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Heading into the afternoon, we are expected to start seeing cloud cover take over ahead of approaching storms. Storms will reach Columbia an hour or so before midnight. The main potential threat of these storms would be severe winds, however severe winds are unlikely. Storm Prediction Center places Columbia in a Marginal risk for severe winds. These storms will be associated with a cold front passing through Columbia. Friday will see humidity drop a good amount, along with temperature, leading to a rather nice day outside. Saturday will see our winds shift from being out of the north to being out of the south, bringing humidity back up, along with temperatures. Sunday will also see temperatures continue to rise to above seasonal average.
Issued: 1:00 p.m. ; September 12, 2019
Technical Discussion (The nerdy stuff we are discussing in class!)
WPC Guidance indicates good resolution across every model except for the CMC of the draping cold front, and thus the GFS will be the primary model of choice, with supplementary use of the HRRR. This evening will see cloud cover start to take over Columbia ahead of the approaching cold front. The 12Z GFS and 16Z HRRR seem to have good agreement on the storms reaching Columbia around 11pm tonight. The 16Z HRRR seems to have weakened the storms a fair amount right before they hit Columbia, with the line of storms breaking into two segments; the much stronger line passing through Wisconsin, and a fairly weak and angled line crossing Missouri. This breakage is indicated as happening right over Columbia. Previous HRRR runs indicate that there will be some sort of breaking of the line around 11pm, however more recent runs keep breaking the line into 2 segments farther south. The 12Z GFS does not only break the line into 2 very near Columbia, but kills off the southern segment of the storms very soon after the breakage. The agreement among models of a fairly significant weakening very near or over Columbia is something to take note of. If this line does end up breaking into 2 directly over Columbia, there is a decent chance that Columbia may not even see rain. SPC has placed us in the marginal risk for severe winds, which seems to be a fair assessment. 12Z GFS soundings show about 700 J/kg of DCAPE, which has the potential for severe downdrafts and outflows, but only just. This environment is very marginal, and the storm is expected to behave as such. Friday will see a surface high setup just off to our west, which will setup CAA into the area. This CAA will keep temperatures down during the day Friday, along with keeping humidity fairly low, leading to a seasonably average day in September. Friday night will also see this CAA, and thus keep our low temperature on Friday night in a normal September range. Late Friday night into early Saturday morning will see this surface high track directly over Columbia, and begin fairly strong WAA during the day Saturday. Not only will temperature increase, but also humidity. WAA is expected to stay in the forecast through the rest of the period. As the high to our east moves out, a surface low will be moving east out of the Rockies and into Kansas on Sunday morning. Thus, a decently strong warming trend has been set in the forecast throughout the week. Temperatures Sunday will begin to rise well above seasonal averages, along with high dew points, leading to muggy conditions in September yet again.