071
FXUS63 KSGF 031140
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
640 AM 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.

- A Marginal (1 of 5) to Slight (2 of 5) Risk of Severe Storms
  exists this afternoon into tonight, for extreme south-
  central Missouri. Large hail will be the primary potential
  severe weather hazard.

- Slight (2 of 5) to Enhanced (3 of 5) Risk of Severe Storms
  Friday. All hazards will be possible with a conditional
  potential for hail greater than golf ball size, and a strong
  tornado or two in extreme south-central Missouri.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 345 AM CDT Thu Apr 3 2025

Infrared satellite and radar imagery depicts a large storm
complex still ongoing east of our area across the Ohio and Lower
Mississippi River Valleys. The extent of the complex is on the
east side--and parallel to--a 130-150 kt upper-level jet core
that`s spread from the TX panhandle up to northern MI. This jet
core has rather stalled out, allowing the associated surface
cold front to also slow its eastward progression. Though the
core of the jet has stalled, RAP analysis paired with mid-level
water vapor imagery depicts several bends or waves along the
extent of the jet, which culminates in a deep trough over the
west CONUS. These bends and waves will modulate over the course
of the next few days while the overall jet remains stationary.
This will bring our multiple rounds of heavy rain into the
weekend. For now, we`re in another calm period before
precipitation chances ramp up. Winds are calm with lows on track
to dip in to the middle 40s to middle 50s.


Multiple rounds of showers and thunderstorms begin today:

One of these modulations will occur today as mid- and upper-
level heights rise across our region ahead of an amplifying
mid-level shortwave. Lift from the shortwave, along with
synoptic support from right entrance region dynamics, will
increase the low-level jet overtop the surface front. This will
force widespread showers and some thunderstorms across our area
today. Onset of the first showers looks to be sometime during
the 6 to 10 AM timeframe, lasting through much of the day before
decreasing in coverage and intensity after midnight. Rainfall
amounts today do not look to be all that impactful with most
areas receiving 0.25-0.5 inches of rain by the end of this
round. Since some elevated thunderstorms can be expected,
localized areas may see higher amounts up to 0.75-1.00 inches as
depicted by HREF LPMM rainfall amounts.


Marginal to Slight Risk for extreme south-central Missouri today:

The best chance for thunderstorms will be later this afternoon
into the overnight hours as the HREF mean brings in 100-500 J/kg
MUCAPE in extreme south Missouri (like along and south of
Highway 76/160) after 5 PM, and gradually increasing through
the night. Determinist RAP soundings suggest perhaps some
earlier mention of thunder as they bring in 100-500 J/kg MUCAPE
after 1 PM. Either way, the instability will be enough for
thunderstorm development, and with lapse rates above the
inversion at 6-7 C/km, and more than enough unidirectional shear
(90 kts 0-6 km bulk shear; 40 kts effective), a few marginally
severe storms may occur in extreme southern Missouri. Since
these storms will be elevated, hail up to the size of quarters
will be possible. We will have to monitor the potential for
greater elevated instability, since there will be more than
enough shear for supercells. If an isolated supercell can
develop, hail up to the size of golf balls would be possible.

Cooler air behind the cold front along with widespread cloud
cover and rain will keep highs in the middle 50s to middle 60s
today. After showers and storms exit the area after midnight,
lows will dip into the upper 40s to lower 50s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 345 AM CDT Thu Apr 3 2025

Slight to Enhanced Risk for extreme south-central Missouri Friday:

After a brief lull in precipitation tonight, the next round will
commence as another amplification of the wave occurs. With the
trough axis shifting closer to our region and the downstream jet
becoming more meridional, this wave amplification is progged to
lift the surface inverted pressure trough further north into
southern Missouri. 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 Missouri,
bringing the threat for hail up to quarters, and up to golf
balls within any supercells.

The warm front is progged to setup along a line from Branson to
Salem by the afternoon. This will create a sharp gradient of
temperatures and dewpoints across the area with highs in the
middle 50s toward west-central MO, and highs near 70 in south-
central MO (near West Plains). Within the sector of near 70
temperatures south of the warm front, surface-based instability
could develop. The HRRR/RAP develop 1000-2000 J/kg of SBCAPE
within this region. If surface-based instability of this
magnitude is able to develop within our area, HRRR/RAP
hodographs are absolutely bonkers with a clean half-circle all
the way through the troposphere generating 30-40 kt 0-1 km bulk
shear, 400-500 m2/s2 0-1 km SRH, and 60-70 kt 0-6 km bulk shear.
This would easily be capable of producing significant tornadoes
within any discrete/semi-discrete supercell able to develop.
This may be difficult given shear vectors parallel to the forced
conglomerate of heavy rain and thunderstorms to occur Friday,
but this sort of look was seen in models for yesterday`s high
risk, and yet, numerous discrete supercells were able to develop
ahead of the line. Notably, an experimental CAM called the RRFS
consistently depicted the behavior and location of these
supercells almost spot-on up to 36 hours beforehand while all
other CAMs struggled to show the real solution until a few hours
beforehand. While the RRFS has been known to have its flaws,
that is an impressive feat. It is showing some of the same
behavior for Friday`s storms, so the ceiling for tornadoes is
certainly high if this scenario pans out.

The key word in this scenario is "could". The warm front is
progged to be just north of the border, leaving a thin sliver of
our area within the significant tornado probabilities. Any
wiggle of the front southward would effectively cutoff the
tornado threat and bring mainly elevated embedded supercells to
our area. Of course, on the flip side, a further northward
trending warm front would mean more of our area in the risk.
Since heavy rainfall in our area is bound to develop cold pools,
would err on the side of a further south warm front, but trends
will continue to be monitored. Bottom line is that there is a
risk for tornadoes, some potentially strong, south of the warm
front in the Enhanced (3 of 5) Risk. This is within Ozark,
Howell, and Oregon counties. Just along and north of the front,
instability will be more elevated, so hail up to golf balls or
greater will be possible with any established elevated
supercell.


Potentially significant flooding across south-central Missouri:

During the severe threat Friday, the aforementioned meridional
wave and lift will force a SSW-NNE oriented swath of heavy
rainfall and embedded thunderstorms that slowly moves east
through the day and into the night. NAEFS ESATs depict near
record PWATs surging into the region at 1.50-1.75 inches. The
EFI depicts 2 shifts of tails within values of 0.7-0.8 for QPF
amounts. This suggests a potentially impactful amount of rain
Friday into Saturday. Looking deeper, hi-res CAMs are depicting
this round to be on the more impactful end of the spectrum. NBM
24 hour precipitation from 7 AM Friday to 7 AM Saturday shows a
25th-75th percentile spread of 2-4 inches across south-central
MO, and 1-3 inches along and northwest of I-44. Our current
gridded forecast calls for 3-5 inches in south-central MO, and
0.5-3 inches along and northwest of I-44. HREF LPMM amounts for
this timeframe are concerning with depictions of multiple swaths
of 5-7+ inches across southern MO. This would occur in 24
hours. As such, rainfall amounts Friday into Saturday morning
look to be widespread areas of 2-5 inches (lower values toward
west-central MO), with localized amounts up to 5-8 inches within
areas that see multiple heavy thunderstorms. These kinds of
amounts in 24 hours will certainly pose the risk for flash,
river, and areal flooding, perhaps significant. River forecasts
are already taking some areas into Moderate Flood Stages with
HEFS output suggesting a currently low-end chance of some rivers
reaching Major Flood stage (10-20% chance).

The rain doesn`t end 7 AM Saturday, though. The wave will
amplify across our region one last time as the trough axis
finally starts translating east. This will force our last round
of showers and thunderstorms Saturday morning through the
evening. NBM spreads point to widespread amounts of 1-2.5 inches
along and southeast of I-44. The 90th percentile for this
timeframe is in the 2-4 inch range, thus we could see an
additional 1-2.5 inches of rain with localized values up to 2-4
inches from Saturday 7 AM to Sunday 7 AM.

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 inches. While we
would like to be conservative in our forecasts as not to raise
too many alarms too early, the trend for localized values of 5-8
inches from HREF LPMMs Friday (in addition to West Plains seeing
1.5 inches of rain from this last round of rain), does raise
caution into what absolute maximum localized values could be. As
an absolute worst case scenario, some localized areas may see
up to 10-15 inches of rain come Sunday morning. For now, a
reasonable worst case scenario would be localized values up to
9-10 inches. 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 /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 640 AM CDT Thu Apr 3 2025

A brief period of calm VFR conditions will prevail through
12-14Z. Afterwards, widespread rain showers and thunderstorms
will move into the area for much of the period (60-90% chance).
It`s difficult to pinpoint exactly when lulls and the heaviest
precipitation will be, so have included TEMPOs for much of the
time to signify that there will be periods of heavier showers as
well as periods of no showers at all. The bottom line is that
through the whole period, widespread rain/showers will be in and
around the area. The best chance for thunderstorms will be
after 18Z as elevated instability increases across the area.
There is the low-end potential (5% chance) for some
thunderstorms to produce small hail up to quarter size,
especially at BBG.

Otherwise, cigs will slowly deteriorate to MVFR through the
period as winds stay modest out of the east. These should then
decrease to IFR by 22-01Z, with a chance of LIFR cigs towards
the end of the period. With <30% confidence on this timing, set
at OVC006 for now, but note that lower cigs after 06Z is
possible.

Within the easterly winds, some gusts up to 20-25 kts may
occur, but rather infrequently.

&&

.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>092-095>098-102>106.

&&

$$

SHORT TERM...Price
LONG TERM...Price
AVIATION...Price
HYDROLOGY...Price