156
FXUS63 KSGF 032244
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
544 PM CDT Thu Apr 3 2025

.KEY MESSAGES...

- High confidence in multiple rounds of heavy rainfall through
  this weekend. Increasing confidence in this resulting in
  potentially significant flooding, especially in south-central
  Missouri. Friday into Saturday look to be the most impactful
  days. A Flood Watch is in effect along and southeast of
  Interstate 44.

- A Marginal (1 of 5) to Slight (2 of 5) Risk of Severe Storms
  exists into tonight, for portions of far southern Missouri.
  Large hail will be the primary potential severe weather
  hazard.

- Slight (2 of 5) Risk of Severe Storms Friday. Large hail will
  be the primary potential severe weather hazard. A conditional
  risk for a tornado or two. Remaining uncertainties in the
  severe potential.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 325 PM CDT Thu Apr 3 2025

A large upper-level trough is setup across the desert southwest
with a broad jet extending from the Southern Plains through the
Great Lakes region. A stalled surface boundary has settled south
of the jet, extending from the Red River Valley through the
lower Ohio Valley. Deep southwest flow will remain prevalent
into the central CONUS, with waves of energy riding along this
boundary. Strong low-level support from a 40-50 knot low-level
jet (LLJ) pumps continuous moisture into the area with PWATs
approaching 1.2 to 1.5 inches. Our area remains on the cold
side of the stationary boundary for the most part, as it wobbles
back and forth over the next 48 to 72 hours. This setup,
similar to that of the Maddox Heavy Rainfall Pattern, sets the
stage for multiple rounds of heavy rainfall and significant
flooding across the area this weekend.

Radar imagery depicts the first round of showers and thunderstorms
overspread the Ozarks region this afternoon. Coverage has
largely been focused along and north of Interstate 44 through
this morning, with scattered activity gradually increasing into
southern Missouri. This environment through this afternoon and
evening remains supportive of a few isolated strong to severe
thunderstorms. This is characterized by the presence of elevated
instability around 250-500 J/kg in the vicinity of mid level
lapse rates of 6.5 to 7.0 C/km. Meanwhile, unidirectional deep
layer shear (0-60km) on the order of 80-90 knots may help
organize a few of the updrafts. This setup will support elevated
hail producers, up to quarter sized or smaller. Pockets of
higher instability may support slightly bigger hail size, though
confidence remains low. SPC has maintained a Marginal (1 of 5)
to Slight (2 of 5) Severe Weather Risk south of Interstate 44
towards the MO/AR border to account for this potential.

From a rainfall standpoint, this initial batch of rain in
addition to yesterday`s act as primer for potential significant
flooding into the weekend ahead. The Flood Watch has been
expanded to include a few additional counties in southwest MO,
and is in effect through Saturday evening. CREST soil moisture
analysis depicts some bands of localized higher saturation
around 40-60%, with most areas drier around 25 to 40%
saturation. Rainfall amounts with this first round of activity
have ranged from a 0.25 to 0.75 inch in most locations, with
localized higher amounts around an inch or so. An additional
0.25 to 0.50 inches can be expected as activity lingers across
the Ozarks through the evening. A lull in the activity is
expected through the overnight activity as the initial wave of
rain lifts east of the area, outside of a few elevated cells
that many fester across south central MO.

&&

.LONG TERM /FRIDAY THROUGH THURSDAY/...
Issued at 325 PM CDT Thu Apr 3 2025

The next widespread round of begins on Friday morning as wave
amplification is progged to lift the surface inverted pressure
trough further north into southern MO. During the morning hours,
the 850 mb warm front will lift through the area at the nose of
a 30-40 kt low- level jet. At the nose of this LLJ, an arc of
thunderstorms will likely develop as convergence along the LLJ
nose taps into 500-1000 J/kg of uncapped instability in the
850-800 mb layer. Once again, shear will be plentiful, so a few
elevated strong to severe storms may develop and lift through
southern MO. Once again, hail up to the size of quarters would
be the primary hazard.

By the afternoon, guidance depicts a warm front lifting near the
MO/AR border. Recent trends suggest the warm front may struggle
to make it any further north than this, with the highest
potential for strong to severe thunderstorms progged to occur
along and just south of the front. However, there is still some
uncertainty with how this plays out. While storm motion is
expected to keep most of the activity on the cool side of the
boundary across southern MO, a few thunderstorms may be able to
tap into rich low-level moisture just along the boundary. For
this reason, SPC has maintained a Slight Severe Risk (2 of 5)
along and south of Interstate 44, with an Enhanced (3 of 5) to
Moderate (4 of 5) Risk draped into northern AR. Temperatures
will vary across the area, with highs from middle 50s (north) to
middle 60s (south). Dewpoints push into the lower to middle
50s. Ample buoyancy (~1500 J/kg) and shear (0-6km 60-70 knots)
will be present, to support at least a few scattered organized
thunderstorms across southern MO. Large hail (up to golf balls)
remains the primary risk, given a more likely scenario of
elevated supercells embedded within a potentially messy storm
mode. Damaging wind gusts will be tougher to come by in an
elevated thunderstorm, though the risk is not completely zero.
Meanwhile, the tornado risk is heavily tied to where the front
lies. An environment just south of the front, remains favorable
for tornadic development, potentially strong. This is supported
with ample low-level (0-1km) shear of 30-40 knots and 0-1km SRH
of 400-500 m2/s2. Thus, supporting tornadoes within surface
based supercells. However, the tornado risk has been nudged
south with the latest trends of the warm front. As a result,
confidence is low in the conditional tornado risk at this time.

The main attention turns towards the increasing confidence in
significant flooding to impact the area though Friday and the
remainder of the weekend. PWATs are progged to push closer to
1.5 to 1.8 by Friday and Saturday, with the EFI showing 2
shifts of tails within values of 0.7-0.8 for QPF amounts. We are
expecting this activity to come in waves/rounds, almost
repeatedly with brief lulls from Friday morning through Saturday
evening. To set the stage, confidence remains highest for areas
along and south of Interstate 44 to see the highest rainfall
amounts through this weekend. This is the area highlighted in
the Flood Watch through Saturday night. In this area, HREF 48
hour Probability Matched- Mean (PMM) depicts rainfall amounts
pushing 3 to 5 inches, with localized amounts of 5 to 7 inches
through Saturday morning. A look at 24 hour Localized PMM
captures similar trends of several bands of 3 to 5 inches,
localized up to 7 inches. This would only capture the extent of
rainfall totals through Saturday morning. With that being said,
it is becoming increasing concerning that higher amounts towards
the 90th percentile of WPC QPF may verify in some locations
across south central MO. This would support Average Return
Intervals (ARIs) of 50 to 100 years. Additional rounds of
rainfall persist beyond Saturday morning into the evening/night.
Through the event, rainfall rates will likely be approaching 1
to 2 inches per a hour, with localized higher rates. As showers
and thunderstorms repeatedly track over the same areas, amounts
may quickly add up. Flash Flood Guidance may quickly be
exceeded, posing the risk for flash, river, and areal flooding,
perhaps significant. This timeframe of greatest concern for
significant flooding to unfold across south central MO is Friday
evening through Saturday morning, in which guidance has
consistently highlighted. Impacts may be similar to past
significant rainfall events in the Ozarks region, such as the
Late April 2017 Flood event. WPC Excessive Rainfall Outlooks
depict the significance, with Moderate (3 of 4) to High (4 of
4) outlooks across southern Missouri on Friday and an additional
Moderate outlook on Saturday.

When it`s all said and done, this brings widespread storm totals
of 3.5-8.5 inches, with higher values toward south central MO.
The 25th-75th percentile spreads continue to get tighter,
depicting increasing confidence in a range of amounts. As an
example, West Plains 25th-75th is 4.5-7.5 inches with the 90th
percentile suggesting localized values up to 9 or 10 inches.
For now, a reasonable worst case scenario would be localized
values up to 9-10 inches. It is still plausible that even
localized higher amounts are realized. That being said, this
amount of rain brings the potential for flash, areal, and river
flooding, with some areas perhaps seeing significant flooding.

Cooler behind this system with snow and frost/freeze potential:

The system will finally kick through Sunday, bringing deeper
trough across east and central CONUS, resulting in a short of
cooler air. Near freezing temperatures may enter the region as
the backside of the system is exiting which could bring some
light snow or a rain/snow mix Saturday night. At the moment, no
impactful accumulations are expected. But near freezing to below
freezing low temperatures Saturday night through Monday night
brings high confidence for frost/freeze headlines. Plan
accordingly for outdoor crops/plants. Highs will be cool during
this time as well with temperatures in the lower 50s Saturday
and Sunday.

Dry weather and a warming trend then commences through next week
with highs going from the lower 50s Sunday, to the lower 70s
Thursday. Lows will also increase from the upper 20s to lower
30s Monday night, to the upper 40s Wednesday night.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 544 PM CDT Thu Apr 3 2025

Periods of showers and some isolated storms are currently moving
across the area early this evening. The thunderstorm activity
will mainly remain south of I-44 and east of Highway 65 this
evening. This activity will begin to end from west to east this
evening with the rain ending across much of the area this
evening, a few linger showers and maybe a thunderstorm could
linger across far south central MO into the early overnight
hours but will end overnight. Ceilings will begin to lower with
IFR ceilings developing later this evening then occurring
through the day on Friday. Additional showers and a few storms
will move back into the area from southwest to northeast Friday
morning and continue at times through the day.

&&

.HYDROLOGY...
Issued at 345 AM CDT Thu Apr 3 2025

River Expectations and Forecasts:

Abnormally Dry or Drought conditions exist across much of the
CWA as evidenced by below normal soil moisture and normal to
below normal streamflow. Despite the relatively dry antecedent
moisture conditions coming into this event, forecast rainfall
amounts will be enough to saturate soils and generate rises on
area waterways.

RFC forecasts are showing significant rises to many rivers in
the Flood Watch area. Locations along the Jacks Fork and Current
River are currently expected to reach Moderate flood stage.

Further north, the Gasconade River and some major tributaries
are also expected to exceed flood stage with the Big Piney
expected to reach Moderate Flood stage.

Further west, the James River is expected to rise approaching
or exceeding flood stage as well as the North fork White River.

Important Note: River Forecasts only include precipitation out
to 72 hours (Saturday morning) and additional accumulating
rainfall on Saturday may cause additional rises.

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
KS...None.
MO...Flood Watch through Saturday evening for MOZ070-071-081>083-
     090>098-101>106.

&&

$$

SHORT TERM...Perez
LONG TERM...Perez
AVIATION...Wise
HYDROLOGY...Perez