Severe Thunderstorm Warning 130, NWS St. Louis, MO

Area Forecast Discussion
National Weather Service Saint Louis MO
255 PM CDT Fri May 16 2025

.KEY MESSAGES...

- Severe thunderstorms are expected to continue until storms exit
  between 6 and 7 PM this evening.

- After a brief period of dry weather tonight - Saturday evening,
  the chance for rain showers and thunderstorms returns Saturday
  night into next week, with the highest chances on Monday night
  and Tuesday.

&&

.SHORT TERM...  (Through Late Saturday Night)
Issued at 248 PM CDT Fri May 16 2025

Isolated to widely scattered supercells have developed fairly
rapidly over the past couple of hours in our area along a fast-
moving cold front. This boundary is located just west of a
KVIH>>KUIN axis and should clear the southeastern CWA by or just
before 2300 UTC. Large hail, potentially very large (2.75+") still
looks like the main threat given very steep midlevel lapse rates
and associated hail CAPE. The tornadic potential increases with
southerly extent, with the latest SPC mesoanalysis showing 0-1km
SRH around 150-175 m^2/sec^2. LCL values are also a bit lower down
in southeast Missouri and southwest Illinois compared to east-
central Missouri and south-central Illinois. However, a strong RFD
surge very recently just helped spin up a tornado further north,
so the threat continues across the entire tornado watch.

Much cooler and drier air will filter into the area behind this cold
front. Therefore, look for dry weather the remainder of tonight into
Saturday evening along with temperatures much closer to seasonal
normals.

Gosselin

&&

.LONG TERM...  (Sunday through Next Friday)
Issued at 248 PM CDT Fri May 16 2025

(Saturday Night - Tuesday Night)

Today's cold front is expected to stall out across the mid south and
then begin to move back northward as a warm front late this weekend
into early next week. Multiple rounds of showers and thunderstorms
are expected mainly along/north of this retreating boundary through
early next week. There still appears to be 2 MCSs that may impact
the region, one Sunday night/Monday morning and another Monday
night/Tuesday morning. The latter should be further north than its
predecessor, but how far north is a question mark. Sometimes
antecedent convection really hampers the poleward progress of
retreating warm fronts. There is some modest lesside cyclogenesis in
the central Plains, which would argue for continued northward
movement, but again, this could be offset by the aforementioned
convection. The main focus through Tuesday morning likely will be on
heavy rain potential and flash flooding. Convection through that
time likely is to be focused along/north of the boundary and
elevated in nature (hail could be a threat though). In terms of
rainfall potential, the probabilities have trickled up about 10% for
2+" of total rainfall through Tuesday night. Chances are now in the
50-70% range across the bi-state area. For at least 4", chances are
in the 10-15% range, still quite low but a bit higher than yesterday
by about 5% on average. The overall concern for any significant flash
flood threat or river flood threat is still fairly low, but we will
have to keep an eye on this period for hydrologic impacts. As talked
about yesterday, a lot of the area is now running a slight deficit
in the rainfall department since May 1st. Parts of northeast
Missouri and west-central Illinois have fairly widespread abnormal
dryness/moderate drought conditions and could really use 2-3+" of
rain.

At least a conditional severe threat is still on the table for
Tuesday ahead of the midlevel synoptic trough and associated cold
frontal passage. Major caveats continue including a lot of spread
with the track/strength/timing of the trough itself and on
instability. The amount of instability remains a big question mark
due to antecedent convection primarily.

Temperatures during this time period still are tricky, especially
daytime highs. The track of each nocturnal MCS will have
ramifications on daytime highs both Monday and Tuesday. Not
surprisingly, the inter-quartile range from the NBM each of these
days is large, mainly on the order of 8-12 degrees in most
locations.

(Wednesday - Next Friday)

The mid/late week period continues to look increasingly chilly for
late May standards as an anomalous mid/upper level low slowly slides
across the Great Lakes. Temperature anomalies at 850 hPa peak out at
around 6 to 8C below normal Wednesday night across the area. While
those type of values wouldn't be noteworthy in the middle of winter,
it is for late May (closer to 2 sigma below normal). The coolest day
is likely to be on Wednesday, as highs in the 60s are forecast. If
clouds and/or rain continues across portions of the area, cannot
rule out some locations staying in the 50s. Lows late week are
dependent on the timing of the surface ridge and sky cover, but
widespread lows in the 40s are certainly on the table.

Gosselin

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1210 PM CDT Fri May 16 2025

Isolated to scattered thunderstorms will develop along a cold
front over the next couple of hours. The metro terminals still
have the best chance, but coverage is too low to be confident
enough to introduce a prevailing or a TEMPO. Any thunderstorm that
does directly impact a terminal would have the capability of
producing low visibilities in heavy downpours and large hail with
some wind threat as well. Storms will move off to the east
quickly, with dry weather and VFR conditions favored thereafter.
Winds are expected to veer through this evening, with
west/northwest winds behind the front. Gusts may diminish or at
least weaken this evening before picking back up again by mid
morning on Saturday.

Gosselin

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

WFO LSX

Hazardous Weather Outlook
National Weather Service St Louis MO
306 PM CDT Fri May 16 2025

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-172015-
Greene IL-Macoupin IL-Montgomery IL-Bond IL-Fayette IL-Clinton IL-
Marion IL-Washington IL-Randolph IL-Adams IL-Brown IL-Pike IL-
Calhoun IL-Jersey IL-Madison IL-Saint Clair IL-Monroe IL-Knox MO-
Lewis MO-Shelby MO-Marion MO-Monroe MO-Ralls MO-Pike MO-Boone MO-
Audrain MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO-
Lincoln MO-Gasconade MO-Warren MO-Saint Charles MO-Franklin MO-
Saint Louis MO-Saint Louis City MO-Jefferson MO-Crawford MO-
Washington MO-Saint Francois MO-Sainte Genevieve MO-Iron MO-
Madison MO-Reynolds MO-
306 PM CDT Fri May 16 2025

This Hazardous Weather Outlook is for portions of eastern and
central Missouri as well as west central and southwest Illinois.

.DAY ONE...Tonight.

Severe thunderstorms will continue through early this evening across
parts of east central and southeast Missouri into southwest and
south central Illinois. Very large hail in excess of 2 inches in
diameter, damaging wind gusts in excess of 80 mph, and a few
tornadoes are all possible.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Thunderstorms are possible again late Saturday night through next
Tuesday.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report any hail or wind damage to the
National Weather Service in St. Louis.

Gosselin

Preliminary Local Storm Report
National Weather Service St Louis MO
314 PM CDT Fri May 16 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0250 PM     Tstm Wnd Dmg     1 NW Saint Louis        38.65N 90.26W
05/16/2025                   St. Louis City     MO   Public

            4-foot diameter tree down at McPherson
            Avenue and Taylor Avenue.

&&

MF

Preliminary Local Storm Report
National Weather Service St Louis MO
318 PM CDT Fri May 16 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0241 PM     Tstm Wnd Dmg     1 WNW Saint Louis       38.64N 90.26W
05/16/2025                   St. Louis City     MO   Trained Spotter

            Numerous trees down across the area.

&&

Pfahler

Preliminary Local Storm Report
National Weather Service St Louis MO
319 PM CDT Fri May 16 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0251 PM     Tstm Wnd Dmg     1 SW Granite City       38.70N 90.14W
05/16/2025                   Madison            IL   Trained Spotter

            Damage in the area including trees and a
            snapped flag pole.

&&

Pfahler

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