Light Shower Here

Hazy, dirty skies this morning at 7:20 am MST.

There were scattered thunderstorms around southeast Arizona yesterday afternoon and evening, and then some light showers around parts of metro during early morning hours. Rainfall for 24-hours ending at 7:00 am this morning shown here: above from ALERT network where 17 sites recorded 0.04" or more and below from MesoWest which shows quite a few reports of light amounts or a Trace across much of metro area. We had 0.01" here at a bit after 3:00 am. Plot of detected CG flashes (second below - from Atmo and Vaisala) shows a distinct lack of flashes across a significant portion of the metro area.

The morning 500 mb analysis (above) shows weak height gradienst and a chaotic anticyclone across southern portion of contry - one weak anticyclone center appears to be off to our southeast in northern Mexico. The morning sounding has increased moisture below 600 mb and some CAPE, with continued light/variable winds aloft. The sounding appears more favorable to me for lower elevation storms today. However, the 12 UTC WRF-RR forecast for rainfall through midnight tonight indicates little shower activity for Pima County - time will tell.

Down Day Yesterday

Touch of pink over the Catalinas at about 5:15 am MST, just before sunrise.

Scattered thunderstorms occurred across the western two thirds of Pima County yesterday, but totally avoided the Tucson area (plot of detected CG flashes above from Atmo and Vaisala for 24 hours ending at 0803 UTC this morning). Was definitely a down day, as predicted by the WRF-RR (see post below). Across the entire ALERT network there were only three reports of rainfall - below ending at 7:00 am this morning.

There was no morning sounding from TWC today. Above shows sounding forecast for 4:00 pm this afternoon by the 12 UTC run of the WRF-RR at Atmo. The sounding has a very deep and relatively dry boundary layer (BL), a sliver of CAPE, and light/variable winds through the troposphere - not very promising.

However, the model forecasts storms in eastern Pima County, as per composite radar echoes below valid at 5:30 pm. Precipitation forecast from the same run (second below) indicates scattered light rainfall across the metro area, with a strong cell apparently hitting the airport - note the 0.40" there. So, hopefully a bit more active day - I'll watch to see what transpires.

Few Showers Around

Some cloud color over the Catalinas before sunrise this morning.

There was very limited thunderstorm activity over Pima County yesterday - plot above shows detected CG flashes for 24-hours ending at 12 UTC this morning. The airport did report thunder during the mid-afternoon, as well as 0.04" of rain. Nothing here.

The Alert network sites (below for north and south portions) indicated scattered, mostly light amounts over the mountains and southern portion.

Yet another morning sounding with limited moisture below 700 mb (above), some CAPE, and mostly light and variable winds aloft. We really need a feature that will move some low-level moisture up the GoC - as per: an MCS into the middle GoC, a TS near the south end of Baja, or an inverted trough (IT) moving west across northern Mexico.

The forecast for precipitation through midnight tonight (below, from 12 UTC WRF-RR) looks very dismal.

Rain In The Gauge!

Heavy clouds over the metro area this morning, and perhaps a few lingering sprinkles around.

Plot of detected CG flashes for 24-hours ending at 1203 UTC this morning (from Atmo and Vaisala) shows that thunderstorms mostly avoided eastern Pima County during the period.

However, light showers crossed our area during the early morning hours today. The ALERT reports (above and below), indicate that amounts of 0.04" and greater mostly avoided the metro area. But amounts were heavy over the Catalinas - one site reported over two inches.

Plot focused on the metro area (second below, from MesoWest) shows that many spots in the city had light amounts, or a Trace. We had 0.06" around 3:30 am MST this morning - just enough to dampen the soil.

Morning sounding from TWC/TUS (above) shows that PW jumped to over an inch and a half - but, it will be hard for limited heating today to break the strong inversion at 850 mb. Winds were light and variable through most of the troposphere.

Forecast 500 mb level from the 06 UTC GFS (above) shows a weak trough stretcheing from northeastern New Mexico to southeastern Arizona. Anticyclone centers are over Nevada and central Texas - note that TS Celia is well west of southern end of Baja - that storm is moving west and weakening. 

The 12 UTC forecast (below) from the 12 UTC WRF-RR run at Atmo indicates little activity today for all of Pima County, with perhaps some showers on the Catalinas. After a very active day for most of Arizona yesterday (see CG plot above), model forecast indicates much less storm activity today.

Increased Showers Today

Mostly middle clouds overhead this morning.

Plot of detected CG flashes (above - from Atmo and Vaisala) is for 24-hours ending at 0830 UTC this early morning. Very little thunderstorm activity across all of southeastern Arizona yesterday, as main activity was in a band from Sonora northward across western Arizona. There were a couple of severe wind reports with this band.

Precipitation (below) was extremely limited across the ALERT network with only 9 reports of rainfall, and the entire metro area very suppressed. Still waiting for meaningful rain in my gauge.

The 500 mb pattern (above) remains similar to yesterday, but with weak trough from from near Four Corners to northern Baja that will shift a bit eastward during the day today. The morning TWC sounding (below) is also very similar to yesterday's.

The 12 UTC WRF-RR forecasts a significant increase in storm activity today over eastern Pima and Santa Cruz Counties (radar echoes above forecast for 5:30 pm this afternoon). Rain is also forecast by the model across Tucson Metro, with a tenth of an inch at the airport (below for period ending at midnight tonight).

The NWS morning forecast is shown  second below, with 60 percent POPs indicated for the airport this afternoon.

Down Day Here Yesterday

Heavy cloud cover over metro and Catalinas a bit after sunrise this morning.

Graphic this morning on NWS webpage (above) focuses on lightning safety - a good graphic that I don't recall seeing before. It's important because the two most significant weather hazards here in southeast Arizona are lightning and flash floods.

Plot of detected CG flashes below is for 24-hours ending at 5:03 am MST this morning. Note that storms avoided much of the Tucson area. There was thunder and Trace of rain reported at both the airport and DM (also gust to 38 mph at the AFB). 

ALERT plots (above and below) are for 24-hour rainfall ending at 7:00 am this morning - only 25 scattered sites reported 0.04" or more, with max amounts on the Catalinas.

This morning's 500 mb analysis (above) shows light and variable winds over the Southwest, with the large anticyclone center over southern Arkansas. Band of higher RH at this level covers eastern Arizona and much of New Mexico.

This morning's sounding is much like yesterday's with fairly dry air below 700 mb, little CAPE, and light/variable winds below about 450 mb. The 12 UTC WRF-RR forecast for rainfall through midnight tonight (below) indicates only some spotty light showers for eastern Pima County. Note that yesterday's WRF-RR forecast verified quite well (see previous post).

More Scattered Showers

Heavy storm over the Catalinas yesterday afternoon about 2:30 pm MST.

Plot of detected CG flashes (from Atmo and Vaisala) for 24-hours through 1:30 am this morning - limited activity over Tucson area, but not quite a classic donut hole. Reports from the ALERT network of 24-hour rainfall (two plots below) through 8:00 am this morning indicate limited areal coverage of mostly light showers (four sites with over half an inch). Nothing in the gauge here yet again.

The 500 mb analysis this morning (above - ignore the bad analysis of a closed low to our east) indicates a weak trough from Four Corners region south to end of Baja. The TWC/TUS morning sounding (below) is quite a mess. There are signals of the influence of mesoscale downdrafts, little CAPE, some middle level moisture, and a chopped-up wind profile below 400 mb. I'm hard pressed to find anything good to say, but can hope that there might be some improvements during the day.

Two graphics here from Atmo's WRF runs to look ahead for this afternoon. Forecast above is from the 12 UTC WRF-RR and shows CAPE at 6:00 pm being very small in our area. Forecast below is for rainfall through midnight tonight (from the 06 UTC WRF-GFS - 12 UTC WRF-RR is very similar). So, the models predict another day with widely scattered storms, but not much in the way of significant rainfall.