U.S. Severe Weather Forecast (Convective Outlook)

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000 
acus01 kwns 251301 
swody1 
Storm Prediction Center ac 251300 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0800 am CDT sun Jun 25 2017 


Valid 251300z - 261200z 


..there is an enhanced risk of severe thunderstorms over parts of 
east-central New Mexico... 


..there is a slight risk of severe thunderstorms surrounding the 
enhanced risk and extending to parts of west-central/southwestern 
New Mexico... 


..there is a marginal risk of severe thunderstorms elsewhere from 
south-central Colorado to the Llano Estacado of Texas...and 
borderlands of far West Texas and southern New Mexico... 


... 
Severe thunderstorms with damaging wind and isolated large hail are 
expected across parts of central and eastern New Mexico this 
afternoon and evening. Isolated severe storms are possible 
elsewhere from southern Colorado to southern New Mexico and far West 
Texas. 


... 
The upper-air pattern will be dominated by: 
1. Mean troughing and broadly cyclonic flow over much of the 
central and eastern U.S., And 
2. A persistent high over southern Arizona/northern Sonora region. 
Associated synoptic ridging will move eastward across the northwest 
and Great Basin as substantial shortwave perturbations over the 
Pacific move onshore in western Canada, and approach the California coast, 
late in the period. A weak shortwave trough, close to the center of 
the mid/upper anticyclone, was evident in moisture-channel imagery 
over portions of central and western Arizona. This feature should pivot 
northeastward then southeastward today into western and perhaps 
central nm, as it becomes entrained in the northwest flow aloft 
associated with the eastern U.S. Mean trough. 


At the surface, a complex area of low pressure was analyzed at 11z 
from the St. Lawrence Valley of southern qc to Georgian Bay, with an 
occluded front arching southeastward to a triple point near NYC. A 
cold front was drawn from there southwestward across southeastern 
VA, central SC, southwestern Alabama and southeast TX, becoming a 
quasistationary front over central/northwest Texas. This front became 
ill-defined amidst outflow from an area of scattered to widely 
scattered thunderstorms across much of the Texas Panhandle and 
adjoining extreme eastern areas of nm. The aggregate outflow 
boundary from that convection is acting as the effective frontal 
zone between tcc-cqc in eastern nm, and should become 
quasistationary in a northwest-southeast alignment today from the southernmost 
Sangre de Cristos southeastward through the area between CVS-row. 


..nm, southern co, West Texas... 
In general, scattered thunderstorms are expected to develop in the 
higher elevations of south-central Colorado and northern/central/western 
nm this afternoon, as heating of high terrain removes already-weak 
mlcinh. Activity is expected to assume a mix of multicell and 
supercell modes early, with large hail and damaging gusts likely. A 
tornado cannot be ruled out, though this threat is very conditional 
on storm Mode, timing/character of storm/boundary interactions, and 
storm-scale modulations to ambient kinematic fields. With time 
through the afternoon, activity should move generally southeastward 
across central, eastern and perhaps southern nm, coalescing into one 
or two dominant storm clusters or mcss. Accordingly, the main 
threat should evolve to damaging wind, with isolated large hail 
possible. The easternmost of this convection may reach parts of 
West Texas tonight before diminishing with the loss of inflow-layer 
instability. 


With the outflow-enhanced baroclinic zone expected to stall southeast-northwest 
across eastern nm today, a corresponding instability gradient and 
related corridor of enhanced low-level lift, vorticity, moisture, 
deep shear, and storm-relative boundary-layer flow should set up and 
focus severe potential, including a most-favored corridor for 
potential forward propagation and merging convection. Multiple 
short-fused synoptic-scale (i.E., Rap and parallel rap) as well as 
convection-allowing models reasonably depict this scenario in recent 
runs -- both in terms of explicit convection and fields of 
environmental parameters. Forecast soundings along and near the 
boundary show weak (generally 10 kt or less) surface flow but strong 
directional shear in low levels, beneath about 30 kt of northwest 
flow around 500 mb, contributing to effective-shear magnitudes 40-45 
kt. Strong heating near and south of the boundary, along with moist 
advection and favorable midlevel lapse rates, will contribute to 
MLCAPE exceeding 2000 j/kg over much of eastern nm, with well-mixed 
subcloud layers supporting wind potential. Even deeper mixing, 
beneath weaker but still supportive buoyancy, is expected into the 
central/southern nm mountains and valleys, in support of some 
organized wind potential there as well. The 15% outlook therefore 
has been extended somewhat southwestward. 


.Edwards/picca.. 06/25/2017 


$$ 

Mesoscale Discussion


000 
acus11 kwns 241943 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 241942 
coz000-nmz000-242215- 


Mesoscale discussion 1147 
National Weather Service Storm Prediction Center Norman OK 
0242 PM CDT Sat Jun 24 2017 


Areas affected...portions of nm and far south-central Colorado 


Concerning...severe potential...watch unlikely 


Valid 241942z - 242215z 


Probability of watch issuance...20 percent 


Summary...an isolated threat for large hail and strong to locally 
damaging winds should persist through early evening. Watch issuance 
is unlikely. 


Discussion...beneath upper ridging centered over northern Mexico and 
the southwest, persistent weak low-level easterly flow across nm and 
south-central Colorado is encouraging initially isolated convective 
development across west-central nm. Additional thunderstorms are 
expected to develop across nm this afternoon aided by terrain-driven 
circulations. Visible satellite imagery shows almost total clearing 
along and west of the Central Mountain chain of nm, and temperatures 
have warmed into the 80s and lower 90s across lower terrain. Modest 
low-level moisture characterized by upper 40s to lower 50s dewpoints 
is present across this region, and combined with steep mid-level 
lapse rates and diurnal heating, MLCAPE generally ranging 500-1000 
j/kg has developed. Although mid-level northwesterly winds weaken 
with southern extent across nm, there is sufficient mid-level flow 
to support mainly 30-35 kt of effective bulk shear. This should be 
sufficient to weakly organize thunderstorm updrafts, and isolated 
instances of large hail and strong to locally damaging winds may 
occur with any thunderstorms across this region through the 
remainder of the afternoon and continuing into the early evening. 
There may be some potential for loosely organized convective 
clusters to develop and move southeastward across western/central 
nm, perhaps posing a slightly greater wind threat with time. 
Regardless, the overall severe threat will likely remain too 
isolated to warrant watch issuance due to the marginal 
thermodynamic/kinematic environment. 


.Gleason/guyer.. 06/24/2017 


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


Attention...WFO...pub...abq...epz... 


Latitude...Lon 33790887 34940870 35480805 37610505 37470418 36520402 
35140449 32910558 31840710 31820819 31510824 31560899 
33790887