Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 210343
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
843 PM MST Tue Aug 20 2019

.SYNOPSIS...Hot, near or above record high temperatures will be
around once again on Wednesday with dry conditions for most of the
area. Increasing moisture will bring increasing thunderstorms to
the area with temperatures falling back to near normal by Friday
into the weekend.

&&

.DISCUSSION...Several heat records fell around the area today, but
Tucson Airport came up 1 degree short. More of the same for much
of the area tomorrow, however a moisture increase is underway with
outflows from New Mexico pushing into Cochise county this evening.
Easterly winds around 15kts at Douglas and dew points jumped from
38 to 49 over the past 90 minutes. Our moisture increase from
direct outflow from the east and south, and a moderate gulf surge
working it`s way into the northern Gulf. We should be back in
business with a strong fetch of deeper moisture Thursday night
into Friday and Saturday. A strong increase in thunderstorms and
temperatures falling back to near normal is still a solid forecast
trend. Please see the previous discussion below for additional
details.

&&

.AVIATION...Valid through 22/06Z.
FEW-SCT clouds at 12k-16k ft MSL thru the forecast period. There
is a slight chance of -TSRA/-SHRA near the AZ/NM border including
near KDUG and across the White Mountains into late this evening.
ISOLD- SCT -TSRA/-SHRA redevelop Wednesday afternoon from
KTUS/KOLS eastward. SFC wind generally NWLY into this evening at
less than 12 kts with a few gusts to 15-20 kts. Terrain driven
winds less than 10 kts persist overnight with SW to NW winds
Wednesday afternoon mainly less than 12 kts. Aviation discussion
not updated for TAF amendments.

&&

.FIRE WEATHER...Better coverage of showers and thunderstorms
begin tomorrow mainly east of Tucson and spread westward and
northward into Saturday. Near record high temperatures are
expected through Wednesday, but the return of deeper monsoonal
moisture will allow temperatures to fall back to near seasonal
levels by Friday. Any thunderstorms that do develop may produce
gusty and erratic outflow winds. Otherwise, 20-ft winds will
generally follow normal diurnal trends at less than 15 mph.

&&

.CLIMATE...Another day of record to near record highs tomorrow
across southeast Arizona. Below are the forecast highs for
Wednesday versus the daily record highs for selection locations
across southeast Arizona.

DATE                         Aug 21
                          FCST RCD/YR
Tucson Intl Airport       109 108/1930
Bisbee-Douglas Airport     98  98/2011
Ajo                       111 115/1915
Kitt Peak                  91  86/2010
Organ Pipe Cactus N.M.    111 112/1969
Picacho Peak              109 108/1999
Safford Ag Station        105 105/1986
Sierra Vista               97  97/2013
Tombstone                  98 101/1938
Willcox                   100 105/2009

Temperatures cool to near normal over the weekend before warming
up once again early next week with near record highs possible next
Tuesday.

&&

.PREV DISCUSSION... /issued 220 PM MST Tue Aug 20 2019/
Very hot for August with record to near record high temperatures
around today and once again tomorrow. Excessive Heat Warning is in
effect until 8 pm Wednesday for the lower elevations of Pima,
Pinal and Graham counties. Moisture limited across the area today
with values mostly less than 1". The exception is right along the
AZ/NM border where values are slightly above 1". So a few storms
possible along the AZ/NM border and also along the Intl border
east of Nogales.

For tonight, will see low level moisture values increase
associated with outflows coming out of New and old Mexico. The
outflow out of New Mexico may generate a few showers/storms across
Cochise county later tonight that may persist into Wednesday
morning, per UofA WRFNAM.

Wednesday: PWAT values increasing into the 1" to 1.30" range with
highest values south of Tucson. This will result in an increase
in thunderstorms, in the isolated to scattered range mainly south
and east of Tucson.

Thursday: PWATs will be ranging from 1" east to over 1.5" west
with best chances for storms being west and south of Tucson.
Localized heavy rainers with light and variable steering flow.

Friday: the steering flow becomes more easterly across the area
and combined with PWAT values similar to Thursday and a weak
inverted trof passing through Sonora looking at the most active
convective day in almost two weeks with the potential for activity
to continue into the overnight hours.

Saturday: Upper level ridge axis north of the area will put the
area under NE flow aloft which will bring an increasing chance
for a rim shot event.

Sunday: Lingering moisture around for the chance of afternoon and
evening storms.

Monday and Tuesday: Conditions start to dry out with lowering PWAT
values as upper high center settles over the area.

Temperatures will be cooling later in the week and continuing
into the weekend where highs could be at or a few degrees BELOW
normal. That will be short lived as highs warm back above normal
early next week with the potential for near record highs once
again next Tuesday.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM MST Wednesday for AZZ501-502-
504>506-509.

&&

$$

Meyer/G/C

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