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As we end our Monday, temperatures are expected to cool to the mid-50s with clouds entering overnight. Tuesday will be the warmest day of the period, with afternoon highs approaching 80 degrees and clouds will continue to stick around. Tuesday night will be quite mild, with overnight lows around 60 degrees as clouds dominate the sky. Wednesday will be slightly cooler than Tuesday with afternoon highs in the mid- to upper-70s with overnight showers to occur during the night. Thursday will be cloudy with temperatures similar to Monday's high.
Forecasters: Danaher, Browne and Hirsch
Issued: 5:00 p.m., 15 April 2019
Technical Discussion (The nerdy stuff we are discussing in class!)
The WPC suggested a Non-NAM blend because the NAM amplified the trough digging more southwest on the CONUS. This would lead to slower progression than compared to the rest of the models and it also means the ridge on the east would be less amplified. Overall, the NAM would be an outlier later in the week for a forecast tool which is why the GFS will be the chosen model for this forecast.
Throughout this forecast period the atmosphere will be more active during the middle of the week. The affects of pressure are slowly decreasing due to the low-pressure system over southern South Dakota. A second low-pressure system is south-west over the Colorado-Kansas border and will become important later on Wednesday. As we transition tonight into Tuesday Morning winds will continue westerly flow at 250mb because of the jet streak northeast of Columbia moving east across the CONUS. Columbia is on the warm sector of the low-pressure system over South Dakota and is the reason why maximum temperatures will be almost in the 80's.
By Tuesday night, as the jet streak northeast of Columbia moves into the Great Lakes another jet southwest of Columbia will follow behind. A backing wind profile (westerly to southwesterly) will occur over our region with CAA following. The low pressure system over South Dakota has moved into the Great Lakes. GFS skew-Ts shows that moisture will enter above 250mb as this will support the low-pressure sytem over the Great Lakes. Meanwhile the low-pressure system over Colorado-Kansas border has started to deepen as it moves into Texas-Oklahoma border. The jet streak southwest of Columbia will have an influence on this second low pressure will go as we enter into Wednesday and Thursday.
As Wednesday approaches, the jet streak that is southwest of Missouri will sweep over Texas as another jet streak will sweep over Missouri. the second low pressure system will have a cold front that connects to the low over the Great Lakes. Vorticity values will increase as Wednesday progresses and according to GFS skew-Ts Columbia will reach about 20-24 microb/s at 03Z Thursday. CAPE values will peak around 853J/kg and omega values will range from 0 to -1.73x10^-2 along 975mb to 500mb at 03z Thursday. So it will rain, but the possibility of lightning is small because I believe most of the severity will occur in Southern Missouri since this is the core of divergence aloft continues to stay above 8. Rain should reach the ground between 03Z to 06Z Thursday and is expected to accumulate a little over half an inch; however, this is subject to change in later forecast periods.
By Thursday, the jet streak over Missouri will create a core of over 65kts at 250mb as Columbia will be on the ridge. GFS skew-Ts show that at 12z Thursday, omega values become positive as they range from 7.37x10^-4 to 5.53x10^-3 along 925mb to 625mb. This means that forcing for