Area Forecast Discussion
Issued by NWS Tucson, AZ

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524
FXUS65 KTWC 250417
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
915 PM MST SAT SEP 24 2016

.SYNOPSIS...A low pressure system south of the area will bring
scattered showers and isolated thunderstorms Monday into Tuesday.
Gusty east winds will also accompany this system. A chance of
showers and thunderstorms continues Wednesday and Thursday mainly
east of Tucson, then a drying trend will occur by next weekend.

&&

.DISCUSSION...A few showers and thunderstorms managed to develop
this afternoon in the far southeast corner of Arizona around
Douglas. This activity had since dissipated with debris cloudiness
shifting out of area late this evening. Otherwise, mostly clear
skies with temperatures similar to readings on Friday evening. At
any rate, the current forecast looked in good shape so no updates
necessary.

&&

.AVIATION...Valid through 26/06Z.
SCT-BKN clouds at 8-12k ft AGL near KDUG through 25/09Z. Sfc winds
around 10 kts becoming light and terrain driven overnight. FEW-SCT
clouds at 8-12k ft AGL Sunday afternoon generally near the NM and
Int`l borders with a slight chance of -SHRA/-TSRA. ELY sfc wind
increasing to around 8-12 kts late Sunday morning into the
afternoon. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Mainly light westerly/northwesterly winds will
continue into this evening with easterly breezes around 15-20 mph
developing Sunday afternoon and persisting into Tuesday. Moisture
will rebound back into the area Sunday evening as an upper level low
begins to affect Arizona. This will result in a chance of showers
and thunderstorms through midweek followed by drier conditions by
next weekend.

&&

.PREV DISCUSSION...the 24/12Z GFS/ECMWF/CMC were quite similar with
developing an upper low over northeastern Sonora Mexico around
midday Sunday. This upper low is then progged to move southwestward
to near the Baja California spur by midday Monday. Various hi-res
models were similar with maintaining precip-free conditions across
this forecast area Sunday. However, for this forecast issuance, have
maintained a slight chance of showers/tstms Sunday afternoon mainly
near the International border adjacent Santa Cruz/Cochise Counties,
and across the White Mountains.

Moisture should increase from southeast-to-northwest Sunday night
into Monday in response to a deep ely/sely flow regime. Precip
chances should also increase correspondingly, and have opted for a
chance of showers with isolated thunderstorms for most sections by
Monday afternoon. The various NWP models depict the bulk of deeper
moisture Tuesday to be well north of the area. The coverage of
showers/tstms is expected to be less Tuesday versus Monday, and have
continued with a slight chance of showers and isolated thunderstorms
area-wide Tuesday.

The upper low is progged to move northward Tuesday night into far
southeast California/southwest Arizona, then weaken and continue
northward into northwest Arizona Wednesday. The flow aloft is also
progged to become increasingly southwesterly Wednesday. This flow
regime in combination with lingering moisture may ultimately produce
the possibility of more-conventional severe weather Wednesday
afternoon/evening. Still much too soon for this kind of detail to be
definitively determined.

At any rate, the best chance of showers/tstms Wed-Thur should be
across eastern sections. Thereafter, increasingly swly/wly flow
aloft Fri-Sat will likely shunt deeper moisture well east of the
area. Moisture at this time appears to be adequate to support a
slight chance of showers/tstms Fri-Sat mainly near the New Mexico
border.

&&

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

&&

$$

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