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Area Forecast Discussion (AFD)

Issued by NWS Tucson Arizona (TWC)

FXUS65 KTWC 132101

Area Forecast Discussion
National Weather Service Tucson AZ
201 PM MST Fri Sep 13 2019

.SYNOPSIS...Temperatures will warm back above normal today and 
Saturday while increasing moisture will result in a better chances
of showers and thunderstorms this weekend into early next week.
Then a drying trend during the middle of next week. 


.DISCUSSION...Current radar shows isolated to scattered showers
and thunderstorms mainly from I-19 eastward. Moisture is slowly
creeping in with dewpoints in the lower 50's along the
international border and upper 40's elsewhere. Expect these
dewpoints to climb as the day goes on thanks to easterly flow in
the lower to mid levels along with outflow from storms. Storms 
will likely persist into the evening hours mainly east of Tucson. 
The main impact from these storms will be gusty outflow winds with
DCAPE values between 500-1000 J/kg. Hi-res models also have 
outflows moving through southern Pinal County which could trigger 
some patchy blowing dust this evening. Locally heavy rainfall will
also be possible.

Saturday into Sunday deeper moisture will be available and will
penetrate deeper into southern Arizona. Because of this isolated
to scattered precipitation coverage will expand to most of the 
CWA. PWAT values will range from 1.3 to 1.6 inches across the
area. Locally heavy rainfall will be possible each of these days.
Along with the moisture models prog a weak trough to move through
Saturday evening into Sunday afternoon. This will likely enhance
convection Saturday evening and allow storms to sustain themselves
through the overnight hours. Depending on how the overnight
activity plays out storms Sunday could be delayed due to cloud

Monday into Tuesday the upper level pattern begins to change with
a trough moving onshore from the Pacific. Moisture will still be 
in place both of those days with isolated to scattered showers 
and thunderstorms possible mainly from Tucson eastward. Better
moisture will be in place Monday along better dynamics, so expect
greater coverage of storms Monday than Tuesday. As the trough
moves off to the east southern Arizona will stay under
southwesterly flow which will scour out most of the moisture. This
will lead to just a slight chance of precipitation mainly in the
White Mountains and along the AZ/NM border Wednesday and 

Temperatures will be right around normal Sunday into Tuesday with
a slight warming trend Wednesday into the end of the work week.


.AVIATION......Valid through 15/00Z. 
SCT-BKN clouds 8-12k ft MSL this afternoon. ISOL-SCT -TSRA/-SHRA 
this afternoon into this evening E and S of KTUS with gusty 
outflow winds possible near storms. Another round of storms is
expected Saturday afternoon. SFC wind generally ELY/SELY 8-12 kts
through the period with occasional gusts possible Saturday 
morning. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Moisture returns today into into early next week.
Expect isolated to scattered showers and thunderstorms from Tucson
eastward today. Saturday and Sunday coverage and intensity of
storms expands to most of southeast Arizona. Early next week
moisture starts to move out with isolated to scattered storm
coverage from Tucson eastward. 20-ft winds will have an easterly 
component today into the weekend, but otherwise follow diurnal 
trends with speeds less than 15 mph. Gusty outflows will be 
possible near thunderstorms.




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