Wednesday/Thursday Severe Weather situation

***SEVERE WEATHER LIKELY WEDNESDAY EVENING THROUGH THURSDAY AFTERNOON***

Update 11:30 AM - The Storm Prediction Center has issued a Tornado Watch for the area until 10:00 PM.

UPDATE (4/17 at 7:00 AM) - Latest model data continues to indicate potential for severe weather over east central MO. The first round should take place this evening, after 5:00 PM. The initial mode may be supercells capable of producing large hail, damaging winds, and isolated tornadoes.

A very concerning weather situation developing for the region from late afternoon Wednesday through late Thursday afternoon. A potentially significant severe weather situation is expected for the entire area as favorable severe weather parameters are forecast to develop over the next 24 to 48 hours.




Tonight, a warm front will move northward and will pass through the area Wednesday morning. Some showers and thunderstorms may develop overnight near this front. This front will bring warm and humid air back in to the area. A very warm and increasingly humid air mass will build through the day tomorrow. Thermodynamic instability will increase throughout the afternoon as temperatures reach 80 degrees and dewpoints rise through the 60's. There will be very little capping inversion to limit thunderstorm development. Moderate instability and favorable wind dynamics will combine to allow for strong to severe storms to form Wednesday evening and through the overnight hours. Some of these storms may be severe with large hail and damaging winds.
Thursday morning may be relatively dry with slightly more stable air from overnight rain. Temperatures should quickly rebound by late morning and even some sunshine will be possible. Any sunshine will help to create a fairly volatile environment as surface temperatures warm in to the 60's and the 70's by early afternoon. Low level moisture will be high and this combined with surface heating will contribute to a moderate to strongly unstable atmosphere.
As the cold front approaches from the west a very favorable wind profile will setup by Thursday afternoon. Very favorable directional wind shear accompanied by upper level diffluence (spreading air aloft) over MO (especially southwest of St. Louis) could create a situation that makes mature thunderstorms rotate becoming supercells that will be capable of very large hail and damaging winds. Also, these conditions combined with fairly favorable helicity parameters are indicating a chance that these supercells could become tornadic by Thursday afternoon over portions of MO and IL. A few strong tornadoes may be possible where these conditions are optimized. Supercells will likely consolidate in to a squall line by Thursday evening and will eventually move east of the area.





Stay tuned for later updates as new data becomes available.

--JK

Severe Weather possible today and tonight

The chance of showers and thunderstorms will increase by this afternoon.Conditions will be favorable for the development of severe storms that will be capable of large hail, damaging winds.

Severe Weather Outlook (May 3 - 7)

For the St. Louis metro area:

 Thursday May 3 – A slight chance of scattered thunderstorms by late evening and overnight. Most of the activity today will be over the northern half of MO. Low chance of severe weather from I-44 southward. (Low does not mean zero)

 Friday May 4 – A chance of thunderstorms, a few storms possibly severe in the afternoon and evening.

 Saturday May 5 – (limited data) – A slight chance of storms, severe weather not currently likely.

 Sunday May 6 – (limited data) CF moves east. Severe weather possible. This activity may go in to Monday.

See preliminary Sunday outlined area : https://www.arcgis.com/explorer/?present=c08b353a1d6b416688cdaea8f5682525 (only one slide for now)

 Monitor the above dynamic map URL for later changes and updates as well as the St. Louis Weather Watchers sites. http://stlwxwatchers.blogspot.com/ (links to FB and Twitter linked here)

Slight Risk of severe weather for remainder of today

Today we will become moderately unstable by this afternoon (SBCAPE ~2500), but there isn’t any noticeable trigger for lift later in the afternoon per RUC or RR. But, the models do show some precip developing by late afternoon in the area. Wednesday and again Thursday afternoon and night is looking a little interesting with moderate to high instability, high dewpoints. Main jet energy will be further north. Supercells look possible, especially for western and northern MO. Main lift looks to still be north of here, but I’ll keep an eye on it. SPC just added us in to DY1 Slight for the rest of today…:-)