Sunrise 6:01 AM   Sunset 7:45 PM Moonrise 12:00 AM   Moonset 8:03 AM

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FXUS63 KLSX 270423 AFDLSX

Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1123 PM CDT Fri Apr 26 2024

KEY MESSAGES

-Showers and a few thunderstorms are expected to continue to move across the area through this evening. A few of these storms could produce locally heavy downpours and gusty winds.

-Showers and thunderstorms are likely over the area on Saturday and Sunday. A few severe thunderstorms are possible over western parts over the area on Saturday and across the entire area on Sunday. Large hail, damaging winds, and an isolated tornado are possible with the strongest storms as well as a localized flash flooding threat.



SHORT TERM
(Through Sunday)
Issued at 428 PM CDT Fri Apr 26 2024

A band of showers and scattered thunderstorms is moving northeast across the CWA this afternoon ahead of a shortwave trough with a band of low level moisture convergence moving northeast across Missouri and Illinois. The latest run of the HRRR and other CAMS are showing this batch of rain continuing to move northeast across the CWA through the early evening before it exits the CWA There is also a low chance (<30%) that storms now developing over eastern Kansas will hold together and enter central and northeast Missouri late this evening, though only the NAMNest is showing this possibility. Otherwise, we have stayed well north of the warm front today in the cool air and the SPC objective analysis is showing most of the CWA with MUCAPES of 100 J/kg or less. Expect most storms to stay below severe limits because of this lack of instability.

Additional showers and thunderstorms will be possible during the day on Saturday, though the coverage is not expected to be as extensive as a shortwave ridge will be building as it moves across the area.
The best chances (around 50%) will be across southeast Missouri into southwest Illinois where a weak mid-level impulse will combine with 925-850mb moisture convergence to bring a chance of showers and thunderstorms. Another area will be across northeast Missouri into west central Illinois which will be closer to a surface front with little capping. There will be an increased chance for showers and thunderstorms Saturday night into Sunday as another shortwave trough rounds the Great Plains upper low and increases mid-level lift at the same time that the low level jet increases in speed on Saturday night. Expect to see a gradual increase showers and thunderstorms that will move into the area from the west on Saturday night. This will continue to move east across the day on Sunday as both the NAM/GFS are showing a maximum in mid-level ascent/low level moisture convergence moving across the the CWA This goes along well with the LREF showing a band of high probabilities (>90% for 0.01" precip)
moving across the CWA from Saturday night into Sunday night in concert with the NAM/GFS forcing. A few severe thunderstorms remain possible mainly during the late afternoon and evening hours when heating will be maximized. Saturday's threat will mainly be over the western part of the CWA and be limited somewhat by weaker deep layer shear compared to Sunday which will cover much of the CWA and have stronger deep layer shear. While most of the global models show the shortwave trough moving across Missouri and Illinois during the evening and early overnight hours, the surface front does not move into the area until Monday.

Britt

LONG TERM
(Sunday night through Next Friday)
Issued at 428 PM CDT Fri Apr 26 2024

Global models are showing the front getting hung up over Missouri and Illinois next week in quasi-zonal flow aloft. There will be some instability available along the front which will allow showers and thunderstorms to develop along it each day. CIPS and CSU guidance are showing some low probabilities for a few strong to severe thunderstorms over the area into next week. Temperatures will remain above normal as 850mb temperatures will be in the 10-15C range.

Britt

AVIATION
(For the 06z TAFs through 06z Saturday Night)
Issued at 1119 PM CDT Fri Apr 26 2024

Isolated showers and thunderstorms will continue to be possible across much of the area through the period. The most likely times will be right at the beginning of the period from 06Z to around 10Z, then again on Saturday afternoon/early evening. Did not mention thunder in this TAF cycle due to the timing uncertainty and likely low coverage of storms. Otherwise, VFR ceilings which will occasionally scattered out at times and southerly flow gusting up to 25-30kts is expected to prevail. There will also be a few patches of MVFR ceilings early in the period, mainly across central and northeast Missouri.

Carney

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

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