U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 230528 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1128 PM CST Tue Jan 22 2019 


Valid 231200z - 241200z 


..there is a slight risk of severe thunderstorms along the central 
Gulf Coast... 


... 
Isolated severe thunderstorms are expected along portions of the 
central Gulf Coast with some severe threat surrounding this area as 
far east as the northern Florida Peninsula late in the period. 


..Gulf states... 


Late-evening water-vapor imagery depicts a low-latitude short-wave 
trough over far West Texas/northern Mexico digging east-southeast 
toward the Texas coast. Thunderstorms have recently developed ahead of 
this feature in response to large-scale forcing for ascent that is 
spreading across south-central Texas. Latest guidance suggest strong 
mid-level height falls will develop across the central Gulf states 
ahead of this feature which should encourage a weak surface low to 
evolve along associated cold front over the lower MS valley early in 
the period. Boundary-layer moisture is not particularly high across 
the central Gulf Coast but should increase during the morning hours 
with mid 60s possible prior to frontal passage. Latest thinking is a 
forced line of storms should evolve along the wind shift by mid-late 
morning then advance east ahead of the progressive trough. 
Strengthening shear profiles will favor sustained organized squall 
line that should advance toward the Florida Panhandle by late afternoon. 
While storm Mode should be primarily linear, a few supercells could 
evolve immediately ahead of the line, or embedded within the frontal 
convection. Locally damaging winds are the primary threat but one or 
two tornadoes could develop near the coast. During the overnight 
hours, low-level trajectories will become more favorable for 
somewhat higher Theta-E air mass to return to the Florida Peninsula. This 
air mass recovery will prove favorable for continuation of frontal 
squall line and attendant severe threat with strongly sheared 
convection. 


.Darrow/Gleason.. 01/23/2019 


$$ 

Mesoscale Discussion


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acus11 kwns 230001 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 230000 
miz000-ohz000-inz000-230600- 


Mesoscale discussion 0045 
National Weather Service Storm Prediction Center Norman OK 
0600 PM CST Tue Jan 22 2019 


Areas affected...portions of northern in...Southern Lower Michigan...and 
far northwestern Ohio 


Concerning...freezing rain 


Valid 230000z - 230600z 


Summary...generally light freezing rain should continue through much 
of the evening, with rates up to 0.05 inch per hour. 


Discussion...strong warm air advection is occurring with a 40-60 kt 
southwesterly low-level jet from the mid MS valley into the lower 
Great Lakes region this evening. Related isentropic ascent atop a 
shallow sub-freezing layer near the surface is contributing to light 
precipitation in a 100-125 mile wide zone from eastern Illinois into 
northern in, southern lower mi, and far northwestern Ohio. Surface 
observations over the past several hours indicate light freezing 
rain has been the dominant precipitation type so far across this 
region, as a shallow above freezing layer generally between 850-800 
mb per rap forecast soundings melts frozen hydrometeors aloft. This 
light freezing rain is expected to persist for at least a couple 
more hours as the 0c isotherm at 850 mb should only gradually shift 
northward across Southern Lower Michigan through 06z. Ice accretion rates 
up to 0.05 inch per hour have already been observed at several 
sites, and this trend should continue for several more hours. 
Eventually, gradual warming at low levels will likely result in a 
transition to rain as surface temperatures slowly increase above 
freezing from south to north. 


.Gleason.. 01/23/2019 


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


Attention...WFO...cle...DTX...iwx...GRR...lot... 


Latitude...Lon 41118663 41368745 41678744 41718704 41958659 42298632 
42438548 42718415 42988302 43018248 42618243 42318296 
42058310 41628327 41268391 41188496 41118663