U.S. Severe Weather Forecast (Convective Outlook)

Idag
Imorgon
Day Three

000 
acus01 kwns 192000 
swody1 
Storm Prediction Center ac 191959 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0259 PM CDT Tue Jun 19 2018 


Valid 192000z - 201200z 


..there is an enhanced risk of severe thunderstorms across parts of 
the Central Plains... 


..there is a slight risk of severe thunderstorms outside of the 
enhanced risk area in the Central Plains and in the mid-Atlantic... 


... 
Severe thunderstorms are expected across the Central Plains this 
afternoon and evening, while marginally severe thunderstorms are 
expected from the Midwest into the mid Atlantic region. 


... 
Several changes have been made to the outlook for this issuance. The 
first change is to add a 10 percent tornado probability in parts of 
northeastern Colorado. A tornadic supercell is ongoing to the 
northeast of the Denver Metro area. This storm is part of a cluster 
of storms that are expected to maintain a severe threat and move 
eastward across northeast Colorado over the next few hours. The 
storms should have potential to produce more tornadoes through early 
evening. The second change is to expand the enhanced risk area 
including the 30 percent and significant hail contours northwestward 
across northeastern Colorado where several severe hail storms are 
ongoing. This activity is forecast to move eastward across the 
remainder of northeastern Colorado and into western Kansas/southern 
Nebraska later this evening. The final change to this outlook is to 
trim the northern edge of the slight risk area in the mid-Atlantic 
region behind a cold front that is moving southward into northern 
Virginia. 


.Broyles.. 06/19/2018 


Previous discussion... /issued 1129 am CDT Tue Jun 19 2018/ 


..Central Plains... 
Upper low over the northern rockies is forecast to move eastward and 
open into a short-wave trough as stronger winds on the southern 
periphery of the low translate eastward into the Central Plains 
through tonight. Water vapor imagery indicates a speed maxima 
moving eastward across southern Utah at this time, and this feature 
is expected to move into the Central High plains by late 
afternoon/evening, enhancing large scale ascent over the area. 


A surface low over southeast Colorado is expected to move slowly 
eastward with a frontal boundary extending across western Kansas 
into southeast Nebraska. This will maintain an easterly component 
to the low-level winds into the plains of southeast Wyoming and most 
of eastern Colorado with ample moisture continuing north of the 
boundary. Visible imagery shows limited clouds over much of eastern 
Colorado, western Kansas into southwest Nebraska which will permit 
stronger diabatic heating to occur this afternoon. With moderately 
steep mid-level lapse rates in place, the environment will become 
moderately unstable with MLCAPE values reaching 1500-2500 j/kg this 
afternoon. 


Several clusters of storms are expected to develop over parts of 
eastern Colorado, southeast Wyoming and western Kansas during the 
mid-late afternoon as heating combined with approaching large scale 
ascent aloft and upslope flow weaken the cap. Wind profiles will 
exhibit strong directional shear with height with effective shear of 
40-50 kt which will enhance storm organization and intensity. A few 
supercell storms are likely to develop and spread eastward, 
especially over parts of eastern Colorado into far western Kansas 
and southwest Nebraska. These will pose a threat for very large 
hail, damaging wind gusts, and possible tornadoes during the late 
afternoon and early evening. 12z cam/href guidance indicates 
potential for storms to grow upscale into one or two eastward moving 
linear mcss this evening with damaging winds becoming the greater 
threat. Activity will continue to progress eastward into the 
overnight hours with a gradual weakening trend developing by 03-06z. 


..southern Maryland and northern Virginia area... 
Despite warm mid-level temperatures, strong diabatic heating of a 
very moist low-level air mass is resulting in moderate instability 
with MLCAPE of 1500-2000 j/kg. Storms are forming along a southward 
moving cold front that will move into the area this afternoon, with 
additional storms expected to develop over the mountains and move 
east-southeastward. Sufficient west-northwest winds above the 
surface coupled with low-level inverted-v soundings and large dcape 
values indicate potential for damaging wind gusts to occur with 
stronger cells this afternoon and evening. See Maryland 789 for 
additional short-term details. 


..middle Mississippi Valley to the upper Ohio Valley... 
A very warm and moist low-level air mass remains in place along and 
south of a front that extends across the region. Weak winds aloft 
and limited vertical shear indicate potential for weakly organized 
and pulse storm characteristics, however, continued low-level 
heating will result in moderate instability with MLCAPE of 1500-2000 
j/kg. Potential will exist for a few wet microbursts to develop as 
storms continue to develop from Missouri into the upper Ohio Valley 
region this afternoon but uncertainty regarding overall storm 
organization will preclude introduction of higher wind probability 
values at this time. 


$$ 

Mesoscale Discussion


000 
acus11 kwns 191955 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 191954 
nez000-ksz000-coz000-nmz000-wyz000-192200- 


Mesoscale discussion 0793 
National Weather Service Storm Prediction Center Norman OK 
0254 PM CDT Tue Jun 19 2018 


Areas affected...eastern Colorado 


Concerning...Tornado Watch 191... 


Valid 191954z - 192200z 


The severe weather threat for Tornado Watch 191 continues. 


Summary...severe weather threat continues across Tornado Watch 191. 


Discussion...severe and tornado warned storms continue across the 
northern half of the watch. The storms have strengthened into 
supercells and should remain discrete in the coming hours. 
Three-inch hail has already been reported in Arapahoe County, and 
the severe hail/wind and tornado risk will continue into this 
evening. Latest hrrr/rap guidance indicates the storms will 
eventually merge and form a mesoscale convective system this evening across far eastern 
Colorado, western Kansas, and southwestern Nebraska. Some storms 
could redevelop behind these initial storms along the northern Front 
Range. 


Farther south, the cumulus field has struggled to build, but 
confidence remains that a discrete storm or two will form along the 
southern Front Range and move eastward. There is good potential for 
these storms to develop into discrete supercells capable of 
producing large hail, damaging winds, and a tornado. Additionally, a 
new storm has just formed in far southeast Colorado near the surface 
front. 


.Nauslar/Peters.. 06/19/2018 


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


Attention...WFO...lbf...ddc...gld...pub...bou...cys...abq... 


Latitude...Lon 41010620 40410575 39950567 39870538 39230540 38810532 
38630515 38050506 37890553 37630550 37600524 37260518 
36960499 37010203 40990203 40970536 41010620