Wednesday, February 26, 2020

Wednesday Night - Mostly Clear. Low: 22-26 
Thursday- Increasing Clouds. Sprinkles possible in the afternoon. High: 42-46  

Thursday Night - Mostly Cloudy. Low: 26-30

Friday - Mostly Cloudy. High: 42-46

Saturday - Mostly Sunny. High: 56-60

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For tonight, expect clouds to clear. This will allow lows to drop into the mid-20s. On Thursday, winds will become southwesterly, helping mid-Missouri to warm up more than today. Maximum temperatures will likely reach the low to mid-40s. Clouds will be on the increase during the afternoon hours due to a passing disturbance, which could also squeeze out a few sprinkles. For Friday, expect temperatures to stay in the 40s, with westerly winds and mostly cloudy skies keeping us from getting much warmer. That warm-up will have to wait until Saturday, which -- with southwest winds and brilliant sunshine -- should reach the upper-50s.
Forecasters: Pauley, Vanderpool, Ritter
Issued:  5:00pm: February 26, 2020

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

The 18z NAM and 12z GFS showed remarkable agreement (through analysis of 500mb heights and winds) throughout the forecast period. With the WPC recommending a general model blend (and with the NAM progging Wednesday afternoon temperatures about 10 degrees warmer than observed values) we went with the 12z GFS throughout the period, as it had a better handle on surface temperatures.

21z WPC analysis indicated a surface low centered over West Virginia. This low was tilted west with height, as confirmed by 21z RAP analysis. The 500mb trough was just barely beginning to see a negative tilt, with its axis extending from northeastern Minnesota through central Illinois. Short-term prognostics from the RAP and GFS indicates that this trough will take on a steep negative tilt over the next 18 hours, which will serve to deepen the surface cyclone over the eastern CONUS.

For mid-Missouri, wrap-around moisture between 850 mb and 700 mb was responsible for cloudy skies, with relatively steep (7 - 7.5 C/km) low-level lapse rates helping to generate cumulus clouds and even a few snow showers. Lapse rates will become less steep throughout the evening, which -- along with drying in the aforementioned 850-700 mb layer -- will lead to clearing skies.

Tonight, clearing skies and light winds will help us to fall into the low to mid 20s. We decided to raise overnight lows a few degrees from the previous shift based upon SREF and HREF model spreads, which both forecast temperatures in the 22 - 27 degree range. Given that there is no snow on the ground, we believe that a range of 22-26 degrees is reasonable.

Thursday, surface winds will switch to the southwest. GFS soundings for 15z Thursday indicate veering in the low and mid levels of the atmosphere. That veering will create warm air advection, boosting surface temperatures into the mid-40s. Tomorrow afternoon, a small shortwave will push into the area. This disturbance will saturate the atmosphere between 850 and 300 mb, leading to increasing cloud cover. There is also the potential for sprinkles or light passing showers, as the saturation aloft is accompanied by decent vertical motion. However, any rain will have to fall through some pretty dry air near the surface, which will limit our overall chances for it.

Friday, another shortwave disturbance will pass over the area. However, it doesn't have much moisture to work with at the surface, so right now it looks like clouds will be the main impact. Future shifts will need to watch this, however, because any increase in moisture and lift could lead to more stray showers or sprinkles.

Saturday, a warmup begins in earnest as strong warm air advection combines with mostly sunny skies beneath a developing ridge. It currently looks like temperatures should hit the mid- to upper-50s, with warmer temperatures certainly not out of the realm of possibility. 

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