Current Conditions at Sanborn Field

Wednesday: Overcast. Rain beginning later. High: 62
 
 

Wednesday Night: Rain. Low: 32
 
 

Thursday: Freezing rain in the early morning. Sleet late morning. Snow by early afternoon. High: 24

 

Thursday Night: Snow ending. Clear. Low: 8

 

Friday: Sunny. High: 31

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Discussion:

 

Buckle up and prepare for this weather rollercoaster that will be making its way into mid-Missouri over the next few days. With a winter storm watch in effect until Thursday afternoon and a chance for thundershowers tonight, we are in for a wild ride. The warm and mild start to the week will quickly become cold and harsh. Today will start out quite spring like with temperatures and rain showers starting late this afternoon. Rain will persist into the overnight hours before beginning a transition into a winter precipitation in the early morning hours on Thursday. While it looks unlikely, a rumble of thunder or two is possible tonight. Rain totals are expected to be around 1.5 inches. After midnight, a strong cold front will sweep through mid-Missouri causing us to hit our high temperature just after midnight and drop our temperatures throughout the day. As temperatures drop in the early hours on Thursday, we will see a transition to freezing rain and then to sleet by mid-morning. This has the potential to cause hazardous travel for the morning commute on Thursday. MoDOT will not be pretreating the roads since the rain would just wash it away. After the transition, temperatures will be too cold for road treatments to be effective. Be sure to allow extra time for travel. Sleet will transition into snow mid Thursday afternoon and all precipitation will stop late afternoon or early evening Thursday. Total snow accumulations are expected to be between 2-4 inches. A continuous northerly wind will leave Friday morning with bitterly cold temperatures.


-- Kobielusz

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Forecasters: Kobielusz, Macko, Bongard

Date Issued: 2/16/2022 10:00AM CST

Technical Discussion: 

 
The deterministic model chosen for this complicated forecast is the 06Z run of the GFS20. The GFS verified the location of the low-pressure center in central Kansas and the cold front draping across portions of the Central Plains and Upper Midwest at 09Z and 12Z this morning. The GFS also provided highly accurate temperatures throughout the morning hours on Wednesday, something that the NAM failed to do. In addition to the GFS, NBM, and forecast soundings were used to help nail down the specifics of this forecast.

 

Wednesday morning begins with a jet streak in excess of 110 knots encompassing the state of Missouri. Upper-level divergence is not particularly notable until early Wednesday evening where it becomes more widespread across the mid-Mississippi Valley. The previously mentioned jet streak is set to strengthen throughout the evening and overnight hours on Wednesday, with wind speeds peaking just under 150 knots. It is also during the late overnight hours in which a well-defined area of upper-level divergence will transverse the Southern Plains and move into Missouri. Both widespread and in great magnitude, this region of divergence will persist into the morning hours on Thursday. By early afternoon on Thursday, divergence becomes significantly less prevalent and the jet streak over Missouri weakens. By Friday, the jet streak moves eastward, and mid-Missouri will fall under the influence of a much weaker portion of the jetstream. 

Vorticity plots for Wednesday are rather unremarkable for the mid-Missouri region. However, by Thursday morning, vorticity across the Central Plains and the mid-Mississippi Valley is extremely impressive, another important ingredient for the anticipated precipitation on Thursday. Vorticity will push further south Friday morning, no longer impacting mid-Missouri.

The 750-mb level lacks moisture at the start of the forecast period. Just as variables at all other levels thus far have done, moisture will dramatically increase over the Central Plains and mid-Mississippi Valley during the early morning hours on Thursday. Positive vertical velocity also becomes increasingly enhanced around this time but will quickly move out of the region later on Thursday. Moisture is expected to remain into the late evening hours on Thursday but will proceed to dry out just after midnight.

A considerable low-level jet with southerly winds is stationed over Missouri early Wednesday. This will provide warm, moist air from the Gulf of Mexico, further encouraging rainfall later in the day on Wednesday. The LLJ should begin to move southeastward during the early morning hours on Thursday and northerly flow will prevail. The exact timing of when this LLJ moves out of mid-Missouri will affect precipitation changeovers and, consequently, snow and ice accumulations. This is a likely reason for the widespread model disagreement when it comes to snowfall totals.

GFS and SREF soundings suggested that the warm layer at 850-mb and higher would persist until early Thursday afternoon. However, temperatures and dewpoints near the surface are expected to dip below freezing between 10Z and 11Z Thursday morning. Temperatures will continue to drop both at the surface and between 850-mb and 700-mb heading into the afternoon. The "warm nose" should fall below freezing by later Thursday afternoon. Thus, the changeover pattern is forecasted to be as follows: (1) rain to freezing rain between 10Z and 11Z, (2) freezing rain to sleet around 14Z, and then (3) sleet to snow between 18Z and 20Z.

 

The NBM 07Z run was used as a guiding tool in determining precipitation totals. Though not as significant, uncertainty was still evident in the NBM and its outputs were altered by the forecasters accordingly. At this time, total rainfall accumulations are expected to between 1" and 1.5". Ice accumulations are anticipated to be 0.1", while snow accumulations are planned to be between 2" and 4". Future forecasters should be aware that these totals could potentially change with updated model guidance about precipitation transition times.

 

- Macko