Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 221620

Area Forecast Discussion
National Weather Service Tucson AZ
Issued by National Weather Service PHOENIX AZ
920 AM MST Thu Mar 22 2018

.SYNOPSIS...Expect near record temperatures this afternoon
especially from Tucson eastward. Mainly dry conditions with a
cooling trend will then prevail Friday through Monday. A low
pressure system will bring a slight chance of valley rain and
mountain snow mainly east of Tucson by the middle of next week.


Near record temperatures are still on track for this afternoon
with highs near 90 degrees. Southwesterly flow aloft will
continue for our area which is the primary facilitator for these
warm temperatures. A plethora of thick clouds will invade the
region later today but those should hold off late enough to allow
for some additional daytime heating. Please see the previous
discussion for additional details.


.PREV DISCUSSION... /issued 450 AM MST Thu Mar 22 201

Upper ridge axis extended from southwestern New Mexico northward
into Montana early this morning. Meanwhile, a deep upper low was
near the Washington coast with trough axis extending southward
essentially adjacent 130W. IR satellite imagery depicted an
expansive area of colder-topped clouds extending from just east of
the upper trough axis eastward into the southwestern CONUS.

Southwesterly flow aloft will increase today as the upper ridge axis
moves eastward, and the upper trough axis moves eastward toward the
California coast. Despite the expected fairly thick mainly cirriform
clouds, high temps this afternoon will be near record readings
particularly from Tucson eastward to the New Mexico state line.

22/00Z NAM12/GFS/ECMWF/CMC continue to trend lower regarding precip-
potential within this forecast area later tonight into early Friday.
Have maintained a slight chance of showers late tonight and Friday
morning near the White Mountains, but any measurable rainfall will
be just a few hundredths of an inch across the higher peaks. Have
noted that the NAM12 and the ECMWF depict light rain amounts to
occur Saturday mostly near the international border adjacent Cochise
County. At this time have discounted measurable rainfall from
occurring Saturday, so dry conditions should prevail area-wide
Friday afternoon into Monday as an upper trough deepens over the
intermountain west.

The 22/00Z deterministic GFS/ECMWF/CMC depict a generally 550 dm low
to be centered over west-central around daybreak Tuesday. This upper
low is then progged to move only very gradually eastward into east-
central Arizona or western New Mexico by midday next Wednesday.
These solutions have trended slightly eastward with the upper low
position versus solutions from 24 hours ago. Although model moisture
field values are somewhat lacking, fairly stout height falls should
be sufficient to translate into potentially gradually increased
precip coverage by next Wednesday. At any rate, there is a slight
chance of snow showers mainly near the White Mountains Monday night
through Tuesday night. A slight chance of valley rain/mountain snow
showers then exists mostly from Tucson eastward next Wednesday.

After the near record high temperatures today, a pronounced cooling
trend begins Friday and continues into early next week. High
temperatures next Tuesday are forecast at this time to be mainly 20-
25 degrees cooler versus today`s unseasonably warm temperatures.


.AVIATION...Valid thru 23/12Z.

Isolated -SHRA may occur near the White Mtns northeast of KSAD late
tonight into Friday morning. Otherwise, FEW-SCT clouds 12k-15k ft
AGL and BKN-OVC clouds above 20k ft AGL thru the period. Surface
wind this afternoon and early evening swly to nwly 10-20 kts with
gusts to near 25 kts. Surface wind at other times generally sely/sly
less than 10 kts. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...A few showers may occur across the White Mountains
late tonight into Friday morning. Otherwise, dry conditions into
Monday. A low pressure system will then bring a slight chance of
valley rain and mountain snow Tuesday into Wednesday mainly east of
Tucson. Gusty southwest to northwest afternoon winds will occur into
early next week. Critical fire conditions may also occur during the
afternoon hours Saturday through Monday especially near the
Chiricahua Mountains in eastern Cochise County. However, conditions
at this time are next expected to be long-lived. Less wind should
generally prevail next Tuesday and Wednesday.


.CLIMATE...Here is a table of forecast high temperatures and record
high temperatures today:

                              March 22
                         Forecast  Record/Year
TUCSON INTL AIRPORT         90       90/1990
BISBEE-DOUGLAS AIRPORT      87       87/2017
AJO                         89       97/2004
KITT PEAK                   72       75/2004
ORGAN PIPE CACTUS           85       95/2004
PICACHO PEAK                89       94/2004
SAFFORD AG STATION          86       88/1997
SIERRA VISTA FD             83       86/2017
TOMBSTONE                   85       87/1999
WILLCOX                     85       87/2017






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