Friday Night: Partly Cloudy. Low: 36
Saturday: Overcast. High: 49
Saturday Night: Clear. Low: 32
Sunday: Sunny. High: 53
Sunday Night: Mostly clear. Low: 36
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Discussion:
Generally calm and modest weather looks to prevail this weekend, although things look rather cold. High's around 50 and lows in the mid to lower 30's means frost potential, so be sure to bring those freshly potted plants indoors or cover them. Otherwise, largely sunny skies and gentle winds throughout the forecast period.
-Thomas
Forecasters: Thomas, Sausen, McGuire
Date Issued: 4/21/2023 4:20PM CDT
Observations over Missouri show clear, windy conditions. METAR station model plots show few to no clouds, and westerly winds at 15-25 knots. Visible satellite imagery shows Central Missouri in a dry slot with a wave building over northern Arkansas. The GFS is trending colder while the NAM is trending warmer. The GFS, however, has less deviation from the observe temperatures. It also fits this post-frontal weather situation better as a spectral model, so the GFS is the model used for this forecast. The primary focus of this forecast discussion is the possibility frost to form Saturday night.
At 250mb, the CWA lies to the north of the polar jet, leaving the area in a colder airmass throughout the forecast period. Upper-level winds are meridional in association with a longwave trough passing overhead through 15Z Saturday. Winds then return to a zonal, westerly flow with a jet streak positioned over Southern Missouri.
High vorticity remains in the CWA until Sunday 18Z in association with a low-pressure tracking to the northeast. Winds are in a zonal flow at about 40-60 knots throughout the forecast period.
750Mb winds are out of the west. The cyconic flow over Minnesota encourages stronger winds, capping at approximately 55 knots over the CWA until 00Z Sunday. RH values lie below 70% through most of the forecast period with the exception of Saturday 03-06Z where RH values max out at approximately 85% giving the possibility partly cloudy conditions Friday night.
850mb winds exhibit a westerly flow and veer to the north as time passes. Wind speeds are slower at this level at 20-30 knots throughout the forecast period. CAA is present consistently until Sunday 06Z. A small cyclonic flow builds into Southern Missouri from the west Sunday 18Z. A significant amount of low-level moisture advects in from the north Saturday 12Z through Sunday 06Z which may provide the moisture necessary for frost at the surface. The CWA dries out at this level through the rest of the forecast period.
Surface CAA occurs from Saturday 06Z through Sunday 06Z. Winds switch between westerly and northwesterly components throughout the forecast period. They pick up intensity Saturday afternoon with speeds approaching 15 knots. Surface temperatures approach 30 degrees F Sunday 09Z, giving temperatures cold enough for frost to form.
12Z GFS soundings show a thin layer of moisture present slightly above 850mb Saturday 15Z to Sunday 00Z, giving the possibility for cloud cover throughout the day Saturday. Surface temperatures fall below freezing Saturday night with weak surface winds. Surface temperature and dewpoints approach within 4 degrees of each other Sunday 12Z, giving a significant chance of frost occurring Saturday night into early Sunday morning.
NBM output shows a low of 33 degrees F on Saturday night in conjunction with surface RH values of 72%. The spread on the temperature box-and-whisker plot is tight, giving a small variability in temperatures through the forecast period. Cloud cover is low on Saturday night as well.
-Sausen
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