Forecasters: Jay Miller (NCAR/MMM) and NWS
Today:
The ridge and monsoon flow continue with some embedded convective systems moving northward out of New Mexico and into Colorado. Ample moisture remains in the STEPS domain, with dewpoints in the mid-60s. A weak system passed through the STEPS area leaving us overcast this morning. Flow aloft is still too weak for significant shear that could produce long-lived, severe storms.
Some convective cells may occur, and they should be short-lived but could become severe. Significant convection is expected over the front range but this will likely not make it into the STEPS domain. Northeast Colorado is an area that is prime for more severe convection and heavy rainfall.
Note: The 9am formal weather briefing and debriefing of the previous day's operations have been suspended. We will maintain a daily look at the weather, but no other briefings/debriefings will be conducted. The forecast matrix will no longer be posted.
The following research systems are all operational: the Ops Center, CHILL, S-Pol, LMA, MGLASS, and YRFS. These systems are all that remain available to STEPS. CHILL will remain available for coordinated scans through Friday, July 14. S-Pol will continue through Sunday, July 16, mostly for Charlie Knight's young cloud studies, but will be available to scan storms in the LMA 2D/3D lightning mapping area should they develop +CGs. The MGLASS unit has been directed to take routine soundings at 18Z at Goodland for Wednesday (July 12) through Friday (July 14). Friday will end MGLASS' participation in STEPS since all sondes will have been expended, except maybe one or two.
Both radars have been put in a very loose standby in the event that significant and worthwhile convective storms develop in the research Doppler lobes. MGLASS soundings will be taken at Goodland at 18 and 21Z. Miller has returned to Boulder where he will monitor any weather which might develop and provide broad guidance should coordinated radar scans be warranted. CHILL will run a sequence of surveillance scans at a few elevation angles every 15 min to help monitor local weather conditions.
The general expectation as of late morning was that the most likely form of intense convection would be scattered, slow moving, pulse-type storms. Such a situation would not require particularly intensive research radar surveillance to be maintained. However, by noon morning clouds had cleared in the immediate CHILL area, and surface heating increased appreciably. Partially in response to this, a severe thunderstorm watch was issued for most of NE Colorado. An isolated storm developed approximately 50 km SW of CHILL and drifted north-northwestward into the western dual Doppler lobe. It did not produce a significant amount of lightning and it generally weakened as it entered the western dual-Doppler lobe. Ultimately, CHILL and S-POL began the 2 minute RHI and 4 minute PPI scan sequence on the storm. As this initial storm faded out completely, attention shifted to a much larger area of convection that was centered over Morgan County CO (out of first trip range from both research radars). WSR-88D data showed several intense, quasi-stationary storms in this area which were variously responsible for reports of hail, flooding rains and a couple of tornadoes. The NLDN display showed considerable +CG activity from these echoes. Around 1815 MDT coordinated scanning of this area began in the hopes that the southern end of the convective area would move into the western lobe. By 1900 it was apparent that any echoes drifting towards the western lobe were weakening. Operations were ended with the concurrence of the LMA group and GLD WSFO.