Frogville´s Weather Service

Updated:  20-Apr-2026 3:20am 
  mostly clear Temperature: 64.8°F   -3.2°F/hr Humidity: 31% Dew Point: 33.4°F Wind: E  0.3 mph Gust: 1.0 mph Barometer: 29.830 inHg   Steady Rain Today: 0.00 in UV Index: 0.0  None

265
FXUS65 KTWC 200801
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
101 AM MST Mon Apr 20 2026

.SYNOPSIS...Modest mid-level moisture will result in a chance
of mainly dry storms/thunderstorms this afternoon near the White
Mountains. Otherwise, warm and dry for much of the week and into
the weekend. Breezy conditions are anticipated for the second
half of the week into this weekend, resulting in near critical
fire weather conditions east of Tucson Wednesday through Friday.

&&

.DISCUSSION...In the short term, the latest GOES blended total
precipitable water imagery indicated a slug of deeper moisture
with PWAT values between 0.5-0.75 inches situated across Pinal
and eastern Pima county this morning. A weak shortwave observed
on GOES-19 water vapor imagery across the backside of a weak
trough moving NE through southwest Arizona this morning will
interact with this moisture as it tracks into the east central
mountains of Arizona this afternoon. The lower-levels are still
rather dry, but there should be enough lift and instability to
produce a chance (30-40%) of mainly dry storms/thunderstorms
over the White Mountains this afternoon with gusty and erratic
winds accompanying the downdrafts.

Otherwise, the upper pattern is defined by a strong upper-low
off the coast of the Pacific Northwest/northern California this
morning. There is strong agreement with the ensemble members of
both the GEFS and ECMWF with tracking this upper low into NRN CA
by 22/00Z Tuesday afternoon and through the NRN Great Basin
Wednesday. As this occurs, a high-amplitude ridge of high
pressure building off the coast of British Columbia Canada will
force the development of a weak low to its south, creating a
mean open trough with an axis extending from just off the
central CA coast into the NRN Rockies Friday. This orientation
is conducive for progressive shortwaves to zip by to our north
in the nearly zonal upper flow. The low itself weakens and then
moves through southern California/northern Arizona early this
weekend. What does this all mean? Well, we will stay warm with
afternoon breeziness the second half of this week into next
weekend. The strongest winds will likely occur Friday and Saturday,
and is supported by the 20/04Z NBM probability between 30-40%
for wind gusts in excess of 25+ mph at the Tucson International
Airport (KTUS).

The main weather impact this week will be fire weather related
given the combination of low RHs and the breezy WLY winds. The
04/18Z NBM 5.0 probability for reaching critical fire weather
conditions (RH20 mph) across
portions of Fire Weather Zone 152 Wednesday through Friday is
50-70 percent. Given the uncertainty in the strength and timing
of the stronger winds, we will just message elevated to near
critical fire weather conditions for now.

&&

.AVIATION...Valid through 21/12Z. SCT 10-15k ft AGL decreasing
through 20/18Z, with a development of 8-12k ft AGL clouds to the
NE of KTUS (including the terminal at KSAD) in the afternoon
through 21/02Z. After 21/02Z, increasing high clouds AOA 20k ft
AGL from the southwest through the rest of the valid period.
Valid through 21/12Z. SFC winds light (less than 10 kts) and
terrain driven through 20/20Z, then SWLY/WLY 10-14 kts with
occasional gusts to 20 kts into the early evening. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...There is a modest increase in mid-level moisture
near the White mounatins will result in a chance (30-40%) for mainly
dry storms/thunderstorms this afternoon with gusty and erratic
outflow winds possible near the downdrafts. Minimum RHs will
generally be 10-15 percent in the valleys and 15-25 percent in
mountains today, decreasing to the single digits to mid teens
areawide by mid-week. Otherwise, passing systems to the north
this week will keep Southeast Arizona dry, but breezy the second
half of the week into next weekend. There is a 50-70 percent
probability that portions of Fire Weather Zone 152 will reach
elevated to near critical fire weather conditions Wednesday
through Friday.

&&

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

&&

$$

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NWS TWC Office Area Forecast Discussion