Wednesday, April 7, 2021


Current Conditions at Sanborn Field

Thunderstorms in the morning and early afternoon, a few of which may be strong to severe. High: 66-70


Wednesday Night-
Rain moves out, but cloudy conditions remain. Low: 46-50

 Mostly cloudy. Spotty rain showers. High: 54-58


Thursday Night-
Spot shower will wrap up by morning. Low: 44-48

Friday -
 Mostly sunny. High: 70-74

 Thanks to for the icons!


Waking up this morning, we saw and heard the first round of thunderstorms for the day move through. While they produced some impressive lightning and small hail, overall, our main focus will be on the second round of storms expected to move through this afternoon. The low pressure system that is bringing on these storms is also going to usher in colder air behind it, so temperatures can be expected to fall throughout the rest of today. After the second round of storms moves through between 3-6pm, light rain showers will linger through the night and into tomorrow. The afternoon storms have the potential to produce small hail and gusty winds that could cause some damage. Thursday will be cooler courtesy of northerly winds, but we'll rebound quite nicely as we head toward the weekend.


Forecaster: Bongard, Baker, Est
Issued: 10:00 AM CST 07 April 2021
Technical Discussion (The nerdy stuff we are discussing in class):

This forecast was assembled using the 06Z run of the GFS as this model most accurately represented the two low pressure systems present at the surface level at the time of the forecast. Soundings from the GFS were also used in determining the severity of the afternoon storms. The main focus for this forecast period will the afternoon storms for today.

At the 250-mb level, a low pressure system located over the border of Kansas and Colorado is causing our upper level winds to be southwesterly. As this low tracks easterly, it can be expected to enter Missouri by 12Z Thursday. This low pressure system will leave the area by 00Z Friday morning. As this low pressure system pushes toward, over, and away from the area, winds will shift to become westerly, then southwesterly. There is no significant jet max present at this level during the forecast period.

500-mb plots show this low pressure system over the Panhandles region of the CONUS with a significant area of vorticity associated with this low pressure system. This vorticity will be located over the forecast area by 00Z Thursday.

At the 700-mb level, southerly winds at 21Z on Wednesday help to usher in moisture that will aid in thunderstorm development for the afternoon. As the low pressure system pushes through the forecast area, winds will shift to become northwesterly by 06Z Friday, ultimately cutting off this moisture transport. That will aid in drier conditions to close out the week. 

The 850-mb level, winds are southwesterly at 30 kts which is bringing moisture and warmth from the Gulf of Mexico. This winds will shift slightly to become southwesterly at 21Z Wednesday. At this time, that warmth and moisture transport from the Gulf will also help to aid in thunderstorm development for the afternoon hours. By 09Z Thursday, the winds will become westerly, cutting off the warmer air transport from the south. There is also no significant jet max at this level. 

At the surface, moisture is present in abundance. Southerly winds are bringing in that moisture, but as the low pressure system pushes toward the forecast area, a cold front will also approach. This surface cold front can be expected to pass through the area at 18Z on Wednesday. Cooler air will impact the area until 00Z Friday when winds shift to become southwesterly. This wind shift for Friday will help temperatures to climb back toward the 70s once more. 


All guidance suggests that the atmosphere is primed for thunderstorms to impact the area around 21Z today. With moisture and warmth transport from the south plus upward motion and CAPE values near 1000 J/kg, storms are likely for this time. Negative Omega values suggest that hail formation is possible, but our main concern will be with stronger winds as the line of storms pushes through. Limited shear gives peace of mind when it comes to tornadic development for this afternoon. Cloud cover can be expected to hold steady, which will block any fuel from the sun for this second round of storms. The SPC has placed us in a slight risk for the day with the primary concern being strong winds. 


Future forecasters should watch for any mesoscale discussions that may be published, and they should monitor updated guidance for any changes from the 06Z run.

No comments:

Post a Comment