Friday, February 17, 2023

  

 Current Conditions at Sanborn Field



 

Friday Night: Mostly Clear. Low:30





Saturday: Cloudy. High:50





Saturday Night: Decreasing clouds, with scattered sprinkles. Low:36


 


Sunday: Increasing clouds. High:56

 



Sunday Night: Mostly cloudy. Low:  35
 

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Discussion: 


Above average temps should carry into the weekend, with a chance for drizzle Saturday night. Otherwise, a rather normal weather weekend seems ahead of us.


Thomas

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Forecasters: Thomas, Sausen, McGuire

Date Issued: 2/17/2023 4:30 PM CST

Technical Discussion:
 

    Conditions at the start of this forecast are stable with visible satellite imagery shows a clear sky over the CWA at the time of this forecast shift. Observed surface winds are out of the southwest as of Friday 21Z. The 12Z run of the GFS is used for this forecast due to its accurate temperature readings across the CWA as well as accurate positioning of frontal gradients across the Dakotas and Canada. This forecast will focus on the chance for light rain on Saturday night.

    300mb winds are zonal over the CWA until a shortwave passes from the west bringing in a small jet streak to the south with maximum winds of 135 knots on Sunday 03Z. Small amounts of upper-level divergence will accompany this shortwave as well, which could supply a small amount of lift. Another, larger jet streak then approaches from the west Sunday 18-21Z with winds of 180 knots at maximum.

    Winds at 500mb reflect the same zonal flow until a shortwave passes overhead on Saturday 21Z adding a southwesterly component. A wave of high vorticity values passes over from Saturday 21Z to Sunday 21Z. This is followed by another band of vorticity on Monday 06Z.

    700mb winds transition to a more zonal flow as the trough exits the CWA. They then shift to a more southerly component as the shortwave enters the CWA on Saturday 18Z. Relative humidity values approach 98% with trace amounts of upward vertical velocity providing a weak amount of lift on Sunday 03Z Another wave of moisture with similar amounts of vertical velocity will pass through on Monday 06-12Z.

    850mb winds are zonal from Friday 21Z to Saturday 18Z. They then switch to a southerly component. A small area of high RH passes from the southwest on Sunday 03Z. Small amounts of WAA are present until Saturday 21Z. Another, larger wave of WAA passes over from the west Sunday 06-15Z. Solenoids formed at the surface in combination with a southerly wind indicate small amounts of WAA Sunday 03-12Z.

    GFS model soundings show saturation in the upper levels on Sunday 06Z, but with a dry layer near the surface and nearly no upward lift, eliminating any chance for heavy rainfall or convection. Any precipitation that would reach the ground would be light. Surface high temperatures are trending slightly above the seasonal average for this area with highs breaking into the upper fifties compared to the average of 46 degrees Fahrenheit for Saturday and Sunday. This may be due to more southerly wind components brought on by shortwaves advecting warmer air into the region.


-Sausen





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