Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 261015

Area Forecast Discussion
National Weather Service Tucson AZ
315 AM MST Sat May 26 2018

.SYNOPSIS...Dry conditions through next Friday. Daytime temperatures
except for Sunday will be a few to several degrees above normal.
Expect gusty winds this afternoon followed by less wind during the
upcoming week.


.DISCUSSION...IR satellite imagery and surface observations depicted
broken to overcast cirriform clouds across southeast Arizona early
this morning. The colder topped clouds generally extended from the
White Mountains southwestward into western Pima County, and
continued further southwest into northern Baja California.
Meanwhile, more extensive breaks in the cloud mass were noted over
central/southern Sonora Mexico.

The upper level pattern early this morning is defined with a closed
upper low over the Great Basin, and a ridge axis that extends from
near El Paso Texas northward into eastern Montana. The upper low is
progged to move very slowly eastward today, and become centered near
the eastern Nevada/western Utah state lines early Sunday.

A fairly tight mid-level pressure gradient around the southeast
periphery of the upper low will produce gusty southwest to northwest
winds this afternoon and early evening. Although wind speeds will
remain below wind advisory criteria, the gusty winds in combination
with very low relative humidity will create critical fire conditions
across portions of the White Mountains. A Red Flag Warning is in
effect from noon today to 7 pm MST this evening. Please refer to the
Fire Weather section for further information.

Have noted that a few NAM12 solutions have depicted at times a few
hundredths of an inch of rainfall to occur across portions of
Cochise County today. These solutions have been discounted given the
very dry surface-700 mb (and perhaps even to 600 mb depending upon
numerical model) layer. Perhaps some virga may ultimately occur east
of Tucson later today. Otherwise, dry conditions will prevail area-
wide as clouds decrease later today followed by clear skies to
mostly clear skies by daybreak Sunday.

The upper low will remain quasi-stationary Sunday then fill while
lifting northeastward into the northern Rockies Monday. A southwest
to west flow aloft regime should translate into additional cirriform
clouds to move across the area Monday night into Tuesday. Thereafter,
a generally southwesterly flow aloft regime will prevail Wednesday
into Friday as an upper trough amplifies over the Great Basin to
near the West Coast. This pattern will provide generally clear skies
except for some cirrus about next Thursday.

After the gusty winds today, less wind will prevail starting Sunday
and continue during the upcoming week. Daytime temperatures into
next Friday will range from a few to several degrees above normal.
The exception will be Sunday when high temps will trend quite close
to seasonal normals.


.AVIATION...Valid through 27/12Z.
Mainly broken clouds above 15k ft AGL today. Decreasing clouds this
evening with clear skies to few cirrus clouds by daybreak Sunday.
Surface wind this afternoon and early evening swly to nwly 10-25
kts with gusts near 35 kts. The strongest speeds will be east of
KTUS to the New Mexico state line. Surface wind variable in
direction mainly less than 12 kts at other times. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...A Red Flag Warning is in effect from noon today to 7
PM MST this evening for the northern half of Fire Weather Zone 153.
The combination of strong and gusty southwest winds, low relative
humidity and a very high fire danger will create critical fire

Critical fire conditions may also occur this afternoon east of
Tucson, and especially across the Chiricahua Mountains in eastern
Cochise County and near the New Mexico state line. However,
conditions are not expected to widespread nor long-lived.

Otherwise, dry conditions will prevail through next Friday. Expect
less starting Sunday and continuing during the upcoming week.
However, occasional afternoon and early evening gusts will occur due
to strong daytime heating.


.CLIMATE...Based on current forecast temperatures for Tucson through
the end of the month, May 2018 will likely rank around the 11th
warmest on record.


Red Flag Warning from noon today to 7 PM MST this evening for AZZ153.




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