Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 251009

Area Forecast Discussion
National Weather Service Tucson AZ
309 AM MST Sun Jun 25 2017

.SYNOPSIS...Very hot temperatures will continue today, but the
end is near for this historic heat wave. An ongoing moisture
increase will bring an increase in shower and thunderstorm chances
today and Monday. Some drying will limit thunderstorms the second
half of the week, with temperatures closer to normal for late
June as we back away from the record heat.


.DISCUSSION...Multiple strong thunderstorm outflows last night
carried smoke from the wildfires in eastern areas westward into
Metro Tucson and beyond. A nice moisture increase with surface
dew points in the 50s this morning and GOES precipitable water
estimates between 1 and 1.2 inches. The last day of the oppressive
ridge through the desert southwest bringing excessive heat will
be tempered a little by the moisture increase, especially in
eastern areas. With the moisture increase, we`re also expecting a
more active thunderstorm day with the main concern again being
strong, sometimes damaging outflow winds, as well as dry lightning
potential. Some of these storms will drop brief heavy rain, but
with a moisture profile like this, we aren`t expecting widespread
significant rainfall.

As the ridge weakens and shifts south to southwest of our area, a
drier westerly flow will start to push some of the moisture back
out of our area this week. The near record height and thickness
values we`ve been seeing over the past week will recede closer to
normal levels. As this happens, temperatures will do the same,
and our chance of thunderstorms will diminish considerably by
Wednesday or Thursday.

Tropical Depression 4E just turned into Dora south of Mexico. Over
the next several days she should drift slowly northwest to a
position just southwest of the tip of Baja around mid week. No
direct impacts for us, but it will probably help prime west
central to northwest Mexico with deeper moisture. It could even
contribute to moderate surge activity the second half of next
week. We need to build up the deeper moisture south of us before
we can really kick things off and trade the dry microbursts for
wet in early July.


.AVIATION...Valid thru 26/12Z.
SCT-BKN clouds at 8k-15k ft AGL thru the forecast period, though
occasional OVC skies can`t be ruled out E of KTUS. Isolated-
scattered SHRA/TSRA from KTUS/KOLS eastward this afternoon and
evening. SFC wind ELY at 8-12 kts this morning, though stronger
speeds of 15-20 kts are possible near KSAD. Wind becoming WLY/NWLY
this afternoon at less than 12 kts. A few of the stronger SHRA/TSRA
may produce wind gusts to 40 kts and brief MVFR conditions. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Scattered thunderstorms generally from Tucson
eastward and southward through Tuesday. Expect decreasing coverage
of thunderstorms Wednesday, with isolated to scattered thunderstorms
mainly east to south of Tucson. Precipitation will be confined to
near the Mexico border on Thursday and Friday. A slight increase in
moisture will then increase thunderstorm coverage northward next

Morning southeasterly winds and afternoon northwesterly winds will
be periodically gusty through the Gila River Valley again today.
Additionally, any convection which develops will be capable of
producing gusty outflow winds in excess of 40 mph. Otherwise, 20-
foot winds will then exhibit diurnal trends with speeds mainly less
than 15 mph, although some elevated afternoon gusts may occur due to
strong daytime heating.


Excessive Heat Warning until 7 PM MST this evening for

Heat Advisory until 7 PM MST this evening for AZZ514.




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