Tuesday Night- Cloudy. Rain after midnight. Low: 44-48
Wednesday- AM Rain/PM Clouds. High: 64-68
Wednesday Night- Cloudy, Rain. Low: 58-62
Thursday- Cloudy, Rain and Potential Thunderstorms. High: 68-72
Friday- AM Clouds/PM Sun, Colder. High: 42-46
Discussion:
The overcast skies that started out today will continue overnight. Along with the cloud cover, the potential for rain and warmer temperatures ramp up for the middle of the week. This is due to a high pressure over the southeast bringing winds from the south bringing in those warmer temperatures and moisture needed for this midweek rain. A cold front will start to make its way into the area late Thursday night. This cold front will bring along with it the potential for some thunderstorms. Once the cold front passes early Friday morning, skies will begin to clear, and temperatures will be much colder than earlier in the week.
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Forecasters: Gallahan, Munley
Issued: 5:00pm: March 17, 2020
Technical Discussion (The nerdy stuff we are discussing in class)
WPC recommends a blend of 12z GFS and 00z ECMWF. Overall, 12z GFS was used for this forecast. SREF Plumes were used for rainfall totals.
The main topic of concern for this forecast is the warm up in the middle of the week, the potential for midweek rainfall, how much rain will fall and lastly the potential for thunderstorm development Thursday night.
Winds at the 250mb level indicate a zonal flow that is transitioning into more of a meridional flow. This is due to two anticyclones; one over the state of Nevada, and the other one over the southeast CONUS. The one of more concern is the one over the southeast. The reason for this is due to Columbia’s location being on the northwest side, the winds on the backside are coming from the south driving potential moisture from the gulf. There is also a lack of atmospheric circulation at the 500mb level until tomorrow morning when there is a shortwave that ejects out of the longwave located over the desert southwest and makes its way into Missouri late tomorrow morning into early tomorrow afternoon. This ejecting shortwave will increase the potential for rainfall overnight tonight into early tomorrow morning. This is due to this shortwave increasing 700mb RH values to rear 100% and UVM values to between 18-20ubar/s. This shortwave will be short-lived as the rain potential will decrease heading into mid-morning. Late morning/early afternoon however, the rain potential looks to rebound The key factor to the rain potential rebound is the 700mb RH and UVM. Currently, the RH values look relatively low along with the UVM remaining low overnight. Late tomorrow morning, those two values will begin to increase with the RH increasing to near 100% and the UVM reaching values of 15ubar/s. 850mb winds will also play a role. There doesn’t look to be much in the way of low-level wind support until late tomorrow morning as well. This low-level support along with the 700mb RH and UVM values increasing indicates the start of the rain to be late tomorrow morning. This rain looks to last all the way into late Thursday evening. This is when a potential for thunderstorm development comes into the picture. This is because there will be a cold frontal passage late Thursday night into Friday morning which will drive the CAPE values up to 1200 J/kg giving us the lift needed for the aforementioned thunderstorm development. When all said and done, total rainfall looks to be on the lines of 0.75 to 1in.
Temperatures will also be affected due to the anticyclonic flow over the southeast CONUS driving warm southerly air into the area for tomorrow all the way into Thursday afternoon. Heading into late Thursday night, there will be a wind shift which will cause a backing wind profile to develop causing high temperatures from Thursday into Friday to drop nearly 30 degrees. Along with the colder temperatures, there will be clearing skies post frontal passage.
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