U.S. Severe Weather Forecast (Konvektiivne väljavaade)

Day Three

acus01 kwns 251605 
Storm Prediction Center ac 251604 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1104 am CDT Mon Jun 25 2018 

Valid 251630z - 261200z 

..there is a slight risk of severe thunderstorms this 
afternoon/evening from Iowa into MO...and from the southern 
Appalachians across parts of the Carolinas... 

Isolated severe thunderstorms are possible across Iowa, Missouri and 
far eastern Nebraska today, while other severe thunderstorms are 
expected across the southern Appalachians vicinity and Carolinas 
during the afternoon and evening. 

..IA/MO area this afternoon/evening... 
A closed midlevel low over the southwest NE/northwest Kansas border will 
drift generally eastward toward Iowa/MO by the end of the period, as 
an upstream shortwave trough crosses the northern rockies. At the 
surface, a weak cyclone will move northward from northeast Kansas to 
eastern NE as an embedded speed Max rotates around the NE closed 
low. A diffuse warm front will move northward with the surface 
cyclone, and a belt of southeasterly low-level flow (30-40 kt at 850 
mb) will be maintained along the warm front. Assuming enough cloud 
breaks occur to allow destabilization along the fringe of the 
ongoing band of rain and thicker clouds, there will be some 
potential for supercells and a couple of tornadoes this 
afternoon/evening across southern/central Iowa. 

Farther south, a corridor of low-mid 70s boundary-layer dewpoints 
will be maintained along the MS river, to the south of a synoptic 
front and southwest of early convection and a weak mesoscale convective vortex moving 
eastward over the lower Ohio Valley. Some cloud breaks by this 
afternoon will allow surface temperatures to warm well into the 80s, 
resulting in afternoon MLCAPE approaching 2500-3000 j/kg. Some 
enhancement to midlevel flow (30-40 kt) is expected with the 
approach of a vorticity lobe rotating around the southeastern 
periphery of the NE closed low, which will favor organized 
multicells and some supercell structures as convection develops 
southward in advance of the diffuse wind shift across MO. Some 
clustering of the storms will be possible across east central and 
southeast MO, where the damaging wind probabilities have been 

..southern Appalachians into the Carolinas this 
a series of remnant mcvs will move from Kentucky toward Virginia/NC around the 
southwestern periphery of a midlevel trough over New England. 
Surface heating is underway across the Carolinas in the wake of 
overnight convection and along/south of the thicker cloud band and 
slow-moving synoptic front from eastern Kentucky to north central NC. As 
low-level destabilization continues, thunderstorm development is 
expected this afternoon from northeastern Tennessee and southeastern Kentucky 
across western and central NC in the zone of differential heating 
and near the southern fringe of the remnant mcvs now crossing 
southwestern Virginia and KY/TN. Multicell clusters will be the primary 
convective Mode, with the potential for occasional wind damage with 
downbursts through this evening as storms coalesce on outflows and 
move southeastward toward the coast. 

..central OK to southwest MO this afternoon into tonight... 
The remnants of overnight convection linger this morning across 
central OK, though this convection should weaken by midday. Gradual 
thinning of cloud debris and modification of the outflow air mass 
from overnight storms will result in destabilization up to the I-44 
corridor, just southeast of the quasi-stationary front in OK. 
Renewed thunderstorm development will be possible late this 
afternoon continuing into tonight along the boundary, where moderate 
buoyancy and the southern periphery of the stronger mid-upper flow 
will support a mix of multicell clusters and marginal supercells 
capable of producing isolated damaging gusts and large hail. 

..southwest into north central Montana this evening... 
A pronounced midlevel trough and embedded jet streak crossed eastern 
Washington early this morning, while the larger-scale trough will move 
eastward over the northern rockies later today through tonight. 
Low-level moisture is somewhat limited this morning, though strong 
surface heating and residual boundary-layer dewpoints around 50 f 
will support weak surface-based cape this afternoon. Some 
high-based convection is expected to form over the higher terrain of 
southwestern Montana late this afternoon and subsequently spread 
northeastward across west central into north central Montana late this 
evening through early tonight. An increase in midlevel flow and 
inverted-v profiles in the low levels will support a threat for 
isolated strong/damaging outflow winds and marginally severe hail 
for a few hours this evening. 

.Thompson/leitman.. 06/25/2018 


Mesoscale Discussion

acus11 kwns 251630 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 251629 

Mesoscale discussion 0874 
National Weather Service Storm Prediction Center Norman OK 
1129 am CDT Mon Jun 25 2018 

Areas affected...the Great Smoky Mountains and western Carolina 

Concerning...severe potential...watch possible 

Valid 251629z - 251730z 

Probability of watch issuance...60 percent 

Summary...isolated gusts of 45-55 mph and locally up to around 60 
mph appear increasingly likely this afternoon. Pockets of wind 
damage are expected. 

Discussion...an mesoscale convective vortex over central Kentucky will continue east towards the 
Cumberland Gap and southwestern Virginia this afternoon. A belt of 40-45 
kt westerly flow at 1-2 km above ground level from khpx and kohx on the south side 
of the mid-level circulation will move into the Cumberland Gap 
vicinity later this afternoon. Surface temperatures are warming 
into the middle to upper 80s degrees f with additional warming into 
the lower 90s expected. The net result of steep 0-2 km lapse rates 
(7-8 degrees c/km) will support a more favorable environment for 
strong gusts to reach the surface. The preferred multicell Mode 
will limit the overall risk but localized damaging gusts are 

.Smith/Thompson.. 06/25/2018 

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


Latitude...Lon 36558344 36478095 36038028 35178023 34758033 34528056 
34528142 34348312 34808415 35368436 36558344