Current Conditions at Sanborn Field
Thursday: Increasing cloudiness with spotty t-storms developing during the afternoon. High: 83
Thursday Night: Partly cloudy. Patchy fog possible by morning.
Low: 68
Friday: Mostly cloudy with scattered showers and thunderstorms possible (mainly during the late afternoon). High: 80
Friday Night: Considerable cloudiness with showers and thunderstorms likely (especially after midnight). Low: 66
Saturday: Periods of showers and thunderstorms. High: 78
Discussion:
Increasing clouds throughout today will lead to the chance for scattered showers and storms to develop, though the probability of rain decreases considerably into the overnight hours. An approaching trough from the Rockies will move toward our region throughout Friday into Saturday, with southerly winds increasing moisture content and increasing cloud cover even more. Temperatures will remain in the upper 70s to low 80s over this period, with chances of rain increasing with each successive day. Rain will be scattered at the beginning of this forecast period, becoming more organized and concise as we enter the weekend.
====================================================================
Forecasters: McDonald, VanUnnik, Aldrich
Date Issued: 09/30/21 9:30 AM CST
Technical discussion:
The 06Z GFS model run was used in the forecast today because it handled the
movement of the low-pressure system over the Rockies and the temperature pattern better than the NAM. GFS soundings were
used to evaluate moisture, instability, and temperatures as well as timing for
precipitation.
The 250-mb plots of heights, winds, and divergence show a long-wave ridge dominating the central United States at the start of the forecasting period that starts to move out of the area quickly over the next 24 hours. Divergence aloft continues to increase around the area as the low approaches by late Friday and into Saturday. With no indication of any jet streaks or stong wind speeds aloft, the general flow remains meridional flow with southerly winds until the area of low-pressure moves into our region by late on Saturday
.
Vorticity plotted against heights at 500-mb shows Missouri under the influence of an area of PVA starting late Friday and into the day on Saturday. This circulation of vorticity and area of low-pressure will strengthen over the next 24-36 hours bringing an increasing amount of cloud cover and chances for showers and thunderstorms - especially by late Friday and into the day on Saturday.
At 700-mb, moisture continues to move into the region ahead of the area of low-pressure moving in from the west. Omega and RH levels continue to increase throughout the day on Friday, into Friday night, and during the day on Saturday. This would indicate a good opportunity for periods of showers and thunderstorms throughout the forecast period.
The 850-mb plots of heights, winds, and temperatures show that the region will be in a favorable position to warm into the upper 70s and low 80s due to the placement of the high-pressure system off to our southeast, and the arrival of the area of low-pressure moving in from the Rockies. Winds from the south will advect moisture into the region from the Gulf of Mexico, allowing for considerable cloudiness and the increasing change for showers and thunderstorms from Friday night into the day on Saturday.
The GFS soundings show the atmosphere becoming more and more saturated throughout the rest of the forecast period. Instability parameters look relatively low (CAPE values reaching almost 800 J/kg and the LI at -3 by Saturday afternoon), so while there could be some convection, severe weather appears to be very low.
Future forecast shifts will need to monitor the potential for fog late tonight and into tomorrow, as well as the chances of convection ahead of the vorticity maximum approaching the region late Friday night and into the day on Saturday/
No comments:
Post a Comment