Water Vapor Showing Jet over Pacific NW US

75-90 knot upper jet from morning raobs over the northwest US.  Shortwave trough moving ashore this afternoon with a small area of divergence moving into western WY.

Western Wyoming Cell Developing

IR imagery showing a taller/colder cell in western Wyoming.  KRIW radar just switched from VCP 35 to 12.  Peak Z aloft now only around 30.  Lightning data, below, shows relatively low FED, but higher TOE, with peak values in the 300's, similar to some of the storms we saw yesterday.



One other thing to note in these, is the relatively low FED and number of ENTLN/NLDN flashes.  That doesn't mesh with the brightness of the TOE.

Charley

Derived Products Comparison

Merged TPW, image above showing an area of higher TPW, 0.5-0.6 in PIH's area, with values of 0.25-0.4 more over RIW.  AllSky product shows a little more variation, with a drier airmass, 0.15-0.25 inches moistening up over the course of a few hours, over the western border to 0.5".  Also seeing those values in the far eastern part of RIW's area.



Total Totals are ramping up over time in the AllSky product, from around 40 to a more severe 55. LI's also are going negative.  K index also going for some storm activity, getting to the mid 30s.  CAPE's are higher over PIH, but likewise rising across the region...with a similar max in the eastern RIW area.

Charley

Storms tracking toward St. Louis

A line of storms is north of St. Louis as of 630 pm CDT and is tracking southward toward an area of increased CAPE per All Sky LAP product.  This convection continues to trigger along the leading outflow.  The overall environment has limited shear so it is primarily cold pool driven.  ProbWind has consistently displayed around 65-78% since around 600 pm CDT.

Merger of storms

SPC issued a meso discussion talking about the threat for severe wind gusts on cells bowing out towards St. Louis.  The cell in Pike county on the look above has the outflow boundary tied into it on this RGB (in blue) and the updraft still is stronger with waves radiating out from the overshooting top.  We decided to issue a large SVR for winds traveling southeast out of this storm.

TPW in a convective environment

Below is a comparison of two different TPW products (AllSkyLAP layer Precipitable water and Merged TPW Composite Sat Sfc Merged Total Precipitation Water) compared to RAP Analysis from the SPC Mesoanalyst page.

Control group: SPC Mesoanalysis Precipitable Water

The AllSkyLAP product (below) seems to do a better job at "painting the picture," however, it's reliance on the GFS model often leads to a delay in PWAT drops in areas of convection. This is highlighted the best across central IL, where RAP Analysis shows PWATs in the 1 - 1.25 inch range while the AllSkyLAP product shows values closer to the 1.5 inch range straight from GFS output.

AllSkyLAP

TPW (below) does a better job at accounting for this, at least across the central IL study area, resulting in more realistic 1.1 to 1.3 inch values.

TPW

ILX Mesoscale Discussion

GOES_East Mesosector 2 Imagery (Band 2)

The effective surface cold front remains well north of Illinois, draped west to east across central Wisconsin as of the 22z surface analysis. Further south across the state, two main forcing mechanisms continue to play host to strong to severe convection. The first (southernmost boundary) is nearly stationary acting as the area of primary convergence, while also service as the dividing line between 70 degree dewpoints (south) and mid to upper 60s (north). The second is an outflow boundary loosely associated with earlier day convection, which continues to race southward driven largely by cold pool propagation. This boundary is anticipated to overtake the primary boundary over the next few hours, ushering the majority of shower and storm activity south of the Lincoln IL CWA later this evening (Showcased well by NUCAPS forecasts). With ample CAPE (1500 - 2500 J/KG per the 22z AllSkyLAP product) remaining along and south of said boundaries, storms are expected to retain their intensities through the early evening hours. Primary threats will remain damaging wind gusts, large hail, and flash flooding primarily in areas that see repeat thunderstorm convection this afternoon and evening.

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

Lots of lightning in northwest CWA

Highest FED and bright TOE...



...for the cell in Monroe County MO.  Cell is not that tall however, and ProbSevere is not too excited about it yet.

Charley

Line Running Into Drier Air?

IR and RGB imagery showing outflow coming out of the storms in the eastern LSX area not firing up additional storms.  NUCAPS 400-200 mb RH product shows quite a bit of drier air that the line is pushing into.  More moisture is west of the MO/IL line, so that part of the line may have a better chance to maintain themselves/develop new cores ahead of the line along that outflow.

Charley

Mesoscale Update

Band of storms dropping in from the north is moving into an environment favorable to at least maintain severe wind gusts as well as some hail potential.  AllSky CAPE parameter shows the line moving into airmass with 2500 J/kg, similar to values given by earlier ILX special sounding and recent modified NUCAPS sounding.  Latest RAP shows DCAPEs up to 1400 J/kg, indicating good potential for severe wind gusts. Had a couple of reports of blackout conditions from blowing field dirt along I-55 near Litchfield.

Charley