Slight Risk from Galveston Bay
to the Sabine River/TX-LA border.

...Southern Plains to the central High Plains and to the Upper Midwest...

Organized convection/MCS is over central OK and tracking southeast
which is more progressive/farther southeast than most any HREF CAM
guidance had depicted. This should focus the heaviest
redevelopment later today to be farther south over southwest OK
into Northwest TX this afternoon/evening and less so over KS. The
best guidance so far seems to be the 12Z NAMnest if it is
considered 3-4 hours too slow this morning. This served as a guide
to remove the Slight Risk for most of KS and maintain the Slight
Risk for much of OK into Northwest TX where southerly low level
flow looks to maintain 1.75" PW.

Farther north, greater synoptic forcing is present with the upper
trough extending from an upper low over northern MN to the
southwest over the central Dakotas and extending to the central
High Plains. Redevelopment of activity over the central High Plains
this afternoon/evening looks to track south over eastern CO where
the Marginal Risk was expanded. Downstream is a broken swath of
expected heavy rainfall in the moist southwesterly flow ahead of
the trough axis over eastern KS, northern MO, much of IA and into
southwest WI and western IL where the Marginal Risk was expanded a
bit. Even farther north, ahead of the upper low, redevelopment
around western Lake Superior raises an isolated flash flood threat
for the Arrowhead of MN, around through Duluth to northern WI and
far western U.P. of MI where a Marginal Risk was introduced.

...Southeast...

A stalled frontal boundary across the region will be the focus for
convection which will maintain an isolated threat for flash
flooding concerns. PWs will remain above the climatological 90th
percentile, and layered IVT suggest we may see some mid/upper level
moisture connection to Beryl. The intrusion of tropical moisture
may help bolster rainfall efficiency in what will already be a
favorable environment for heavy rainfall rates. A Marginal Risk remains
in effect for a majority of the Southeast region for this period
with a minor expansion over western NC terrain up to the VA border
per recent HRRR runs.

Jackson

Day 2 - Valid 12Z Mon Jul 08 2024 - 12Z Tue Jul 09 2024

...THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL FOR MOST OF 
EASTERN TEXAS...

21Z Update...

...East Texas through Arkansas...

12Z HREF consensus along with the 18Z HRRR feature feature a
considerable swath of heavy rain ahead and east of the Beryl track
which starts from just inland from the Middle TX coast at 12Z Mon.
An areal average of 3-8" is featured from the upper TX Coast (from
inflow bands right of the track) and in the inner core rainfall
north from Houston-Bryan TX then into southwest AR and far
southeast OK. The Moderate Risk is expanded a bit more northeast
through the rest of TX as well as farther east toward the LA border for
the inflow bands right of the track. At least locally considerable
impacts can be expected. Fortunately this is a fairly progressive
system per NHC forecast forward speed of at least 10kt. Given
increased confidence in the heavy rain swath extending through
western/central AR and far eastern OK warrants expansion of the 
Slight Risk up to the MO/AR border. A trend in the track to the
right continues and will need to be monitored in future outlooks,
especially considering how much inflow into the Ozark
terrain/topographical enhancement will occur.

Elsewhere, tropical moisture from Beryl into a cold frontal 
boundary draped over the southern Plains should focus scattered 
heavy rainfall over much of OK into the TX Panhandle where a 
Marginal Risk is maintained/expanded into northwest TX. 

...Southeast...

Convection in proximity to the lingering frontal boundary within PW
anomalies of 2 to 3 sigma will persist over the southern
Appalachians, much of GA, southern SC and northeast FL where a
Marginal Risk is maintained. Recent rains have increased soil 
saturation levels, so this additional activity allows a threat for
isolated flash flooding.

Jackson

Day 3 - Valid 12Z Tue Jul 09 2024 - 12Z Wed Jul 10 2024

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS THE MIDDLE
MISSISSIPPI VALLEY...

...Mid-South through Midwest...

Beryl is expected to quickly phase with an upper trough as it lifts
northeast from Arkansas Tuesday. A swath of heavy rainfall is
expected to persist through this extratropical transition with the
12Z GFS/ECMWF in good agreement with another shift to the right
with the track which is in line with NHC forecasts. 3-6 inches over
southeast MO, south-central IL to central IN (along with an 
additional 1.5" or so over northern AR) warrants a Slight Risk that
includes the St. Louis metro. Increased confidence in central Gulf
coast precip, but limited inflow banding between the coast and the
remnants over the Mid-South warrants trimming the Marginal Risk on
the south side, while the more progressive and right trend in the
track warrants bringing the Marginal Risk into western OH. 

...Southwest...

Monsoonal moisture feeds over eastern AZ through the southern
Rockies warranting maintenance of the Marginal Risk for most of 
New Mexico, southeast Arizona into southern Colorado with
particularly considerations for burn scars and areas that have 
seen ample rainfall recently.

...Southeast...

Maintained the Marginal Risk over southern Georgia through the
northern FL Peninsula given the abundant moisture over the region
and diurnal forcing for locally heavy rainfall, especially for 
northeast Florida. General consensus of 12Z guidance continues to
suggest 1 to 2 inches with local maximums of 3 to 4+ inches.

...Northeast...

Some moisture from the Southeast and ahead of Beryl interacts with
a front over the Northeast. Guidance is rather light with activity
mainly in New England, so for now the Marginal Risk was trimmed 
back to north of NYC.

Jackson
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