Current Conditions at Sanborn Field
Friday - Partly sunny. High: 46-50
Friday Night - Partly Cloudy. Low: 36-40
Saturday - Partly cloudy becoming overcast. High: 58-62
Saturday Night - Rain Low:40-44
Sunday- Windy and mostly sunny. High: 50-54
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Discussion:
A chilly but partly sunny day is in store for Mizzou's campus as the work week comes to a close. Clouds will increase later tonight and jackets will be necessary for anyone venturing out as the area will experience a typical late fall evening. Tomorrow, rain chances are better over southern Missouri than here in mid-Missouri during the morning hours though an isolated shower making it north of the Lake of the Ozarks cannot be ruled out. Precipitation chances are better in Columbia Saturday evening when the region will experience yet another cold front passage. Rain will be brief as the front scoots through Columbia quickly and the area will dry out for a sunny but slightly colder Sunday.
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Forecaster: McGuire, Bongard
Issued: 10 AM CST 13 November 2020
Technical Discussion (The nerdy stuff we are discussing in class)
Friday gets the weekend off to a chilly start as a cold front passed through the Columbia between 21Z and 22Z Thursday afternoon.This forecast was assembled using the 06Z GFS model output including model soundings and time-height cross sections. SREF and GEFS are referred to for consensus.
Observing the current 250-mb heights and wind speed(kts) most of the CONUS is in zonal flow with a jet streak core over the plains. At 12Z Mid-Missouri is placed in the left exit region of this jet streak. Taking a cross section showing Omega, that crosses through Columbia with endpoints of Ottumwa, IA and Stuttgart, AR. Over Columbia at 12Z there is weak divergence aloft and weak convergence in the low levels at this time. The divergence above the region continues to increase until reaching its maximum around 00Z Saturday as mid-Missouri transitions into the right entrance region of the core, but still not a great amount of convergence at the surface. At 09z Saturday, convergence at the surface with weaker divergence aloft leads to development of rain showers in southern Missouri, but by 12Z, a significant area of divergence from the surface to about 400-mb looks to put a damper on things before reaching Columbia. As the zonal flow moves eastward, a trough moves into the region and will influence the rest of the forecast through Sunday afternoon. We will find ourselves just west of the trough axis at that time.
Looking at the 500-mb heights and vorticity, our main concern will be during the morning hours Saturday and again Saturday evening into the night. Saturday morning between 09Z and 12Z vorticity advects into the region, but as said in the 250-mb chart analysis due to divergence, Columbia should see limited effects if any in terms of precipitation development. Sunday at 00Z, significant amounts of vorticity advect into mid-Missouri exiting by 12Z.
Friday will remain dry with some clouds moving into the area late in the evening as rain develops to the southwest. The atmosphere over Columbia is going to be too dry for this rain to travel northward. Saturday night into Sunday morning as a cold front begins to make its way through the region an LLJ exceeding 60 kts is visible on the 850-mb wind speed chart. This helps provide moisture from the Gulf of Mexico as a southerly to southwesterly flow is present at the 850-mb level. With this said, the significant moisture transport does not take place until after the front passes through and will increase precipitation amounts to our east, whereas we should expect up to 0.15 inches of rain.
Fridays temperatures stay chilly, but WAA provides a nice warm up into the 60s Saturday before the cold front. Post FROPA, there will be significant CAA dropping temperatures into the low 40s.
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