U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 240550 
Storm Prediction Center ac 240548 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1248 am CDT Sat Mar 24 2018 

Valid 241200z - 251200z 

..no severe thunderstorm areas forecast... 

thunderstorms are possible today -- mainly across the Ohio Valley 
and mid south, and over portions of the western states. 

Eastward progression of the upper flow field over the U.S. Is 
expected today as an upper low/trough just off the Pacific northwest 
coast at the start of the period moves gradually inland. A 
shorter-wavelength disturbance will cross the Midwest/Ohio Valley 
region, eventually becoming absorbed into the larger-scale cyclonic 
flow persisting over the northeast through the period. 

At the surface, low pressure initially over the Missouri vicinity is 
forecast move east into the mid south, weakening with time. 
Meanwhile, gradual progression of a cold front is forecast over the 
interior west, ahead of the advancing upper trough. 

Showers and scattered thunderstorms can be expected over parts of 
the west, as the aforementioned system progresses. Farther east, 
showers and storms are expected across the mid Mississippi and lower 
to middle Ohio Valley, and into the mid south region, in conjunction 
with the weakening surface low. In all areas however, severe 
weather is not expected. 

.Goss/Gleason.. 03/24/2018 


Mesoscale Discussion

acus11 kwns 240103 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 240102 

Mesoscale discussion 0169 
National Weather Service Storm Prediction Center Norman OK 
0802 PM CDT Fri Mar 23 2018 

Areas affected...portions of eastern South Dakota...southwestern Minnesota...and 
northern Iowa 

Concerning...heavy snow 

Valid 240102z - 240700z 

Summary...a band of heavy snow will develop through the evening, 
with snowfall rates around 1 inch per hour likely. 

Discussion...a band of rain/thunderstorms across southeastern South Dakota 
into northwestern Iowa as of 01z is being supported by lift associated 
with a shortwave trough ejecting northeastward over the 
northern/Central Plains. A strengthening southeasterly low-level jet 
will increase in the thermal gradient around 850 mb. Although some 
sleet may occur initially, forecast soundings from the NAM/hrrr 
suggest mid-level cooling with the approach of the shortwave trough 
will encourage a fast transition from rain to snow across eastern South Dakota 
into southern Minnesota and northern Iowa as ongoing precipitation shifts 
into this area through 03-05z. 

A band of heavy snow will develop across this region later this 
evening into the early overnight hours, with strong low-level 
frontogenetic forcing and deep ascent occurring through the 
dendritic growth zone likely supporting snowfall rates around 1 inch 
per hour. Some localized higher rates to around 2 inches per hour 
may be possible within convective elements of the band, and an 
isolated lightning strike or two cannot be ruled out. Of note, there 
will likely be a sharp northern gradient to the heavy snow due to a 
residual dry low-level airmass being reinforced by strong 
east-northeasterly surface winds across parts of central/eastern Minnesota. 

.Gleason.. 03/24/2018 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 44179713 44569745 45219736 45639677 45579617 45379555 
45039488 44619427 44229364 43929318 43529272 43089247 
42759242 42569291 42969378 43329480 43449561 43709648