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Day 1 Outlook Convective Tornado
Hail Wind
Categorical Day1 1630Z Outlook
  
Images courtesy of the NWS Storm Prediction Center
 Forecast Discussion

  
000
ACUS01 KWNS 251605
SWODY1
SPC AC 251604

Day 1 Convective Outlook  
NWS 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 IA INTO MO...AND FROM THE SOUTHERN
APPALACHIANS ACROSS PARTS OF THE CAROLINAS...

...SUMMARY...
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 KS border will
drift generally eastward toward IA/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 KS 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 IA.

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 MCV moving
eastward over the lower OH 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
increased.

...Southern Appalachians into the Carolinas this
afternoon/evening...
A series of remnant MCVs will move from KY toward VA/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 KY to north central NC.  As
low-level destabilization continues, thunderstorm development is
expected this afternoon from northeastern TN and southeastern KY
across western and central NC in the zone of differential heating
and near the southern fringe of the remnant MCVs now crossing
southwestern VA 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 MT this evening...
A pronounced midlevel trough and embedded jet streak crossed eastern
WA 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 MT late this afternoon and subsequently spread
northeastward across west central into north central MT 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

$$