FOUS30 KWBC 290759
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
359 AM EDT Mon Jul 29 2024

Day 1
Valid 12Z Mon Jul 29 2024 - 12Z Tue Jul 30 2024

....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE OHIO VALLEY, UPPER TENNESSEE VALLEY INTO THE SOUTHERN APPALACHIANS...

West northwesterly mid to upper level flow will persist during the
upcoming day 1 period from the Northern Plains, east southeastward
through much of the Mississippi Valley, Ohio Valley, Southern to 
Central Appalachians, Mid-Atlantic and Southeast. Embedded 
shortwaves in this flow will support another day of active 
convection across much of these areas where PW values will be
mostly above seasonal averages. A slight risk area was drawn where
the latest HREF neighborhood probabilities were the highest for 1,
2 and 3"+ totals and overlapped the lower FFG values and observed 
precip axis from recent rains. This results in a slight risk from 
southern Illinois, east-southeast through the Ohio Valley, Upper 
Tennessee Valley into the Southern Appalachians. Changes from the 
previous issuance were to elongate the previous slight risk farther
westward through the Lower Ohio Valley and southward into the
Southern Appalachians where heavy rains fell over the past 24 
hours. The eastern portion of the slight risk over west central NC 
was trimmed westward given relatively high FFG values and no precip
overlap potential from past 24 hours and the upcoming day 1 
period.

...Florida...
Concentrated the marginal risk area across the southern portion of
the peninsula where model consensus is for heavy rainfall in the 
high PW axis along and south of the stationary frontal 
boundary/trof currently analyzed off of the FL east coast. HREF 
neighborhood probabilities are high for 1, 2 and 3"+ amounts across
the southern half of the Peninsula, supporting isolated runoff 
issues, especially in the more urbanized regions.

...Southeast Arizona into southwest New Mexico...
No significant changes made to the marginal risk area across 
southeast Arizona into southwest New Mexico. Scattered convection 
likely again associated with shortwave energy rotating northward on
the western side of the Southern Plains upper ridge and across 
portions of the Southwest. There is the usual low confidence in qpf
details, but potential for isolated heavy totals and localized 
runoff issues. The marginal risk area fits well with the axis of 
the 1"+ HREF neighborhood probabilities.

Oravec


Day 2
Valid 12Z Tue Jul 30 2024 - 12Z Wed Jul 31 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE NORTHERN MID-ATLANTIC INTO THE CENTRAL APPALACHIANS...

There is not expected to be any significant changes to the overall
large scale flow across the northern tier of the country from the
Upper Mississippi Valley, east-southeastward across the Great
Lakes, Ohio Valley, Central to Southern Appalachians into much of
the east coast. West northwesterly mid to upper level flow will
again persist across these regions with additional embedded
shortwaves once again supporting potential for large regions of
convective activity. The lead area of height fall expected to
support potentially organized convection across portions of the
Central Appalachians into the northern Mid-Atlantic in an axis of
PW values 1.5-2.5 standard deviations above the mean. The previous
slight risk was expanded northeastward into the northern Mid-
Atlantic to cover this heavy rain potential. The southern portion
of the previous slight risk area was extended farther south into
eastern TN/far western NC to cover the area of qpf overlap day 1
and day 2. 

...Ohio Valley into the Upper Mississippi Valley...
To the west and northwest of the slight risk area, there is a lot 
of model qpf spread through the Ohio Valley into the Upper 
Mississippi Valley in the region where additional mid to upper 
level vort will be tracking east southeastward in a continued axis 
of above average PW values. To cover the model qpf spread, the 
previous marginal risk area was expanded significantly to the 
northwest into the Upper Mississippi Valley. At the moment, not a 
lot of confidence in any one heavy model qpf, so the risk level was
kept at marginal across these areas. 

...Southwest Florida...
The previous marginal risk area was decreased in size and 
concentrated over Southwest Florida. This corresponds to where the 
HREF neighborhood probabilities for the 12 hour period from 12Z Tue
to 00Z Wed are highest for 2 and 3"+ amounts. Isolated runoff 
issues possible, especially over urbanized regions.

...Southwest...
No changes expected to the large scale flow with the upper ridge 
remaining centered over the Southern Plains. This will again 
support shortwaves rotating northward on the western side of this 
ridge into the Southwest, supporting scattered convection, 
localized heavy rains and isolated runoff issues.

Oravec


Day 3
Valid 12Z Wed Jul 31 2024 - 12Z Thu Aug 01 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE UPPER MISSISSIPPI VALLEY INTO THE MID WEST...

The progressive northern stream flow will continue into day 3 with
the next strong area of height falls expected to push eastward
across the Northern Plains and into the Upper Mississippi Valley.
There is potential for additional organized convection/heavy
rainfall to push eastward with these height falls across eastern
portions of the Northern Plains and into the Upper Mississippi
Valley. There are some typical latitude differences with the max
qpf axis. The day 3 slight risk area was drawn to favor the more
southern solutions of the EC, NAM and CMC. The previous slight risk
area over the Upper Mississippi Valley was suppressed more to the
south and southwest to better match the more southern solutions
with the next round of potentially organized convection.

...Eastern New York State into western New England...
The strong height falls moving out of the Central Appalachians 
into the Northern Mid-Atlantic day 2, will progress across eastern 
NY State into New England day 3. There is a typical amount of qpf 
spread for the day 3 period, but general consensus for potential of
moderate to locally heavy rainfall amounts in a region of much 
above average PW values ahead of these height falls. A broad 
marginal risk area was maintained from the previous issuance to 
capture the heavy rainfall spread in the models across this area 
day 3.

...Southwest...
Similar to the days 1 and 2 period, the mid to upper level ridge
will remain centered over the Southern Plains. Scattered convection
again likely over portions of the Southwest as shortwave energy
again rotates northward on the western side of this ridge and into
the Southwest. Localized heavy rains and isolated runoff issues
again possible for southeast Arizona into southwest to central New
Mexico.

Oravec
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