-- Discussion containing changed information from previous version are highlighted. --
917
FXUS63 KSGF 171020
AFDSGF

Area Forecast Discussion
National Weather Service Springfield MO
520 AM CDT Mon Jun 17 2024

.KEY MESSAGES...

-  Heat and humidity will continue through today, then return
   late this week.

-  15-30% chances for isolated to scattered showers and
   thunderstorms east of Highway 65 today and Tuesday.

-  Breezy conditions Tuesday with southerly wind gusts up to
   25-30 mph, especially west of Highway 65.

-  Signal for above normal temperatures to continue through the
   rest of June.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
Issued at 400 AM CDT Mon Jun 17 2024

Current mesoanalysis puts our area in a region of weak upper-
level flow as a building upper-level high sits over the
Carolinas, and a longwave trough continues to churn out
shortwaves over the north and NW CONUS. Water vapor reveals a
shortwave/tropical disturbance lifting through the Mississippi
River Valley in LA/AR/MS. A ribbon of cirrus clouds associated
with this wave is barely reaching into our eastern counties. At
the surface, lee cyclogenesis is underway across the Colorado
front range. In response, the pressure gradient across the
Plains is tightening which has increased winds across our area.
Current obs at Springfield and Joplin have winds gusting above
20 mph at times tonight. Additionally, the winds have kept
boundary layer mixing up a bit, allowing temperatures to stay in
the middle to upper 70s. These are expected to drop onto the
lower to mid-70s by daybreak.


Heat and humidity will continue today:

The hot and humid airmass will continue to be in place today
underneath the western edge of the building upper-level high.
Highs are forecast to be in the lower 90s with dewpoints
continuing to be in the lower 70s. While this will generate Heat
Indices between 95-100 F, showers and thunderstorms east of
Highway 65 and winds picking up along the Ozark Plateau and
west of Highway 65 may make the heat and humidity a bit more
tolerable. Nevertheless, continue to practice appropriate heat
safety by taking frequent breaks if outside for extended periods
of time, and staying cool and hydrated.

Increased cloud cover and lower 850 mb temps associated with
tropical shortwaves coming up from the Gulf will temper the heat
and humidity a little bit into Tuesday with highs in the middle
to upper 80s and Heat Indices in the 90-95 F range. Lows Monday
and Tuesday night will continue to be mild, though, with
temperatures in the upper 60s and lower 70s.


15-30% chances for isolated to scattered showers and
thunderstorms east of Highway 65 today and Tuesday:

The aforementioned tropical shortwave disturbance (whatever you
wanna call it) will continue lifting NNE through today. Positive
vorticity advection associated with the wave should provide
enough lift for isolated to scattered showers and thunderstorms
to develop this afternoon. These would develop near the lobe of
vorticity, making the better chances for rain (20-40%) east of
Highway 65. There are a select few CAMs that do initiate some
storms into the Springfield and Branson area (10-20% chance),
though confidence is low in this scenario as the combo of the
greater axis of moisture (1.5-2" PWATs) and synoptic lift is out
east. Within this axis, NAEFS and ECMWF ESATs are progging
>99th percentile mean specific humidity through at least 850 mb.
With this much moisture, and the tropical nature of the wave,
brief, heavy downpours and lightning will be the main hazards
with these storms.

This pattern will continue into Tuesday with PWATs slightly
increasing to 1.75-2" east of Hwy 65 (97.5th percentile for this
time of year). Generally, the same chances of isolated to
scattered showers and thunderstorms exist for Tuesday afternoon:
20-40% chances east of Hwy 65, and a 10-20% chance along Hwy 65,
including the Springfield and Branson area.


Breezy conditions Tuesday with S`ly wind gusts up to 30-35 mph:

The surface pressure gradient across the Plains will continue to
tighten Tuesday ahead of a cold front traversing the northern
Plains. This will increase S`ly wind speeds across our area,
especially west of Hwy 65 closer to the stronger pressure
gradient. Sustained winds are forecast to be at 10-20 mph with
gusts up to 20-30 mph (higher speeds to the west). The NBM does
display a 20-40% chance for periodic gusts above 30 mph west of
Hwy 65 and north of I-44.
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&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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Issued at 400 AM CDT Mon Jun 17 2024

A note about showers and thunderstorm chances Wednesday:

Rain chances have been steadily dwindling from forecast to
forecast Wednesday. However, from a conceptual model, at least
some isolated showers and thunderstorms should be possible
around the area. As of right now, the greatest chances are over
our west-central MO counties (10-15%) ahead of a surface cold
front that is forecast to stall over KS/north MO. A deep dive
into the data reveals a potential reason why storm chances
dwindle across the rest of our area. An inverted trough
associated with a deeper tropical disturbance is forecast to
trek into central TX during the day Wednesday. This may
translate to the surface with a weak inverted trough/surface
low, which would promote surface winds across AR and south MO
to shift to ENE`ly while winds across central MO would continue
to be S`ly, feeding into the surface low in MN/IA associated
with the cold front. This would create large-scale surface
diffluence in our CWA, which could keep anything from
initiating. However, an isolated shower and/or thunderstorm
cannot be ruled out Wednesday. Nevertheless, highs Wednesday
will be in the middle to upper 80s and lows in the middle to
upper 60s.


Heat and humidity return late week:

After the brief "cooldown", the tropical disturbance will
dissipate off to the west and the trough across the north will
flatten. This will allow the upper-level high to really start
building westward into our region. NAEFS and ECMWF ESATs are
continuing to forecast record high geopotential heights at 200
and 500 mb reaching into SW MO Wednesday through Sunday (by
record high, that is within the 30-year climatology for mid-
June, not all- time). This will allow another wave of prolonged heat
to develop. Despite the high geopotential heights, 850 mb
temperatures will not exactly be anomalous, so record high
temperatures will not be challenged. Nevertheless, highs will be
in the lower to middle 90s Thursday through Monday with lows in
the upper 60s to lower 70s. Somewhat drier air (dewpoints in the
mid-60s) will limit rain chances during this period as well as
tempering Heat Indices a bit (mainly in the mid-90s). It will be
important to once again practice heat safety during this period.

There is a signal in models and ensembles for a front to come
through sometime this weekend, which would bring our next round
of more widespread rain chances, though model spread is too high
at the moment to say anything definitive.


Signal for above normal temperatures to continue through June:

The WPC continues to have us in a signal for above normal
temperatures for June 24th to 30th (50-60% chance). While this
does not lock us in for above normal temperatures all the time
through June, there is a good chance we stay above normal for a
majority of the time through the end of June. While there is
above normal temperatures forecast, there is also a semi-weak
signal for above normal precipitation as well, so drought-
inducing conditions are not exactly expected at this time.
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&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
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Issued at 520 AM CDT Mon Jun 17 2024

VFR conditions will prevail at all TAF sites until at least 19Z.
There is a 15-30% chance that bands of isolated showers and
thunderstorms make their way into SGF and/or BBG between
19-01Z, though these will more likely stay east of the area.
Otherwise, skies will remain mostly clear with only a few high
clouds throughout, and 5 kft cumulus between 18-01Z. S`ly winds
will pick up again this TAF period with winds up to 15-20 kts
and gusts up to 20-30 kts, especially at JLN. 40 kt low-level
wind shear may reach into JLN as a nocturnal low-level jet
strengthens between 04-08Z.
-- End Changed Discussion --

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
KS...None.
MO...None.

&&

$$

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