Wednesday, April 8, 2020

Severe Thunderstorm Watch in effect from 3:05pm until 9:00pm.

Wednesday Night- Decreasing clouds, severe thunderstorms possible 
early evening. Low: 40-44

Thursday- Partly cloudy. High: 54-58

Thursday Night- Mostly clear. Low: 28-32

Friday- Mostly sunny. High: 54-58

Saturday- Mostly cloudy with rain possible. High: 56-60

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A severe thunderstorm watch remains in effect until 9 PM. This evening, scattered thunderstorms -- some severe -- will form along a cold front passing over central Missouri. After it passes through, clouds will move out and temperatures will drop. These colder temperatures, courtesy of northerly winds behind the front, will stay with us over the next several days as a high pressure system builds in. Even though we will experience cooler temperatures, that high pressure system will maintain mostly sunny skies. Go out and enjoy the sunny skies, because Saturday will bring our next chance for rain and cloudy skies as winds become southerly and begin to bring in moisture.
Forecasters: Vanderpool, Pauley, Heaven
Issued: 5:00pm April 8, 2020

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

Model Diagnostics from the WPC recommends a general model blend of the GFS/NAM/ECMWF.

The biggest issues in the near term include very warm temperatures and the risk for severe weather in central MO. A severe thunderstorm watch is in effect until 9 pm CDT for Columbia and points east. Plenty of agitated cumulus are showing up on visible satellite in mid-MO, with a developing line of convection approximately 30 miles northwest of Columbia as of 4:15 pm CDT. 

20z RAP analysis reveals a very unstable atmosphere in central MO. MUCAPE values near 3000 J/Kg - maximized over Columbia - are coincident with minor veering in the lower layers of the atmosphere. Hodographs suggest storm motion from the WNW at ~25 kt, which appears to be verifying based upon latest WSR-88D data. Convection is currently limited to a few showers developing along the frontal boundary to the northwest of Columbia, but given very high CAPE and relatively calm winds (< 50 kt) below 500-mb, these will likely grow upscale into scattered, fully-fledged thunderstorms over the next hour or two. Not every storm will become severe, and many may struggle somewhat to reach severe levels. However, upscale growth will continue to be fed by a narrow corridor of low-level moisture pooling ahead of the approaching cold front. Primary threats will be large hail and damaging winds, with emphasis on the damaging downburst winds considering the substantial amount of dry air present in the lower and middle troposphere. Hail up to a couple inches in diameter is also possible, especially when taking into account evaporative cooling in the storm downdrafts and the very large CAPE values in place. It is possible that convection may become cold-pool dominant within a few hours after formation, which would lead to a transition towards a greater wind threat later on in the evening. Should this occur, it would likely be after storms clear the Columbia area. Short-range CAMs including the HRRR and NAM 3-km validate this prognosis, with the 20z HRRR forecasting rapid convective development in the severe watch area between 22z and 00z. 

Prognostically, high-res models show that the incoming front is rather messy and ill-defined. The 20z HRRR and 18z NAM 3-km both agree that surface moisture should scour out between 00z and 02z. Thus, the true sfc FROPA will probably occur sometime within that time frame. Convection is likely to grow upscale between now and then, with some storms becoming severe, before moving out of the Columbia area around or shortly after 00z. 

Tonight, the aforementioned cold front -- associated with a positively-tilted trough axis at the surface -- will move southeast, firmly entrenching mid-MO in a regime of strong cold air advection. It will be strong enough to cause a 40+ degree drop between daytime highs today (Wednesday) and early-morning lows tonight. 

For Thursday and Friday, high temperatures will hover in the 50s -- about 5-10 degrees below climatological averages -- with mostly sunny skies. This chilly and tranquil weather will be brought into the region courtesy of a strong surface high with a Canadian origin. Current indications are that continued cold air advection and radiational cooling will cause temperatures to drop below freezing (and possibly several degrees below freezing) for Thursday night, which appears to be our coldest night of the forecast period. 

On Saturday, things will get a bit more interesting as lee cyclogenesis produces a panhandle hook type low pressure system. Out ahead of this low, temperatures should warm into the upper 50s to lower 60s for highs as warm air advection kicks in. This will also support overcast skies and a decent chance for rain. Currently, instability looks rather lacking, so this activity is unlikely to be severe. February-like weather looks to return on the backside of this low, with an extended period of much below normal temperatures likely beginning early next week. 

Tuesday, April 7, 2020

Tuesday Night - Partly Cloudy. Low: 56-60

Wednesday - Sunny. High: 78-82

Wednesday Night - Possible storms in the evening, overnight clearing. Low: 38-42

Thursday - Sunny. High: 54-58

Friday - Sunny. High: 54-58

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The clear skies and above average temperatures that we are getting will continue for
tomorrow as well. This is because of a strong ridging pattern that is situated over the
central part of the country. Tomorrow evening, the ridging pattern will move off to the
east which will bring in a cold front and a chance of some rain and storms along the front.
After the passage of the front, skies will clear. This will cause temperatures for Thursday and
Friday to be as much as 25 degrees colder than they previously were on Wednesday.
Forecasters: Gallahan, Munley
Issued:  5:00pm: April 7, 2020

Technical Discussion (The nerdy stuff we are discussing in class)
Model preference calls for a non-12z NAM blend. Decided to go with the 12z GFS due
to it matching well with current observations.

The main topics of this forecast period are the clear skies and above average
temperatures that will last until tomorrow evening. A potential for rain and storms
associated with the passage of the front, and lastly a sharp temperature drop
off for Thursday and Friday also associated with the frontal passage.

The unseasonably warm and sunny day that occurred today will occur again tomorrow.
This is due to a ridging pattern occurring at the 250mb level. This ridging pattern is the
driving force for these unseasonably warm temperatures. Looking ahead for tomorrow
evening, 500mb vorticity indicates a shortwave coming into the area around 00z Thursday
morning. This along with an increase in 700mb RH and UVM indicate a frontal passage
and potential rain and storms. As of right now, due to the lack of SBCAPE and low level
support, nothing strong to severe looks to come out of them, just rain and a potential
storm. A change in wind direction occurs late tomorrow evening as a backing wind profile
will occur which will clear skies and usher in CAA which will drop temperatures for
Thursday and Friday nearly 25 degrees.

Monday, April 6, 2020

Monday - Cloudy. High: 70-74


Monday Night - Cloudy. Low: 58-62

Tuesday - Mostly cloudy. High: 78-82


Tuesday Night - Decreasing clouds. Low: 54-58

Wednesday - Mostly sunny. High: 78-82

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Above average temperatures will dominate this forecast period. A warm front is 
expected to push north of Missouri today, allowing for winds to shift out of the south
and bring in moisture from the Gulf of Mexico. Low-level clouds are expected to 
persist through today and most of tomorrow, finally diminishing tomorrow night after 
winds shift out of the southwest. This shift to the southwest will result in less moisture 
being pulled into the area, allowing for clouds to dissipate. Tuesday and Wednesday 
may feel a little muggy outside since temperatures and relative humidity are so high. 
There is a slight chance for some isolated thunderstorms to form Wednesday afternoon 
if all of the ingredients are in place, but as of right now, this does not look very likely.

Forecasters: Clemons, Farr, Heaven
Issued:  10:00am: April 6, 2020

Technical Discussion (The nerdy stuff we are discussing in class)
The highlights for this forecast period includes unseasonably high temperatures and 
the possibility for surface-based convection. As prompted by the WPC, we used a 
general model blend for this forecast period, specifically using the 06Z NAM and GFS. 

Starting at 250mb, we are currently in the left exit region of the subtropical jet. This may
help support some convergence at the surface. We remain in this region until Tuesday 
morning when the jet max sets up right over Missouri. This jet is set up in accordance 
with an overall ridging pattern aloft. The axis of this ridge will be right overtop of Missouri 
as well Tuesday morning around 12Z. After that, things level out and become zonal for 
the rest of the forecast period. This setup is also reflected at both 500mb and 700mb. 
RH values are relatively low from 700mb up. Synoptically, this does not provide a lot of 
support for anything other than calm weather through our forecast period. That being said,
most of the weather affecting us the next several days will be surface based with little to no 
upper lever support. Around 850mb, we begin to see massive southerly flow which is going 
to advect warm moist air over the area as the LLJ sits right over us. This moisture will 
affect us in the form of cloud cover today and tomorrow. Tuesday, winds begin to shift
easterly and we begin to dry out leading to a sunnier day on Wednesday.

Due to forecasted high temperatures and moisture advection, surface based convection is 
possible Monday through Wednesday. However, with no evident forcing mechanisms the 
possibility of any convection breaking the cap is extremely low. Wednesday afternoon and 
evening seems to be the best chance for storms as a cold front is forecasted to move across 
Columbia from the northwest. Soundings right after FROPA indicate support for elevated 
convection, unlike the surface-based instability shown for today and tomorrow. Surface CAPE 
values prior to the cold front passage on Wednesday are forecasted to be around 3000J/kg, 
along with sufficient moisture. The sounding also shows lapse rates near 8 C°/km. All of these 
indicators suggest supported upper level convection; however, future forecasters should be 
made aware of this development as the timing and intensity are not well known at the time.

Friday, April 3, 2020

Friday Night - Cloudy with rain. Low:36-40

Saturday - Partly cloudy. High: 52-56

Saturday Night - Overcast. Low: 40-44

Sunday - Partly cloudy. High: 62-66

Monday - Partly. High: 72-76 

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Rain is expected Friday night from about 6pm until midnight. This rain should be the 
only precipitation expected to fall during the forecast period. Clouds will be sticking 
around for the rest of the weekend, never fully clearing. Lower level clouds should be 
expected due to the moisture at the lower levels. Temperatures will be warming 
throughout the weekend into the week, due to winds coming from the south.
Forecasters: Balkissoon, Savoy, Heaven, Munley
Issued:  5:00pm: April 3, 2020
Technical Discussion (The nerdy stuff we are discussing in class)

WPC suggested a GFS/ECMWF blend for this forecast period so as a group, 
we decided to go with GFS. SREF plumes were also used during this forecast 
period to help verify temperature and precipitation amount. 

From the 250-hPa divergence map, we note that at 18Z (the time of our current 
forecast), we sit north of the jet.  This can account for our lower temperatures 
that we are experiencing now. As we move through the weekend, however,
there are no significant periods where upper level divergence was noted.  Hence
the upper levels in the atmosphere did not show conditions conducive for 
precipitation at the surface.  

From the 500-hPa vorticity and heights map.  Currently, a low pressure system 
is noted to be situated to the NW of our forecast region and there is a shortwave 
ridge that has moved past us.  Stepping through the weekend, the flow is relatively 
zonal with no significant circulation. However, it is worth mentioning that there is a 
low coming in from the Pacific which is not yet matured.  This positively tilted trough 
should be monitored by future forecasters as it may affect our weather in the coming
days ahead. 

Next, we move down to 700-hPa relative humidity and omega maps. We noted at 
18Z we have high RH values (%80-%100) but as we move on into the weekend, 
RH continues to decrease. We did note significant moisture off to our south, but it 
should not be influencing us during our forecast period. Looking at omega we noted 
smaller values at 18Z that continue to increase into 21Z, during this period we are 
expecting some rain. After this rain however, values decrease into the weekend and 
do not increase again in our forecasting period.  This was also supported with GFS 
skew-T analysis.

At 850-hPa we looked at temperatures but unfortunately could not load winds to help 
verify what we’re looking into. We have temperature remaining consistently above 
freezing with a nice warm up throughout the weekend into the beginning of the week, 
starting in the mid 50’s and reaching in the mid/lower 70’s by Monday afternoon. We 
do believe this warm up is due to the low coming off the west coast, as mentioned 
earlier but could not verify without wind to check for warm air advection. 

Thursday, April 2, 2020

Thursday Night - Cloudy with showers possible. Low: 52-56

Friday - Cloudy with rain likely. High: 58-62

Friday Night - Cloudy with rain. Low: 36-40

Saturday - Decreasing clouds. High: 52-56

Sunday - Partly cloudy. High: 62-66

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Cloudy skies will continue Thursday night into Saturday night due to a low pressure system moving through the Midwest. Showers are likely Thursday evening into Friday. Rain is likely Friday, mainly after noon. A cold front is expected to move through Columbia late afternoon into the early evening hours on Friday bringing overnight temperatures down to the upper 30s. Rain is anticipated to stop very early Saturday morning leading to cloudy skies for the first half of the day. Partly cloudy skies return Saturday afternoon through Sunday. (CD)

Forecasters: Lieberman, Dowell, Ritter
Issued:  6:00PM: April 2, 2020

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

We used the GFS and NAM supplemented with SREF and GEFS. The model diagnosis from the WPC recommends a non-UKMET blend for this forecast. (CD)
From the top down and beginning with 250MB, Missouri is currently in zonal flow with a small ridging action in Iowa and northward. A trough is stretched from Alberta to southern Nevada with a jet streak stretching from Wichita Falls, TX, through Savannah, GA. At 500MB, both the trough and ridge are more defined and the ridge is currently east of Columbia. Additionally, there is some circulation to the west At 700MB, central Missouri does not have an abundance of moisture, currently 50-60 percent RH. At 850MB, low levels are supporting moisture transport into Missouri. (CD)
At the surface, a cold front extends from a low pressure system in central Minnesota down to central Kansas. (CL)
Looking forward to tonight, circulation associated with a weak trough at 500MB and the low pressure system to the north will move into Columbia. At the same time at 850MB, southerly winds associated with the low level jet will advect moisture into the area. This will lead to moderate precipitation this evening into tomorrow morning. Then, at approximately 18Z on Friday, the aforementioned cold front extending from the low pressure system over the northern Midwest will pass over Columbia. This will produce continued precipitation until early in the morning on Saturday. Soundings throughout this period show low level saturation and moderate lift. Significant instability is limited to south of Missouri. The maximum CAPE values shown on soundings for Columbia do not reach even 500 J/Kg. This makes convective precipitation a possibility but thunderstorms are very unlikely. Overnight, northerly winds and evaporating precipitation mean that temperatures will drop into high thirties. (CL)

Saturday, moisture and clouds will clear out as dry air is advected from the southwest. The low pressure system to our north will weaken and zonal flow will set in over the midwest. At the surface, high pressure will set in and temperatures will warm into the mid 50’s. This trend will continue into Sunday as pressure and temperatures increase throughout the day. (CL)