Monday, May 6, 2019

Tonight - Skies becoming cloudy. Thunderstorms developing after midnight. Storms may produce heavy rain. Low:58-62

Tuesday - Cloudy. Widespread thunderstorms during the morning and early afternoon becoming scattered during the late afternoon. Storms may produce heavy rainfall. High: 70-74

Tuesday Night - Cloudy. Scattered thunderstorms during the evening becoming more widespread after midnight. Storms may produce heavy rain. Low: 60-64

Wednesday - Cloudy. Thunderstorms likely during the morning, becoming scattered after noon. A few storms may be severe. High: 70-74

Thursday - Cloudy. Slight chance of thunderstorms in morning with showers around noon. High: 70-74   

Thanks to for the icons!

Better have the umbrella or rain jacket handy for the next few days because thunderstorm activity will dominate this forecast period. Narrowing down the timing of these individual storm events will be tough. It's also important to note flooding could occur on rivers over these next couple days. Tuesday into Tuesday night could see widespread heavy rainfall. Wednesday, we see the potential for strong to severe storms. The main threat with Wednesday will come in the form of damaging wind and hail overnight. Thursday shows morning thunderstorms with the potential for showers around noon.

Forecasters: Danaher, Browne and Hirsch
Issued: 5:00 p.m.; 6 May 2019

Technical Discussion (The nerdy stuff we are discussing in class!)

This forecast period will be quite eventful. WPC diagnostics recommends using a blend of the GFS
The WPC recommends using a blend of the GFS, and European models. For this forecast period, the GFS, NCEP SREF Plume and EMC GEFS Plume model were used because they were in between for the thunderstorms and precipitation over Columbia. The GEFS had higher values while the GFS had lower values with SREF in the middle.

Tonight shows good potential for rain around 03Z Tuesday to 12Z Tuesday. Anytime before this shows a clear dryness from the surface to 800mb. At 03Z Tuesday, GFS skew-T show CAPE values increasing from 838J/kg to over 1000 J/kg by 12Z Tuesday. Negative omega values at 3Z Tuesday are above 700mb with 15mb/s at 450mb, LI=-1, LCL=805mb, PW=1.39in. There is a dry slot shown on the 3Z Tuesday skew-T, but that is likely to moisten up throughout the rest of the night which leads to potential rain showers. The 09Z Tuesday shows similar results with CAPE increasing further into 900 J/kg, and negative omega at 850mb to 700mb around 1-3mb/s. Though this is not much forcing for ascent it does still have implications on how Tuesday will proceed and does provide a greater likelihood of thunderstorms.

Indeed, this storm continues showers into Tuesday and Tuesday night. This happens because the low-pressure system on the exit region of the ULJ north of Missouri and with no other jet to support it continues slowly across Missouri. One jet that will have an impact later is the LLJ as it becomes important in the skew-T analysis. So far, GFS skew-Ts really show this as the potential for areas of possible precip could occur. Though precip will likely occur from 00Z Wednesday to 09Z Wednesday. At 00Z Wednesday, moisture here is aloft though negative omega is spread out from 900mb to 500mb with highest at 9mb/s. This forcing ascent along with the LLJ bringing in continuous moisture implies that showers are likely to fall. Further support includes the LI staying between -1 and -2, an LCL ranging 900mb to 850mb between 06z Wednesday to 09Z Wednesday as winds turn southerly at the surface. It is also important to note the DCAPE is 403 at 09Z Wednesday thereby showing that winds at the surface are 30kts. It is important to note this because this helps us know how much moisture will continue to be supplied to this storm system leading to potential rain showers as Wednesday approaches.

By Wednesday, the 15ZWednesday GFS skew-T has continuous negative omega values from 900mb to over 500mb with the highest being 8mb/s. Moisture profiles only show a dry slot below 850mb thereby indicating the continuation of showers as LI stays between -3 to -4, LCL staying below 850mb between 15Z Wednesday to 09Z Thursday. The potential for hail will not be ruled out because of the amount of availability of forcing ascent between 15Z Wednesday to 09Z Thursday. Though the main event will be thunderstorms because of CAPE values ranging from 800 J/kg to 1000J/kg and rain throughout the day as all skew-Ts show moisture filling the gap of dry areas.

Transition into Thursday, the morning shows the only possible areas of a potential thunderstorm, but mostly rain. This is noticeable at 12Z Thursday as winds switch to west-northwesterly from 850mb to 500mb as CAPE is still above 1000J/kg, and negative omega at the from 950mb to 800mb with highest of 5mb/s. Though a significant dry slot appears over 700mb to 500mb as this indicates most of the low-pressure system has moved off into the east. From 15Z Thursday to 21Z Thursday, CAPE continues to decrease with moisture at the surface to 850mb over this time. So the potential for rain should not be completely ruled out as the LCL stays below 900mb and PW decreases from 1.05in to 1.04in.

Lastly, the potential for flooding can be seen with this slow-moving low-pressure system over Missouri. SREF plumes indicate that total rain amount could reach 1 inch by Thursday. GEFS shows total rain amount could accumulate to a little over 1.5 inches. The amount of rainfall may be around 1.25 inches because of the amount of surface heating received will be one of many factors that will assist in convection for the storm over the next couple days. It also depends on how slow this pressure system moves because it is not being completely influenced by a jet streak. Thus, the next forecast session should look at the potential for a chance of hail Wednesday evening into the night, flooding, and the position of the low to predict rain amount.

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