Current Conditions at Sanborn Field
Friday - Rain possible by the afternoon. High: 54-58.
We have another rainy end of the week in store for us in Central Missouri. Central Missouri is currently under a frost advisory through 8 AM Thursday morning. Thursday should remain a fairly pleasant day. However, clouds will begin to grow in the afternoon ahead of a low pressure system. As a result, rain should be expected beginning Friday afternoon and should remain in our area until Saturday evening. While not a lot of rain can be expected, be prepared for anywhere from 0.1 - 0.5”.
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Current WPC sfc analysis shows a relatively quiet pattern in mid-MO. A weak cold front stretched from roughly Springfield, MO to Paducah, KY to Detroit, MI. This was attached to a disorganized low centered in the upper Great Lakes region. Visible satellite indicated mainly clear conditions over much of Missouri, with high clouds beginning to stream off of a complex of showers and thunderstorms in Oklahoma.
In the near term, the upper-level perturbation responsible for sparking off the rain in Oklahoma will translate east. However, short-range hi-res models indicate that this will have little to no affect on our sensible weather as it does so. The aforementioned high clouds will likely continue to push their way into mid-MO, which may result in some increased cloudiness by late this evening or into the overnight hours. Nevertheless, our main focus of tonight will be on cooling temperatures and the potential for frost. Right now, the HRRR and the 12 UTC HREF look to keep the majority of clouds - even high clouds - mainly south of COU. Given mainly clear skies and modest CAA at the surface, as well as the presence of an already cool and dry airmass, lows overnight should tank into the middle 30s. Light surface winds on the order of just 4-8 kt and fairly high relative humidity will make for a patchy frost potential early Thursday morning. As a result, a frost advisory is in effect from 1 AM to 8 AM CDT Thursday.
For Thursday itself, look for a partly to mostly sunny start to translate into increasing afternoon cloud cover. A positively-tilted upper-level trough will start to dig its way into the eastern Rockies, favoring modest cyclogenesis on the lee side of the mountain range. However, the GFS and extended HRRR do not advertise this becoming a closed surface low; rather, it is likely to remain a rather disorganized system as it begins to affect mid-MO. The GFS/GEFS indicate fairly strong moisture advection in the mid levels of the atmosphere for Thursday night into Friday; however, the mean flow between 850-mb and 500-mb will be southwesterly. This likely indicates that there will be no significant plume of Gulf moisture for this system to work with, so it will be relying primarily on what spreads in from the Pacific. As a consequence, clouds will increase Thursday afternoon and become widespread Thursday night into Friday.
The main window of precipitation currently looks to exist from Friday evening through Saturday evening, though rain is likely to begin as early as early to mid afternoon on Friday. One interesting thing to note is that, according to the 18 UTC NAM, a layer of dry air may exist between 850-mb and 700-mb, thanks to strong easterly flow in that layer. The GFS is not as sold on this. If this dry layer does exist, it would mean a later start to surface precipitation, as the atmosphere aloft would need to saturate before rain starts to reach ground level. Regardless, it appears that rain will be falling by 00z Saturday.
Rain is likely to continue overnight Friday into Saturday, courtesy of ample moisture and decent lift aloft. The disorganized system, however, will begin to lose its punch by Saturday afternoon. This will result in a rapid loss of lift and thus a decrease in the intensity and scope of precipitation. The SREF means are sitting at ~0.6 inches of QPF throughout the duration of the event; the GEFS means are slightly below 0.5". Given the disorganized nature of the system and the potential for dry air intrusion in the mid-levels of the atmosphere on Friday, probability suggests that true QPF will probably fall between 0.1 and 0.5 inches, with most receiving 0.25-0.5".
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