Tuesday, April 30, 2019



Tonight - Strong to severe thunderstorms. Low: 60-64.



Wednesday - Morning showers and thunderstorms, afternoon clouds. High: 72-76.

 

Wednesday Night - Showers and thunderstorms possible. Low: 60-64.
 

Thursday - Scattered showers and thunderstorms, afternoon clouds. High: 64-68.



 
Friday - Partly sunny, showers possible in afternoon. High: 64-68.  



Thanks to IconArchive.com for the icons!




Discussion:

Temperatures remained fairly steady throughout the day today as the area saw thunderstorms during the late morning hours and stayed on the northern side of a stationary boundary and underneath cloud cover for the day.   There is possibility of strong to severe thunderstorms tonight as a low pressure system begins to meander its way through the area tracking southwest to northeast.   Primary concerns for the storms Tuesday night are large hail, damaging winds, flash flooding, and a possibility of a weak tornado can't be ruled out.  The rain and storm possibilities continues for the forecast area off and on during the day Wednesday, The low pressure system causing all this rain and activity will pass through the area just to our south along a stationary boundary line during the mid morning hours Wednesday.  Scattered showers do persist through Wednesday and Wednesday night, and Thursday afternoon.  During the day Friday that persistent stationary boundary does finally begin to make its much needed exit as a low pressure system from the Rockies sweeps through taking stationary front with it off to our east. High pressure fills in Thursday night into Friday.
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Forecasters: Azzara, Munley and Hirsch
Issued: 6:00 p.m., 30 April 2019

Technical Discussion (The nerdy stuff we are discussing in class!)

This week will feature a very active pattern of weather with our main focus this forecast period being on the possible severe thunderstorms that will effect mid-Missouri this afternoon continuing on into tonight.

The big "if" for today was if we were going to see any sun after the round of rain that came through this morning. The answer to that question is yes! The sun was out in Columbia around 19Z and that helps fire up more convection leading to greater confidence of seeing strong to severe storms this evening.

Timing wise, the rain looks to push in from the west ahead of any storms and that should arrive within the next hour or two but the thunderstorms that are of concern will be effecting the viewing area from 23Z-03Z this evening. Reasons for placing the thunderstorms here at this time would be the use of varying indices. Totals totals index is sticking in the upper 40's which promotes thunderstorm development. Using the K-index from around 00Z-04Z has potential for heavy downpours which will lead to flash flooding, which the National Weather Service has placed a watch for until Thursday. The severe threat comes into play around 23Z when severeity the SWEAT index picks up to 369 (meaning severe t-storms potential). The Bulk Richardson Shear at that time will be 99 which is in the index of possible tornadic supercells. While our CAPE and Lifted Index values are not too impressive, the atmosphere will still be moderately unstable which is enough for severe storm possibilities. This system has a great amount of lift to it which rises another concern which will be hail. There is enough updraft for medium sized hail. Strong linear winds are a threat as well, looking at hodographs between 23Z and 02Z the winds are relatively straight-line, rotation is not a huge factor in the winds, causing confidence to skew towards stronger linear winds. Looking at 500mb vorticity, the best circulation over mid-Missouri will be around 02Z however, the circulation will not very strong, also aiding in the higher confidence in straighter winds. There is very low confidence for a tornado to spawn from this system within our forecasting area but via the SWEAT index, there is a marginal threat of a potential tornado after 02Z however, at this point in the evening, there will be extreme shear with BRNS being in the 200's which will tear apart any organized thunderstorms that are present at that time, leaving just heavy rain to follow.

This precipitation is in front a cold front but that cold front will turn into a stationary front that will stick right over Columbia which will drop rain through Wednesday and into Wednesday night. This could have a few scattered thunderstorms associated with it but severity is not of concern because that atmosphere will not be able to rebound enough from the storms from today to convect enough every to make severe storms tomorrow.

Thursday rain will became more scattered and shower like and dissipate into the mid-afternoon hours as the stationary front starts to push off to the east. Clearing is expected into the late afternoon and evening hours but storms could return by late Thursday night and into Friday. Chances for more thunderstorms continue through Friday but confidence on those storms are fairly low but have been increasing over the last few days.

Monday, April 29, 2019



Tonight - Cloudy with thunderstorms developing after midnight. Low: 56-60.



Tuesday - Cloudy with thunderstorms. Storms may be severe, especially after noon. Storms may produce heavy rainfall. High: 68-72.

 

Tuesday Night - Cloudy with thunderstorms ending by dawn. Storms may be severe, especially before midnight. Storms may produce heavy rainfall. L: 60-64.
 

Wednesday - Mostly cloudy with thunderstorms possible in the early afternoon. Storms may be severe. High: 72-76.


 
Thursday - Cloudy. High: 64-68.  



Thanks to IconArchive.com for the icons!




Discussion:
A frontal boundary currently set up over Missouri will move very little between now and Wednesday, and it will act as the focus for several rounds of showers and thunderstorms during this period. Between Tuesday and Wednesday, there will be a heightened risk of severe thunderstorms, with large hail and damaging winds being the main threats. Additionally, any thunderstorms will have the potential to produce torrential rainfall, and with several rounds of thunderstorms in store, localized flooding is possible. By Thursday, the weather shouldn't be as severe as Tuesday and by the evening, skies should be mainly cloudy.

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Forecasters: Danaher and Hirsch
Issued: 6:00 p.m., 29 April 2019

Technical Discussion (The nerdy stuff we are discussing in class!)

WPC recommended a non-NAM model blend because of greater surface pressure drops after Wednesday along the cold front into Ohio Thursday. Therefore, the GFS, SREF, and GEFS will be the models used throughout this forecast period.

Over the next couple days Columbia will mainly experience rain and high wind.
High winds will be the reason we are in the position of a severe thunderstorm from tonight leading into the rest of the forecast period. The jet core north of Missouri and the LLJ will be one of the many contributors that will help the low pressure system over upper Oklahoma and southwest of Texas will influence Missouri.

As Monday night approaches, rain is expected to fall around 03Z Tuesday according to GFS skew-T because of CAPE values at 603 J/kg, LI of negative 4C, CAP of 2C/750mb, negative omega ranging from 800mb to 500mb with the highest being 9 microb/s at 725mb, PW of 1.27", and complete saturation from 900 to 700mb. There is a dry slot between 700mb and 400mb, but forcing for ascent will continue to moisten the layer. By 09Z Tuesday, skew-T shows CAP reaching to 1C/725mb, CAPE increasing to 639J/kg, LI of negative 3C. Winds between 03Z Tuesday to 09Z Tuesday continue to show backing. This not only brings in CAA, but also the flow of moisture as we head into Tuesday for the continuation of severe weather. 

Throughout Tuesday, the flow of moisture occurs because of the LLJ. This will cause a warm front over Columbia as only a little bit of veering from 950mb to 790mb at 12Z Tuesday. However, within hours divergence aloft will sweep over Missouri around 15Z Tuesday causing the winds to shift to backing once again. It will not be until after 18Z Tuesday the warm front has shifted into Northern Missouri. GFS skew-T shows that winds at the surface will be around 40kts between 03Z Wednesday to 06Z Wednesday. This is mainly the reason why we are under a severe thunderstorm threat throughout Tuesday into the night according to the WPC. SREF also notices the threat because the most unstable CAPE happens between 18Z Tuesday to 00Z Wednesday with values at 1598 J/kg. On the other hand, GEFS shows values of CAPE below 1500J/kg and GFS skew-T at 00Z has shown CAPE values of 439J/kg, but with excellent negative omega from 650mb to 500mb with the highest at 600mb at 13 microb/s. So the ability of hail is unlikly while the wind is more so the problem due to the LLJ and south jet streak. Therefore, it does make sense to put out the severe warning due to high winds. However these high winds only last for a couple hours during the night so I believe the warning should be more towards Tuesday night.

By Wednesday, a lot of the convection has eased up. GFS Skew-T does not rule out the possiblity of thunderstorms as could be more into the afternoon. This is because CAPE continues to increase from 1000J/kg at 15Z Wednesday to 3000J/kg at 00Z Thursday, LI staying negative and CAP decreasing back to 0C as it stay between 900mb to 800mb. a dry slot forms and expands from 850mb to 350mb during 12Z Wednesday. Also, saturation continues from 12Z Wednesday to 03Z Thursday. It continues to be in the 700mb to 500mb layer. Only by 06Z Thusday is when the dry slot continues to shrink down to the surface. But it still is able to persist as not rain will fall from 06Z Thursday to 12Z Thursday.

By Thursday, the potential for severe thunderstorm is extremely small as little to no negative omega is present throughout the entire day. CAPE is available throughout 12Z Thursday to 00Z Friday. But without any forcing for ascent, it is unlikely any severe storm will occur over Columbia. However, a lot can change within a couple of days so the next forecast period should look more into it.


Monday -  Cloudy with thunderstorms ending before noon. High: 66-70.



Monday Night - Cloudy with thunderstorms developing after midnight. Low: 56-60.

 

Tuesday - Cloudy with thunderstorms. Storms may be severe, especially after noon. Storms may produce heavy rainfall. High: 70-74.
 

Tuesday Night - Cloudy with thunderstorms ending by dawn. Storms may be severe, especially before midnight. Storms may produce heavy rainfall. L: 60-64.


 
Wednesday - Mostly cloudy with scattered thunderstorms possible, mainly during the afternoon. Storms may be severe. High: 76-80.  



Thanks to IconArchive.com for the icons!




Discussion:
Very active weather is in store for central Missouri over the coming days. A frontal boundary currently set up over Missouri will move very little between now and Wednesday, and it will act as the focus for several rounds of showers and thunderstorms during this period. Between Tuesday and Wednesday, there will be a heightened risk of severe thunderstorms, with large hail and damaging winds being the main threats. Additionally, any thunderstorms will have the potential to produce torrential rainfall, and with several rounds of thunderstorms in store, localized flooding is possible.

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Forecasters: Travis, Ritter, and Hirsch
Issued: 10:30 a.m., 29 April 2019

Technical Discussion (The nerdy stuff we are discussing in class!)
A very active weather pattern is setting up over mid-Missouri. With it will come the threat of heavy rain, thunderstorms with the potential for severe storms. As per WPC's recommendation of a non-NAM model blend, went primarily with GFS and SREF guidance due to their coverage of the entire period. For short term CAMs, went with the HREF ensemble. The main issue with this active period is analyzing the threat for severe weather and flooding across the state. 

Monday morning, radar showed a line of heavy rain moving east through the state, exiting Columbia shortly after 12z. Behind it, GOES IR imagery shows partial clearing over the eastern half of the state and sky cameras from KRCG 13 back this up. This shot of sunshine will allow our temperatures to surpass what 06z model output suggested. For this reason, we went slightly higher with Monday's high than model guidance suggests. As the sun comes up, we now have GOES VIS imagery available. Visible satellite suggests that this partial clearing will not stick around for long. As this line moves further off to our east, the chance for precip later in the day diminishes. Looking at paintball plots of >40 dBZ from the HREF, some members plot isolated showers to our south in the Missouri Ozarks. However, looking at the current surface map from the WPC, the cold frontal boundary to our west and the stationary front well to our south in Arkansas should keep this precip to our south. 

Monday Night, our chances of precipitation return. At 250 hPa, the GFS has an area of strong divergence moving northeast into Missouri at 06z Tuesday. As the night progresses, divergence intensifies and becomes more widespread over central Missouri. Stepping down to 500 hPa, the GFS has a small, but intense vorticity maximum propagating into mid-Missouri. This will follow the general flow as Missouri sits in the inflection point of the 500-hPa trough to our west and ridge to our east. Overnight Monday, moisture and lift is on the increase according the GFS 700-hPa hgt, RH, and omega. This is all due to a strong LLJ analyzed at 850 hPa. After briefly quieting down during the day Monday, the LLJ ramps back up at 06z Tuesday. Maximizing over mid-Missouri at 50 knots Tuesday night into Wednesday. This will bring more than enough warm moist air from the Gulf of Mexico, into the Midwest to fuel thunderstorm development. The GFS Skew-T at 06z Tuesday shows a completely saturated layer from 700 hPa down to the surface, with negative omega existing at this saturated layer. This, combined with 928 J/Kg of MUCAPE, leads to likely rumbles of thunder throughout the night. 

Tuesday, the potential for showers and thunderstorms remain. GFS Skew-Ts show brief drying of the PBL after 18z. We stay dry until after 00z when a fully saturated column with ample lift returns. Again, thunderstorms over night Tuesday appear likely, with well over -10 ubar/s of lift depicted by the Skew-T at 06z. The most unstable parcel also drops considerably from Monday night, lifting from ~925 hPa, making surface based convection all the more likely. 

Wednesday day, we see an impressive set up for severe convection. As soon as the sun comes up on Wednesday, the atmosphere wastes no time destabilizing. GFS Skew-T for 12z Wednesday already have characteristics of a "loaded gun" with a warm moist surface, lift at the surface, and 850-500-hPa lapse rates of -7.3 C/Km. Surface based CAPE is valued at 929 J/Kg with CIN of 80 J/Kg. One issue mid-Missouri might face is the potential for thunderstorms firing too early in the morning. By Wednesday afternoon it is likely there will already be widespread thunderstorm activity. By 00z Thursday, soundings show a surface based CAPE of 2900 J/Kg with no CIN. The Bulk Richardson number at this timestep is 114. The extremely high CAPE, and low shear will make it harder for supercellular activity to thrive, at least over mid-Missouri. What appears more likely is a strong QLCS taking shape over Missouri possibly bringing with it, strong winds and hail. The SPC has Columbia just outside of a slight risk for Day 3. Seeing as this is a Wednesday afternoon event, the potential for severe is still up in the air. Will defer to later shifts to analyze the specifics, and the threat going forward into this week.

The threat of flooding persists with this system as well. GEFS mean of QPF favors the potential for over 3 inches of rain by the end of our period. SREF is lower, favoring only about 2 inches. Regardless, both scenarios will have the potential to result in messy flooding across the state. LSX already has Boone County under a hydrologic outlook. Again, will defer to later shifts to better narrow down the flooding threat as the week progresses.