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wxman22 wrote:Nothing has changed. The latest WPC forecast and NBM below.
https://i.ibb.co/n8PD01F9/wpc-qpf-168h-p-us-sc-2.png
https://i.ibb.co/VccwL02L/qpf-acc-imp-us-sc-1.png
Brent wrote:Now the NAM has a crashing cold front here Saturday morning with temperatures falling into the 40s![]()
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wxman22 wrote:Chances of seeing 2 inches or more. Models are hinting that there may be training storms along the stalled frontal boundary around the I-44 corridor. The WPC has also increased QPF here.
https://i.ibb.co/TMS5XydV/IMG-0348.png
https://i.ibb.co/d0L7Z1Gz/IMG-0349.png
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
808 PM EDT Thu Apr 17 2025
Day 3
Valid 12Z Sat Apr 19 2025 - 12Z Sun Apr 20 2025
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM EASTERN
OKLAHOMA THROUGH MUCH OF SOUTHERN MISSOURI...
20Z Excessive Rainfall Discussion Update...
The 12Z suite of model guidance largely supports the placement and
amounts of QPF..although there has been a subtle westward shift
over the course if the past few model runs...especially noticeable
from parts of northeast Texas/southeast Oklahoma into Arkansas.
Trimmed a bit territory from outlook areas in this
region...although did not want to remove given the propensity for
convection to build into the deeper moisture and instability south
of the front with time even though the model QPF was focused in a
narrow channel. Pulled the southern end of the Moderate risk area
southward given the increase in WPC deterministic back towards the
Red River. Overall...the large scale synoptics have not changed
significantly so much of the previous discussion remains valid.
Bann
Previous Excessive Rainfall Discussion...
In coordination with the impacted forecast offices, a Moderate
Risk upgrade was introduced with this morning's ERO update. A
stationary front separating very warm and moisture-laden air to the
south from abnormally cold air to the north will stall out from
being a cold front in previous days. Weakening northeasterly flow
of cold, dry air on the north side of the front, spurred on by a
Canadian high over the Great Lakes will contrast with an ever
increasing supply of hot and humid air straight out of the Gulf
being advected northward on up to 50 kt winds across Texas and into
the frontal interface from north Texas through Oklahoma and
Missouri. Meanwhile in the upper levels, a potent shortwave,
previously an upper level low will eject eastward out of the
mountains and into this warm and humid air mass. This will result
in cyclogenesis across Oklahoma by Sunday morning. Until that
happens though, the front will be largely stationary, with the warm
humid air tracking northeastward on one side, and cool, dry air
tracking southwestward on the cold side. The abundance of moisture
and cold pools from Friday night's storms will support continued
shower and thunderstorm development south of the front. As the
shortwave approaches, additional shower and thunderstorm
development will occur, and with stronger storms due to the added
forcing as the surface low develops to the west.
The southerly flow of humid air will cause the storms to run into
the Ozarks of Oklahoma, Arkansas, and especially southern Missouri
on Saturday. The mountains will further uplift the moisture,
resulting additional locally heavy rainfall. The Ozarks are known
for being particularly flash flood prone due to the mountains
helping funnel the water quickly into the river valleys, so this
prolonged period of heavy rainfall is likely to cause some of the
worst impacts to occur in these regions.
As the storms track northeastward across Missouri, the front is
likely to direct them into the St. Louis metro. In coordination
with LSX/St. Louis forecast office, the Moderate Risk's
northeasternmost extent includes the St. Louis metro. While the
storms may not be quite as strong as compared with areas further
south and west by the time they reach St. Louis, the urban corridor
and confluence of major rivers in the area may exacerbate urban
flooding concerns as repeated rounds of heavy rain likely move over
the city.
Some of the guidance (RRFS/UKMET/CMC) are favoring the southern end
of the ERO risk areas across Texas and Oklahoma as being the area
with the heaviest rain. Should that occur, then, the Dallas-Fort
Worth Metroplex will also be at higher risk for flash flooding, and
the Moderate Risk may need to be expanded southwestward with future
runs. There were 2 camps of guidance, largely split between foreign
and domestic, favoring the southern and northeastern ends
respectively. To account for these factors, the Slight and Marginal
Risk were expanded northeastward along the frontal interface to the
IL/IN border for the Slight, and well into northern Ohio for the
Marginal.
Wegman
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