U.S. Severe Weather Forecast (Convective Outlook)

نن، نن ورځ: نن، نن سبا
سبا: سبا، ګانده: راتلونكى وخت
Day Three

000 
acus01 kwns 211913 
swody1 
Storm Prediction Center ac 211912 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0112 PM CST Wed Feb 21 2018 


Valid 212000z - 221200z 


..there is a slight risk of severe thunderstorms from central 
Louisiana into western Mississippi... 


..there is a marginal risk of severe thunderstorms from the Sabine 
River into central Mississippi... 


... 
Thunderstorms will continue from Texas today to the Ohio Valley and 
Appalachians today into tonight, some of which will be associated 
with freezing or frozen precipitation across northwest Texas and 
Oklahoma. A couple of tornadoes and isolated strong wind gusts will 
be possible with the storms across Louisiana and adjacent areas of 
southeast Texas and west central Mississippi. 


..Louisiana into western Mississippi... 
A primary cluster of storms continues to evolve over central la, 
moving slowly northeastward ahead of a slow-moving front. Trends 
indicate these storms have evolved into a small MCS, with embedded 
supercells. A tornado or two along with wind damage remains 
possible, and the presence of warming air downstream may enhanced 
the potential for a few hours. The area immediately ahead of or 
along the front may be a preferred corridor. However, this front 
will also demarcate the northern extent of the threat area. While 
other isolated cells may form farther south of the main cluster, 
low-level shear is not quite as strong, with a relatively lesser 
threat. For more information see mesoscale discussion 81. 


.Jewell.. 02/21/2018 


Previous discussion... /issued 1004 am CST Wed Feb 21 2018/ 


..lower MS valley and Southern Plains through tonight... 
A deep warm/moist conveyor belt is established from the western Gulf 
of Mexico into the lower MS valley, along and immediately southeast 
of a slow-moving cold front. The pattern will change little through 
tonight as the large-scale ridge persists over the southwest 
Atlantic and at least two shortwave troughs continue to dig 
southward/southeastward along the Pacific coast to maintain the mean 
western trough. Within the warm conveyor belt, a maritime tropical 
air mass (boundary layer dewpoints near 70 f) will continue to 
spread northward across la/MS today, with some surface heating 
possible along the southeast periphery of the ongoing warm sector 
convection. The storms are likely to persist through the day in 
this moist and uncapped environment per regional 12z soundings, 
where deep-layer vertical shear will be sufficient for supercells 
within the larger storm clusters. Given the rich low-level moisture 
and effective srh in excess of 200 m2/s2, a couple of tornadoes will 
be possible, along with isolated strong wind gusts. 


Otherwise, a swath of elevated convection will continue above the 
shallow cold air mass across the Southern Plains. The boundary 
layer will be sufficiently cold for a mix of sleet and freezing rain 
with the elevated convection from northwest Texas into southern OK 
today through early tonight. 


$$ 

Mesoscale Discussion


000 
acus11 kwns 212301 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 212301 
moz000-arz000-okz000-ksz000-220400- 


Mesoscale discussion 0084 
National Weather Service Storm Prediction Center Norman OK 
0501 PM CST Wed Feb 21 2018 


Areas affected...portions of northeast OK...extreme southeast 
Kansas...southwest and central MO and extreme northwest Arkansas 


Concerning...winter mixed precipitation 


Valid 212301z - 220400z 


Summary...light freezing rain, mixing with sleet and snow at times, 
will expand northeast from northeastern OK into southwestern and 
central MO this evening. Freezing rain rates are expected to remain 
light. 


Discussion...light precipitation is expanding northeast, roughly 
along the I-44 corridor from northeast OK into southwest MO early 
the evening. Weak forcing for ascent and warm advection will be 
sufficient for continued light precipitation expanding northeast 
with time through the evening. Surface temperatures across the mesoscale discussion 
area ranged from around 27 to 30 degrees f as of 23z. The surface 
cold front may slosh westward a bit this evening, but temperatures 
are expected to remain below freezing. Forecast thermodynamic 
profiles will mainly favor light freezing rain, though some sleet 
and/or snow could mix in at times. The lack of stronger forcing for 
ascent should limit precipitation rates, and freezing rain rates at 
or below 0.05 inches per 3 hours are expected. 


.Leitman.. 02/21/2018 


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


Attention...WFO...lsx...sgf...tsa...ict... 


Latitude...Lon 36719569 36519604 36299624 36079632 35839624 35579584 
35549556 35659515 36059431 36829257 37409129 37679114 
37919118 38079133 38189153 38249180 38259204 38199233 
37539409 37209480 36719569