Friday, April 10, 2020

Friday Night - Increasing clouds. Low: 42-46

Saturday - Partly cloudy.  High: 66-70

Saturday Night - Overcast. Low: 56-60

Sunday - Overcast, with possible thunderstorms. High: 68-72

Monday - Decreasing clouds through the day, with early morning rain. High: 46-50
 Thanks to for the icons!

We have increasing temperatures throughout the weekend, but as a low pressure system from the north  moves in 
temperatures will drop into Monday. We expect chances of convective storms from late Sunday into early Monday 
as we will be influenced by another low pressure system which is coming in from the Pacific.  Clouds will remain 
throughout the forecasting period but will begin to decrease late into Monday after our chances for rain and 
thunderstorms have passed. 

Forecasters: Balkissoon, Savoy, Heaven
Issued:  5:00pm: April 10, 2020
Technical Discussion (The nerdy stuff we are discussing in class)

WPC model diagnostics suggested a general model 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. 

Looking at the 250-hPa winds and height map, we noticed a ridge off to our east 
making its way over us. As this ridge moves off to our east, a positively tilted trough 
moves in to take its place. This trough passes over us late sunday night into monday 
morning, as a fully matured system. As we move down in the lower levels we can 
see the effects of the upper level trough. 

From the 500-hPa Vorticity and heights map, we observed this positively tilted trough 
coming in from the Pacific on Saturday at 9Z.  On Sunday at 18Z it becomes matured 
as we see with this system, circulation over our area around Sunday 21Z of numeric 
absolute vorticity value 34/s.  On Monday at 3Z the max of this scale is noted for SE 
Missouri. This system clears out around Monday at 15Z, making way for a deep low 
coming in from Canada in which circulation is once again observed over our domain.  
Next we move to 700 hPa, here we took a look at relativity humidity values and vertical 
velocity. As of right now, Missouri is dry as a bone but RH values will increase into 
Saturday and those higher RH values (%80-%100) will continue into Monday. Values 
will then begin to decrease on monday around 15Z and continue to decrease into the 
next forecasting period. During our period of high RH we also have increased vertical 
velocity, with increased values beginning Saturday at 18Z and reaching the highest 
values of +40 -ubs^-1 on Monday at 0Z, which will be the ideal timing for thunderstorms 
and rain.

From the 850-hPa map of winds and temperature.  We observed an increasing trend 
of temperature values this weekend as the wind is blowing warm air from the south.  
The temperature ranges from the GFS run is a bit lower than the SREF temperatures 
given above. It also gives sub-zero celsius temperatures on Monday as colder air is 
blowing from the north due to the deep low.  

Over our region the GFS run places our accumulated precipitation in the amount of 
0.02 inches for Saturday.  This increases to 0.36 inches on Monday at 0Z with max 
accumulation of 0.84 inches at 21Z on this said day. The GFS accumulations are 
higher than the SREF outputs for Sunday and Monday which are 0.24 and 0.70 inches 

We also took a look at some of the convective products.  The Energy Helicity Index 
(EHI) for Columbia was monitored.  The max EHI was observed at 18Z on Sunday. 
Its value was 0.7, which is a little lower than the EHI of 1 for possible tornadoes.  Also, 
the max SRH for Columbia during our forecast period was 104 which is not in the 
required range for possible supercells (range is between 150 and 299).

We then looked at Skew-T’s which seemed to deviate from what we had gathered in 
our top down approach. In the area we choose near Columbia, we have full saturation 
from the lower levels into the mid/upper levels but are lacking instability and lift. The area 
we chose for Skew-T’s is lacking but all surrounding areas have the necessary ingredients 
for a thunderstorm. It will be important for future forecasters to look at this and monitor the 
situation. We also looked at SPC thunderstorm risk and they have Columbia at marginal 
risk with 5% severe probability for the time period of Sunday afternoon into Monday early 
morning .

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