Monday, September 9, 2019

Current Conditions at Sanborn Field

Monday Night - Mostly Clear, with isolated showers before sundown.         Low: 70-74
Tuesday - Partly Sunny, with a chance for showers in the evening.           High: 89-93
Tuesday Night - Becoming cloudy. Breezy. Low: 70-74
Wednesday - Partly cloudy, clearing in the afternoon. High: 89-93
 Thursday - Clouds building in.  High: 86-90

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Showers may build in later this afternoon, with a possible rumble of thunder.  These storms will fade as the sun goes down.  Lows for tonight will stay rather warm, in the lower 70s.  The rest of the week will also see rather warm temperatures, with values in the lower 90s.  The first half of the forecast period will see cloud cover, with potential for pop-up storms and showers.  During the day on Wednesday, cloud cover will decrease, as will potential for pop-up storms.  Thursday will see the return of clouds, keeping temperatures slightly lower than the previous few days. 
Forecasters: Heaven, Hatch
Issued:  5:00 p.m. ; September 9, 2019

Technical Discussion (The nerdy stuff we are discussing in class!)
WPC Guidance indicates the NAM having poor resolution of the general pattern over the CONUS, and thus the preferred model is the GFS, and supplementary usage of the HRRR.  This morning saw the passage of a warm front, increasing temperatures and humidity across the area.  Temperatures are above average,  with temperatures in the low to mid 90s, along with a dew point of 71.  Current data from Sanborn indicates Heat Index Values approaching 100 degrees, however temperatures will begin falling in the next few hours.  Temperatures throughout the week will remain high, as we will remain in the warm sector of 2 different lows.  Staying within these areas will keep our winds out of the south, keeping temperatures and dew points high.  However, temperatures will simply remain high instead of increasing.  12Z GFS indicates very few, if any, solenoids forming, and thus keeping WAA to a minimum.  The first surface low will move off to our northeast during the day Tuesday.  This surface low is currently located in Montana, and is headed east.  The cold front attached to this surface low will not pass over us, as it is wound fairly tightly to the low, and will remain to our north. 

The 18Z HRRR is indicating possibility for pulse storms near Columbia tonight, and thus a chance for isolated storms has been put in the forecast.  Once the sun goes down, this convection will cease, and we will remain mostly clear through the night, with relatively high lows in the lower 70s. 

On Tuesday, the cold front to our north will modify as it interacts with a surface low based in northern Wyoming, making the front become a stationary front across northern Iowa.  Tuesday again sees the potential for pulse storms, with the HRRR wanting more overall cells than Monday afternoon.  These storms will also be more widespread than Monday.  Convection will end as the sun goes down.  

Wednesday will be quiet, with no precipitation expected.  Clouds will clear up as the day goes on.  As the surface low  in northern Wyoming begins to move east on Wednesday, it will modify the stationary front into a warm front, and keep us in the warm sector.  The low will also start to close itself off as it comes down the mountains.  Our winds will remain out of the south.

During the day Thursday, clouds will begin to build as the cold front approaches.  12Z GFS guidance indicates that on late Thursday night, the Columbia area may see a potential for severe weather associated with the cold front.  With current guidance, a  night-time linear system with potential for damaging winds; however, newer guidance is required before assuming this is a severe threat. This system will have enough lift and moisture at the surface, with a good amount of divergence at the 250mb level.  The jet will also be in an excellent spot for this system.  Lapse rates, however, are rather low, at 6.5C/km.  Dynamically this system is adequate, however thermodynamically it is lacking.  As new guidance comes out, this situation will need to be monitored closely. 

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