Severe Thunderstorm Warning 101, NWS Tucson, AZ

068 
WWUS55 KTWC 032120
SVSTWC

Severe Weather Statement
National Weather Service Tucson AZ
220 PM MST Tue Sep 3 2019

AZC023-032145-
/O.CON.KTWC.SV.W.0101.000000T0000Z-190903T2145Z/
Santa Cruz-
220 PM MST Tue Sep 3 2019

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 245 PM MST
FOR SOUTHWESTERN SANTA CRUZ COUNTY...

At 220 PM MST, a severe thunderstorm was located near Rio Rico, or
near Nogales, moving southwest at 15 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees.

Locations impacted include...
Nogales, Rio Rico and Pena Blanca Lake. 

This includes the following highways...
 Interstate 19 between mile markers 1 and 12.
 Route 82 between mile markers 1 and 7.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 3134 11109 3135 11113 3142 11119 3152 11093
      3143 11085 3133 11090
TIME...MOT...LOC 2120Z 053DEG 11KT 3142 11095 

HAIL...<.75IN
WIND...60MPH
 
$$

Carpenter

156 
WWUS55 KTWC 032144
SVSTWC

Severe Weather Statement
National Weather Service Tucson AZ
244 PM MST Tue Sep 3 2019

AZC023-032154-
/O.EXP.KTWC.SV.W.0101.000000T0000Z-190903T2145Z/
Santa Cruz-
244 PM MST Tue Sep 3 2019

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHWESTERN SANTA CRUZ COUNTY
WILL EXPIRE AT 245 PM MST...
        
The storm which prompted the warning has weakened below severe
limits, and has exited the warned area. Therefore, the warning will
be allowed to expire.

LAT...LON 3134 11109 3135 11113 3142 11119 3152 11093
      3143 11085 3133 11090
TIME...MOT...LOC 2144Z 053DEG 11KT 3138 11101 

$$

Carpenter

Area Forecast Discussion
National Weather Service Tucson AZ
925 AM MST Tue Sep 3 2019

.SYNOPSIS...We will have a gradual downturn in thunderstorm coverage
through Friday with less moisture and hotter temperatures. An
expected increase in moisture should bring increasing storm chances
this weekend. Expect temperatures to remain above average through
the week with near record highs possible on Wednesday.

&&

.DISCUSSION...Mostly clear skies across southeast Arizona via
visible satellite this morning with surface temperatures mainly in
the low to mid 80s and dewpoints ranging from the mid-50s to low 60s
as of 03/16Z. Still expecting well above average temperatures this
afternoon with the majority of the CAMs consistent with isolated to
scattered convection developing mainly during the afternoon hours.
The 03/12Z KTWC RAOB supports this scenario with 1.36" PWAT, a
forecast 1800 J/kg of SB CAPE this afternoon and a LI of -5.
Shouldn't have too much trouble overcoming our morning capping
inversion with all this sunshine. Main concern with storms will be
downburst winds as is typical with DCAPE around 1700 J/kg and plenty
of dry air above H5. With mainly easterly flow through the column,
expect storms to form on the mountains before moving west into
valley locations. Storms will be a bit slow to move though with
steering flow of just around 5 kts, so we'll need to keep an eye on
rainfall amounts and flooding potential as well. The forecast for
today looks good so no updates this morning. Please see the
remaining sections for additional information.

&&

.AVIATION...Valid through 04/18Z.
Isolated to scattered SHRA/TSRA develop this afternoon, continuing
into the evening hours. FEW-SCT clouds 8k-15k ft MSL through the
period, and periodically BKN near TSRA with brief MVFR conditions
and gusty outflow winds up to 40 kts. Otherwise, SFC winds generally
remain below 12 kts through the forecast period favoring a NWLY-NELY
direction during the afternoon outside of any TSRA. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Isolated to scattered showers and thunderstorms
develop this afternoon, decreasing in coverage by Wednesday as drier
air overspreads the region. This allows temperatures to rise well
above normal for this time of year, with afternoon breeziness from
Tucson eastward. Generally dry weather persists for several days
until the pattern begins to shift over the weekend. Thunderstorm
activity becomes fairly widespread on Sunday continuing into the
start of next week.

&&

.CLIMATE...
Near record high temperatures the next 2 days for a few locations

DATE                         Sep 03           Sep 04                                             FCST RCD/YR      FCST RCD/YR      FCST RCD/YR
TUCSON INTL AIRPORT       103 107/1983     105 106/2011
BISBEE-DOUGLAS AIRPORT     96 102/1948      95 101/1952
AJO                       106 111/2002     106 111/2007
KITT PEAK                  84  87/1979      86  89/1979
ORGAN PIPE CACTUS         106 111/1982     106 109/1979
PICACHO PEAK              104 108/2010     106 109/2002
SAFFORD AG STATION        104 105/1982     102 106/1948
SIERRA VISTA FD            93  99/1917      94  98/2012
TOMBSTONE                  95 101/1983      95 106/1917
WILLCOX                    97 104/1948      96 105/1929

&&

.PREV DISCUSSION...It looks as though we are entering a down period
as far as convection is concerned, at least through Friday. Compared
to 24 hours ago, surface dewpoints are several degrees lower than 24
hours ago which is a bit of a negative. However, PW levels over
Tucson remain about 1.25" this morning, similar to yesterday and
actually the PW gradient over the area is tightening with values
increasing to the west which is a potential convective focus source.
As far as I can see, we appear to lack an upper level feature that
will help us this afternoon as a focus. Most CAM solutions and the
NAM do develop some storms in western Cochise, eastern Pima and
Santa Cruz counties this afternoon and then push them out to the
west where there is more favorable moisture. The area these storms
initially develop is in the enhanced PW gradient area that is
currently developing lending some confidence to that occurring. I
adjusted pops to account for that line of thinking. As is usually
the case there should be scattered storms developing over the White
Mountains as well which may push an outflow to the southwest. With
low/mid level thickness values similar to yesterday, high
temperatures will end up pretty close to what we had yesterday.

Wednesday through Friday, conditions are even a bit less favorable
for thunderstorm development thanks to a bit of drying and to
slightly warmer mid level temperatures. High temperatures will
continue to run 3-6 degrees warmer than average with the peak
occurring on Wednesday where forecast highs are within striking
distance of a few daily records.

By Saturday, the upper level high has weakened as an upper level
trough approaches the west coast resulting in cooling mid level
temps and a gradual increase in moisture. So we should have a slight
increase in storm coverage Saturday with a more significant increase
Sunday into Monday thanks to enhanced southerly flow with an upper
trough to the west-northwest and the upper level high east of Texas.
This will also allow for temperatures to finally drop to more
average early September levels (normal high for Tucson next Monday
is 96).

&&

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

&&

DISCUSSION...Carpenter
PREV DISCUSSION..Cerniglia
AVIATION....Howlett
FIRE WEATHER...Howlett

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