Monday, April 29, 2019

Monday -  Cloudy with thunderstorms ending before noon. High: 66-70.

Monday Night - Cloudy with thunderstorms developing after midnight. Low: 56-60.


Tuesday - Cloudy with thunderstorms. Storms may be severe, especially after noon. Storms may produce heavy rainfall. High: 70-74.

Tuesday Night - Cloudy with thunderstorms ending by dawn. Storms may be severe, especially before midnight. Storms may produce heavy rainfall. L: 60-64.

Wednesday - Mostly cloudy with scattered thunderstorms possible, mainly during the afternoon. Storms may be severe. High: 76-80.  

Thanks to for the icons!

Very active weather is in store for central Missouri over the coming days. A frontal boundary currently set up over Missouri will move very little between now and Wednesday, and it will act as the focus for several rounds of showers and thunderstorms during this period. Between Tuesday and Wednesday, there will be a heightened risk of severe thunderstorms, with large hail and damaging winds being the main threats. Additionally, any thunderstorms will have the potential to produce torrential rainfall, and with several rounds of thunderstorms in store, localized flooding is possible.

Forecasters: Travis, Ritter, and Hirsch
Issued: 10:30 a.m., 29 April 2019

Technical Discussion (The nerdy stuff we are discussing in class!)
A very active weather pattern is setting up over mid-Missouri. With it will come the threat of heavy rain, thunderstorms with the potential for severe storms. As per WPC's recommendation of a non-NAM model blend, went primarily with GFS and SREF guidance due to their coverage of the entire period. For short term CAMs, went with the HREF ensemble. The main issue with this active period is analyzing the threat for severe weather and flooding across the state. 

Monday morning, radar showed a line of heavy rain moving east through the state, exiting Columbia shortly after 12z. Behind it, GOES IR imagery shows partial clearing over the eastern half of the state and sky cameras from KRCG 13 back this up. This shot of sunshine will allow our temperatures to surpass what 06z model output suggested. For this reason, we went slightly higher with Monday's high than model guidance suggests. As the sun comes up, we now have GOES VIS imagery available. Visible satellite suggests that this partial clearing will not stick around for long. As this line moves further off to our east, the chance for precip later in the day diminishes. Looking at paintball plots of >40 dBZ from the HREF, some members plot isolated showers to our south in the Missouri Ozarks. However, looking at the current surface map from the WPC, the cold frontal boundary to our west and the stationary front well to our south in Arkansas should keep this precip to our south. 

Monday Night, our chances of precipitation return. At 250 hPa, the GFS has an area of strong divergence moving northeast into Missouri at 06z Tuesday. As the night progresses, divergence intensifies and becomes more widespread over central Missouri. Stepping down to 500 hPa, the GFS has a small, but intense vorticity maximum propagating into mid-Missouri. This will follow the general flow as Missouri sits in the inflection point of the 500-hPa trough to our west and ridge to our east. Overnight Monday, moisture and lift is on the increase according the GFS 700-hPa hgt, RH, and omega. This is all due to a strong LLJ analyzed at 850 hPa. After briefly quieting down during the day Monday, the LLJ ramps back up at 06z Tuesday. Maximizing over mid-Missouri at 50 knots Tuesday night into Wednesday. This will bring more than enough warm moist air from the Gulf of Mexico, into the Midwest to fuel thunderstorm development. The GFS Skew-T at 06z Tuesday shows a completely saturated layer from 700 hPa down to the surface, with negative omega existing at this saturated layer. This, combined with 928 J/Kg of MUCAPE, leads to likely rumbles of thunder throughout the night. 

Tuesday, the potential for showers and thunderstorms remain. GFS Skew-Ts show brief drying of the PBL after 18z. We stay dry until after 00z when a fully saturated column with ample lift returns. Again, thunderstorms over night Tuesday appear likely, with well over -10 ubar/s of lift depicted by the Skew-T at 06z. The most unstable parcel also drops considerably from Monday night, lifting from ~925 hPa, making surface based convection all the more likely. 

Wednesday day, we see an impressive set up for severe convection. As soon as the sun comes up on Wednesday, the atmosphere wastes no time destabilizing. GFS Skew-T for 12z Wednesday already have characteristics of a "loaded gun" with a warm moist surface, lift at the surface, and 850-500-hPa lapse rates of -7.3 C/Km. Surface based CAPE is valued at 929 J/Kg with CIN of 80 J/Kg. One issue mid-Missouri might face is the potential for thunderstorms firing too early in the morning. By Wednesday afternoon it is likely there will already be widespread thunderstorm activity. By 00z Thursday, soundings show a surface based CAPE of 2900 J/Kg with no CIN. The Bulk Richardson number at this timestep is 114. The extremely high CAPE, and low shear will make it harder for supercellular activity to thrive, at least over mid-Missouri. What appears more likely is a strong QLCS taking shape over Missouri possibly bringing with it, strong winds and hail. The SPC has Columbia just outside of a slight risk for Day 3. Seeing as this is a Wednesday afternoon event, the potential for severe is still up in the air. Will defer to later shifts to analyze the specifics, and the threat going forward into this week.

The threat of flooding persists with this system as well. GEFS mean of QPF favors the potential for over 3 inches of rain by the end of our period. SREF is lower, favoring only about 2 inches. Regardless, both scenarios will have the potential to result in messy flooding across the state. LSX already has Boone County under a hydrologic outlook. Again, will defer to later shifts to better narrow down the flooding threat as the week progresses. 

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