Special Weather Statement, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
1055 AM MST Sun Aug 4 2019

.SYNOPSIS...After some cloudiness this morning, we will start to
clear out later with isolated showers and thunderstorms this
afternoon and again Monday. Temperatures will remain several
degrees above average to start the week. A more favorable pattern
for storms will bring increasing thunderstorm chances the second
half of the week into the coming weekend.

&&

.DISCUSSION...No new insights this morning based on the latest
models. That said, the current forecast looked on track. Please
refer to the additional sections in this product for more details.

&&

.AVIATION...Valid through 05/18Z.
Expect less activity today compared to yesterday, however the threat
remains for isolated to scattered SHRA/TSRA this afternoon and
evening. The best chance for convection will be KOLS/KDUG. Cloud
decks will start as FEW/SCT and become SCT/BKN around 8-12K FT AGL
by the afternoon and evening. Clouds will thin after sunset. Expect
gusty and erratic winds near any TSRA with local MVFR CIGS and VSBYS
possible. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...The daily cycle of afternoon/evening showers and
thunderstorms will continue through the forecast period. Minimum RH
values remain above 20-25 percent, and overnight recoveries will be
very good. Min RH values will rise in the 25-35 percent range by the
middle of next week with continued very good to excellent RH
recoveries. Even with the abundant moisture, temperatures will be
several degrees above normal this weekend into early next week.
Temperatures may "cool" closer to average by the middle of next
week. Aside from gusty erratic winds from thunderstorm outflows,
wind trends stay light and terrain driven.

&&

.PREV DISCUSSION...Broad high pressure over the desert southwest
will continue to bring temperatures several degrees above average to
start the week. One caveat today is the thunderstorm activity south
of the border this morning with debris cloud spreading slowly into
Southeast Arizona to start the day. This will slow surface heating a
bit, but by late morning we should have some clearing. We again have
enough moisture for a chance of thunderstorms this afternoon and
evening, with surface dew points generally in the 60s and
precipitable water values ranging from around 1.3 inches in eastern
areas to 1.6 west. With the delayed start to surface heating, we may
struggle a bit compared to yesterday. Models also hinting at some
weak NVA this afternoon. This suggests a mountain-hugging storm
environment with less valley action.

Another below average thunderstorm day Monday as we start to lose a
bit of moisture under weak subsidence and only a seep from the Gulf
of California. Temperatures will continue several degrees above
average.

By Wednesday, high pressure will start to elongate a little further
eastward into Texas. This is often a good pattern to engage the Gulf
of Mexico and easterly wave action. Ensembles and deterministic
output don't agree on timing, but just about everything has a couple
of impulses rotating in from the southeast the second half of next
week and/or next weekend. These will provide a more structure for
storms, and the deeper flow will probably initiate a more active
period with a broader moisture influx from the south and east. Our
forecast will reflect this with increased storm coverage and
increased QPF values in general starting Wednesday with a steady
increase into Friday and Saturday. We can fine tune the timing
details with up/down periods as we get closer.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

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