Current Conditions at Sanborn Field
Freeze Warning in effect from April 21 01:00AM CDT until April 22 09:00AM CDT
Wednesday Night- Decreasing cloud cover. A freeze is likely. Low: 28-32
Thursday - Partly sunny. High: 54-58
Thursday Night - Cloudy. Rain is possible late. Low: 42-46
Friday - Cloudy. Rain possible throughout the day. Thunderstorms possible late. High: 54-58
Another freeze warning has been issued for the forecast area for tonight through tomorrow
morning at 9 AM. Low temperatures are expected to yet again fall below freezing tonight as
minimal clouds allow for us to cool down quickly. Tomorrow, we'll be under the influence of
high pressure which will allow for sunny skies to be the story throughout most of the day.
Clouds will begin to build back in late Thursday ahead of lower pressure that will be bringing
our next rain chances to the area. Rain showers may start late Thursday night and are expected
to continue throughout the day Friday. We could see some thunderstorms mixing in for Friday
evening as well.
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This forecast was assembled using the 06Z GFS and subsequent soundings from this model. Both the GFS and the NAM had a good handle on where the low pressure system and cold fronts impacted the area yesterday are now located. Forecasters chose the GFS over the NAM because the trough located to our northwest was accurately portrayed.The main forecast focus for today will be the overnight freezing potential followed by rain to close out the week.
The 250-mb level shows troughing over the forecast area this morning. This trough is helping to produce the unseasonably cold weather that we're seeing today. As the forecast period continues on, a ridge will push into the area by 21Z Thursday. This ridge will help to keep sunshine in the area as higher pressure settles in. Another trough located to the west of the area at 21Z Friday will bring in more cloud cover to the area.
The 500-mb outputs show minimal vorticity in the area throughout Wednesday and Thursday. Vorticity will enter the area Friday at 06Z as a trough approaches. This vorticity will help to kickstart our rain chances for Friday.
At the 700-mb, moisture is present, but not in a high capacity. This suggests that few clouds may stick around. Around 03Z this evening, that moisture exits the area, and with it, the cloud cover will exit as well. The lack of clouds will allow for radiative cooling overnight, dropping temperatures below freezing once more. Moisture will not be present Thursday, but at 00Z Friday, that moisture will re-enter the area. Saturation at this level will allow for cloud development along with increasing rain chances throughout the day Friday.
850-mb level output suggests CAA coming on the backend of the low pressure and cold front that moved through yesterday. This is contributing to the cooler start to our Wednesday. Luckily, winds will shift to become southerly by 18Z Thursday. This will aid in warmer temperatures for Thursday, but it will also begin moisture transport from the Gulf of Mexico. By 09Z Friday, winds will increase to 35kt out of the southwest.
At the surface, CAA is still present until Thursday at 18Z when winds shift to become southerly. This CAA advection will give us a chilly Wednesday and Wednesday night. Thursday will be pleasant and calm with an area of high pressure located directly over us. By Friday at 00Z, that high pressure moves out. Moisture transport at 18Z from southerly winds help to feed rain chances on Friday.
Soundings suggest that, even though moisture is present on Wednesday, the presence of a dry layer from the surface to 750-mb will prevent any rainfall from reaching the ground. Thursday night, saturation makes its way back into the atmosphere around 03Z Friday. This saturation will be present throughout Friday. We can expect rain to impact the area from the time we wake up through the end of the work week. Something to note is the presence of little CAPE. With low CAPE values, we don't expect more than the odd rumble thunder for Friday.
Future forecaster should watch the trough as it pushes toward mid-Missouri.
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