Area Forecast Discussion

SYNOPSIS

Breezy afternoons with temperatures near to just above normal into next week. Increasing moisture is expected through the coming several days with chances for showers and thunderstorms arriving by this weekend.

DISCUSSION

The Greek philosopher Plato once said (or at least it is attributed to him saying), "the beginning is the most important part of the work". That is where we find ourselves as we begin to see the ingredients of the Monsoon take root across Southeast Arizona. Although the actual season doesn't start until Monday June 15th, the upper pattern this afternoon is defined by a trough of low pressure off of the Baja Peninsula and a subtropical high establishing itself across Texas and NRN Mexico. The resulting southerly flow between these two features into our neck of the woods is underway, with the latest GOES precipitable water imagery indicating PWATs between 1.00-1.25 inches spilling into the lower deserts of central/western Pima and Yuma counties. Strong contrast of lower level moisture with surface dewpoints in the lower to mid 50s across western Pima county to the mid 30s in the Tucson Metro Area and near 40 near Nogales in Santa Cruz county.

Despite the moisture, there is a general lack of upper forcing around today to really aid thunderstorms development. I would expect to see a slight chance (10 percent) of a weak storms developing this afternoon along the 300 mb deformation axis which extends from NE Sonora Mexico into SW AZ. Just a little too dry for any measurable rainfall, but in those areas just outside of the deeper moisture (Santa Cruz county into the ERN portions of the Tohono O'odham Nation) we can see some of the weak downdrafts result in some gusty outflows to 30-35 mph and localized blowing dust.

Moisture will continue to make its way into Southeast Arizona over the next few days, with surface dewpoints jumping into the mid 50s to lower 60s Sunday. During this period, we will see weak shortwaves shear off of the upper trough to our west and track across the CWA both Friday and Saturday, with stronger upper forcing/lift moving across Southeast Arizona Sunday and Monday as the larger-scale northern stream trough clips the eastern portions Arizona. This will increase the overall chances for thunderstorms (20-40 percent) into the weekend. Some of these storms can get frisky, with strong outflow winds the main concern.

Otherwise, as the previous AFD mentioned, the forecast high temperatures remain just above normal through much of the forecast period with the subtropical ridge approaching, however temperatures may be impacted by cloud cover with any convective activity that develops.

AVIATION

Valid through 13/00Z. Increasing cloud cover today with FEW-SCT 10-14k feet AGL developing this afternoon and SCT- BKN cirrus clouds at 20k feet AGL. SCT-BKN 9-12k feet clouds will develop Saturday afternoon. Weak mainly dry storms this afternoon from Santa Cruz county into central Pima county may produce localized wind gusts to 30 kts/5SM BLDU. Otherwise, surface winds west/northwest 10-15 kts with gusts to 22 kts through this evening...becoming light and terrain driven less that 10 kts overnight. Stronger winds 15-18 kts with gusts to 30 kts at KSAD both this afternoon and Friday afternoon. Aviation discussion not updated for TAF amendments.

FIRE WEATHER

Winds will remain west/northwest each day into early next week with speeds of 10-15 mph and gusts to 22 mph across much of the area with stronger speeds of 15-20 mph and gusts to 30 mph in lower elevations of Graham county. Moisture will be on the rise through the weekend. Minimum relative humidity 8-14 percent today and 14-20 percent in the mountains, progressively increasing to 15-25 percent in lower elevations and 25-35 percent in the mountains by Saturday. This will bring bring chances for showers and thunderstorms with gusty outflow winds and lightning as early as Friday, with better chances (15-40 percent) this weekend.

TWC WATCHES / WARNINGS / ADVISORIES

None.