Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 251020
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
320 AM MST Wed Apr 25 2018

.SYNOPSIS...Dry conditions with unseasonably warm daytime
temperatures through midweek. Increased moisture will then bring
isolated to scattered showers and thunderstorms mainly east of
Tucson Friday into Saturday. Dry conditions to return Sunday, with
next week shaping up to be a little cooler and windy at times.

&&

.DISCUSSION...Another week low off the eastern Pacific is bringing
a few clouds to the area today. Only virga on this side of the
border with the light shower activity remaining in northern
Mexico. Otherwise strong high pressure will bring another day of
temperatures around 10 degrees above average, with these warm
temperatures continuing into the weekend.

The main story continues to be the convection Friday and
Saturday. Moisture spreading in from the east and southeast the
second half of the week will combine with strong solar insolation
and weak mid level cooling in the wake of the ridge axis shifting
to our east. Confidence is increasing as more GEFS plume members
lean toward operational ECMWF resolutions. Also, more and more NCEP
SREF plume members are showing the increased moisture and MU/ML
CAPE Friday afternoon into Saturday afternoon. High based storms
with dry microburst potential still a concern.

With the newly consolidated flow, we will be ripe for a pattern
change early next week with a potential mean trough position
being established through western states. This will shunt our
moisture eastward as early as Sunday. It will also trend us
toward cooler temperatures and gusty winds by Monday.

&&

.AVIATION...Valid through 26/12Z.
Scattered to overcast clouds above 13k ft AGL becoming few to
scattered cirrus clouds this afternoon and continuing into early
Thursday morning. Surface wind this afternoon and early evening west
to northwest 8-15 kts with occasional gusts near 20 kts. Surface
wind variable in direction mainly under 10 kts at other times.
Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Light winds and dry conditions into early
Thursday, then increased moisture from the east brings a slight
chance of thunderstorms over the White Mountains Thursday afternoon
and evening. Sufficient moisture for isolated to scattered mainly
afternoon and evening thunderstorms from Tucson eastward Friday into
Saturday.

The main concern Friday into Saturday is thunderstorms capable of
starting fires and producing strong outflow winds, especially in the
higher terrain where development is more likely. Dry conditions will
then prevail Sunday into Tuesday.

20-foot winds terrain driven less than 15 mph through Thursday.
Gusty east to southeast winds from Tucson eastward Friday morning
should occur before potentially gusty thunderstorm outflows Friday
afternoon into Saturday. Gusty south to southwest winds are on tap
Saturday into Monday. Critical fire conditions may return Monday
particularly across mountains from Tucson southward and
southeastward into Santa Cruz/Cochise Counties.

&&

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

&&

$$

Meyer/Francis

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