U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 221948 
Storm Prediction Center ac 221946 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0146 PM CST Tue Jan 22 2019 

Valid 222000z - 231200z 

..no thunderstorm areas forecast... 

thunderstorm potential will remain low across the United States 
through tonight. 

..20z outlook update... 
Latest model output and observational data provide no substantive 
support for change of ongoing forecast of less than 10 percent 
thunderstorm probabilities through 12z Wednesday morning. 

.Kerr.. 01/22/2019 

Previous discussion... /issued 1018 am CST Tue Jan 22 2019/ 

A positive-tilt midlevel trough will progress eastward over the 
central/Southern Plains toward the MS valley through early 
Wednesday, as an associated surface cyclone develops northeastward 
from OK to the mid MS/lower Ohio Valley region. Low-level moisture 
return in the warm sector will continue through the period, though 
moisture increases will be slow given the prior frontal intrusion 
through the entire Gulf and western Caribbean basins. This 
moistening will occur beneath a warm elevated mixed layer and strong 
cap per regional 12z soundings. There is a small chance for 
sufficiently deep buoyancy for lightning production with elevated 
convection will be across parts of Arkansas/MO tonight in the strong 
low-level warm advection zone, though cape will remain limited 
(around 100 j/kg) with cloud tops mostly warmer than -15 to -20 c. 
Other isolated midlevel convection rooted above 700 mb may occur 
overnight across south Texas. However, given the marginal moisture 
return and warm profiles aloft to limit buoyancy, the prospects for 
thunderstorms still appear too low for any outlook areas. 


Mesoscale Discussion

acus11 kwns 222037 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 222036 

Mesoscale discussion 0044 
National Weather Service Storm Prediction Center Norman OK 
0236 PM CST Tue Jan 22 2019 

Areas affected...eastern Iowa...northern Illinois and far southeast 

Concerning...freezing rain 

Valid 222036z - 230030z 

Summary...light to moderate freezing rain is overspreading much of 
eastern Iowa, northern Illinois and far southern Wisconsin. 

Discussion...freezing drizzle has been falling for most of the day 
across the Maryland area with ice accretion rates around 0.01 to 0.03 
inches per hour. Ice accumulation has shown to be efficient so far 
with ice accretion at least twice the water equivalent at most 
observing sites. This efficient icing is likely due to a combination 
of light precipitation rates, well below freezing surface 
temperatures, and winds around 10 to 15 mph. These rates will be 
increasing over the next few hours as heavier precipitation spreads 
from west to east. The first signs of these increasing rates can be 
seen on radar in southeast Iowa and western Illinois as well as 
central Illinois. 

Precipitation is currently falling as freezing drizzle/freezing rain 
across the entire Maryland area as the dgz is yet to saturate across 
northern Illinois and southern Wisconsin despite the entire column 
being cold enough to support snow. Therefore, expect precipitation 
to change to snow in these areas as the column saturates and 
precipitation rates increase within the next few hours. The href 
shows very little movement of the warm air aloft through the 
evening, so the rain/snow line is expected to stay within a County 
either side of the 0c 850mb line on the graphic. 

The timing of this heavier freezing precipitation will coincide with 
the evening commute across the highlighted area including the Quad 
Cities, Chicago, Rockford, and Milwaukee. In addition, Road 
conditions are expected to worsen after dark as the warming effects 
of filtered sunlight go away and precipitation rates increase. 

Through time, surface temperatures are expected to increase south of 
the rain/snow line which will eventually end the freezing rain for 
most areas and result in snow north and rain south by late this 

.Bentley.. 01/22/2019 

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


Latitude...Lon 40389127 40549160 40709194 41169186 41449160 41779107 
42419019 42638968 42808873 42738814 42698779 42518779 
42398777 42238775 42138764 41968756 41848749 41728742 
41598740 41428747 41288796 41148850 41038909 40838939 
40678968 40559002 40479043 40379084 40389127