Tuesday, April 30, 2019

Tonight - Strong to severe thunderstorms. Low: 60-64.

Wednesday - Morning showers and thunderstorms, afternoon clouds. High: 72-76.


Wednesday Night - Showers and thunderstorms possible. Low: 60-64.

Thursday - Scattered showers and thunderstorms, afternoon clouds. High: 64-68.

Friday - Partly sunny, showers possible in afternoon. High: 64-68.  

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Temperatures remained fairly steady throughout the day today as the area saw thunderstorms during the late morning hours and stayed on the northern side of a stationary boundary and underneath cloud cover for the day.   There is possibility of strong to severe thunderstorms tonight as a low pressure system begins to meander its way through the area tracking southwest to northeast.   Primary concerns for the storms Tuesday night are large hail, damaging winds, flash flooding, and a possibility of a weak tornado can't be ruled out.  The rain and storm possibilities continues for the forecast area off and on during the day Wednesday, The low pressure system causing all this rain and activity will pass through the area just to our south along a stationary boundary line during the mid morning hours Wednesday.  Scattered showers do persist through Wednesday and Wednesday night, and Thursday afternoon.  During the day Friday that persistent stationary boundary does finally begin to make its much needed exit as a low pressure system from the Rockies sweeps through taking stationary front with it off to our east. High pressure fills in Thursday night into Friday.
Forecasters: Azzara, Munley and Hirsch
Issued: 6:00 p.m., 30 April 2019

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

This week will feature a very active pattern of weather with our main focus this forecast period being on the possible severe thunderstorms that will effect mid-Missouri this afternoon continuing on into tonight.

The big "if" for today was if we were going to see any sun after the round of rain that came through this morning. The answer to that question is yes! The sun was out in Columbia around 19Z and that helps fire up more convection leading to greater confidence of seeing strong to severe storms this evening.

Timing wise, the rain looks to push in from the west ahead of any storms and that should arrive within the next hour or two but the thunderstorms that are of concern will be effecting the viewing area from 23Z-03Z this evening. Reasons for placing the thunderstorms here at this time would be the use of varying indices. Totals totals index is sticking in the upper 40's which promotes thunderstorm development. Using the K-index from around 00Z-04Z has potential for heavy downpours which will lead to flash flooding, which the National Weather Service has placed a watch for until Thursday. The severe threat comes into play around 23Z when severeity the SWEAT index picks up to 369 (meaning severe t-storms potential). The Bulk Richardson Shear at that time will be 99 which is in the index of possible tornadic supercells. While our CAPE and Lifted Index values are not too impressive, the atmosphere will still be moderately unstable which is enough for severe storm possibilities. This system has a great amount of lift to it which rises another concern which will be hail. There is enough updraft for medium sized hail. Strong linear winds are a threat as well, looking at hodographs between 23Z and 02Z the winds are relatively straight-line, rotation is not a huge factor in the winds, causing confidence to skew towards stronger linear winds. Looking at 500mb vorticity, the best circulation over mid-Missouri will be around 02Z however, the circulation will not very strong, also aiding in the higher confidence in straighter winds. There is very low confidence for a tornado to spawn from this system within our forecasting area but via the SWEAT index, there is a marginal threat of a potential tornado after 02Z however, at this point in the evening, there will be extreme shear with BRNS being in the 200's which will tear apart any organized thunderstorms that are present at that time, leaving just heavy rain to follow.

This precipitation is in front a cold front but that cold front will turn into a stationary front that will stick right over Columbia which will drop rain through Wednesday and into Wednesday night. This could have a few scattered thunderstorms associated with it but severity is not of concern because that atmosphere will not be able to rebound enough from the storms from today to convect enough every to make severe storms tomorrow.

Thursday rain will became more scattered and shower like and dissipate into the mid-afternoon hours as the stationary front starts to push off to the east. Clearing is expected into the late afternoon and evening hours but storms could return by late Thursday night and into Friday. Chances for more thunderstorms continue through Friday but confidence on those storms are fairly low but have been increasing over the last few days.

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