SVR issued more because of previous reports

Had separate reports of 51 and 58 mph from earlier storms in the area.  ProbSevere wasn't very high in those cells, and neither was the lightning FED.  Given a high DCAPE environment, decided to pull the trigger a little earlier on some of the stronger cells going up.

Charley

All Sky LAP CAPE Too High?

Just prior to 20z the All Sky LAP CAPE shows 1000-1200 J/kg of CAPE across eastern ID.  However, most of this is in a cloudy or GFS layer depiction.  Looking at the GOES 16 derived CAPE, it only shows a narrow region a calculated data in eastern, ID that is about half (500-600 J/kg) of what is shown by the All Sky LAP.

All Sky LAP CAPE.

GOES 16 CAPE.

ProbSevere Seems to Handle Splitting Cells

Across the EWX CWA, we've had a number of splitting cells. The gif below includes 0.5 reflectivity with MESH & ProbSevere overlaid. As the cell begins to widen north-south, both MESH and the ProbSevere polygon elongate and split.

Convective Threat for Eastern, ID

The day convection RGB depicts stronger updrafts moving from northern UT to southern ID as of about 2030z.  This area is under a severe thunderstorm watch with no warnings in effect at this time.

Day Convection RGB loop.

Cell Near Twin Bridges, MT, still not severe, though growing

IR shows that cell as having the coldest cloud top.  Donovan heights are around 20 kft for 50dbz to get 1" hail.  This cell is near it, but ProbSevere is not too excited about it just yet.  MESH is under dime-sized and thus ProbHail is 7% now.  Will monitor for further development.  Issuing SPS for pea sized hail now.

Pocatello Storms

We're currently monitoring conditions in eastern Idaho. Right now I'm using various applications to analyze and initialize current conditions. Currently AllSky is showing cape around 1000kj, and PWATS around .80 inches.



That PWAT value on the morning sounding just west of the area was close to .64". Seeing how moisture levels are lower to west I can interpolate that the moisture values are similar to what's show on allsky. The allsky 900-700mb also seems to pick up on the relatively moist area in the lower half of the atmosphere.



Looking downstream we're noticing a line of developing convection using the Day land cloud RGB. It's helpful to analyze just how high the tops of the storms are getting combined with cloud tops.
Zooming in closer I can examine the few storms that have popped up more closely. The RBG help the differentiate between the ambient cirrus clouds from the growing storms. That might not have been as easy to see using a typical visible view.



The AFA and Minimum flash area maximums are hinting at growing convection just downwind. That growth leads to me to anticipate further growth as these storms move into a more favorable environment in eastern Idaho.

EWX Mesoscale Discussion

AllSky_LAP ML CAPE Forecast as of 1930z

19z Surface analysis shows the nearly stationary effective dryline boundary draped SW to NE across the CWA from roughly Del Rio through Briggs, TX. This boundary continues to play epicenter for semi-discrete super-cellular development this afternoon, with additional cold pool driven activity likely to form over the next few hours, especially as a back door cold front begins to slide southward through south-central TX. Latest AllSkyLAP CAPE analysis shows destabilization continues southeast of the dryline, with ML CAPE values nearing 3000 J/KG in and around San Antonio as of 19z. TPW values also remain relatively high southeast of the boundary, with 1.5 to 1.75 inch readings common place. Mid to upper-level kinematics remain favorable for some supercellular structures, so we'll continue to  keep large hail, damaging winds, and an isolated tornado threat in the forecast. Best chance for seeing a tornado (even with relatively week 0-1km shear values) will likely be through 7pm tonight in a cells that can remain discrete for awhile. Flash flooding concerns will continue thanks to the abnormally high PWAT values, especially in areas that see several rounds of convection this afternoon and evening.

----------------------------------------------------------------------------------------------------Mountain Bone

Lightning over the Mountains

Having the different lightning products from GLM as well as data from ENTLN allows you to pick out which cells have started producing lightning.  One flash up in northern WY on this image, the dot in the upper left, did show up in the FED data a couple minutes later.

Charley

Modified Sounding for RIW

Modified the RIW 12Z sounding for low 70s over around 40 in the southwest WY area, and got an MUCAPE of 655 over  A little higher than what AllSky is showing there...


...around 200 in the image above.

Charley

ProbSevere Values Affected by Shape/Size of Polygon

The following series of images shows the change in ProbHail/ProbWind values based on the size/shape of the polygon area. Initially, at 1806Z, ProbSevere was targeting the stronger cell to the south, indicating Hail/Wind 78%/85%. (At this point V was indicating around 20kt). At 1818Z, the northern cell intensified and ProbSevere grouped the two cells together, as a result, Hail/Wind both fell to 42%/61%. At 1827Z, after the southern cell split, the ProbSevere polygone became more filled with deep convection, thus Hail/Wind values increased to 59%/71%. Soon after, around 1834Z, ProbSevere polygons split and then indicated increased probs on the southern cell back to 69%/75% (Hail/Wind).

Incidentally, the larger the polygon, it becomes increasingly likely that ProbSevere values will decrease.