Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 220911

Area Forecast Discussion
National Weather Service Tucson AZ
211 AM MST Wed Feb 22 2017

.SYNOPSIS...Dry conditions will prevail through Sunday. Expect
well above normal high temperatures today with a few spots near
record highs. A weather system passing by to the north on Thursday
will bring much cooler temperatures to the area Thursday and Friday.
A warmup again this weekend before a strong Pacific storm brings a
chance of precipitation to the area on Monday and Tuesday.


.DISCUSSION...Latest water vapor satellite imagery shows ridging
aloft centered to the south of the area near Baja into southern
Sonora with west to southwest flow aloft across the area. Mostly
clear skies this morning with just a few very thin cirroform
cloudiness as the bulk of the clouds remain to the north of the
area. With ridging in place today, we are looking at a very warm day
with highs about 8 to 12 degrees above normal for this time of year.
A couple of spots will approach record highs this afternoon.

A shortwave trough will drop to the south and east through the Great
Basin and extend into Arizona tonight into Thursday, resulting in a
cold frontal passage. Even though there will be some increase in mid
and high level clouds with this system, it will remain dry this far
south with the main impact being a significant drop in temperatures
for Thursday into Friday. Expect highs to be upwards of 15 degrees
cooler compared to today. There will also be an enhanced pressure
gradient as well which will result in some breezy conditions for
Graham/Greenlee/Cochise Counties Thursday afternoon.

A fairly benign and dry weekend is expected with flat ridging and
dry conditions. As heights and thickness values bump up compared to
Thursday/Friday, a corresponding increase in temperatures through
the weekend will occur as well. Thereafter, a more significant
system is expected to drop down the West Coast into the Desert
Southwest early next week. Latest 00Z deterministic GFS/ECMWF/CMC
and GEFS ensemble is keeping the bulk of the precipitation chances
to our north and west through Sunday night, before overspreading the
area as the trough moves through Monday into Tuesday. As would be
expected, there are some timing and amplitude discrepancies this far
out, but the general trends for cooler temperatures, a chance for
rain and mountain snow along with some increased winds look good.


.AVIATION...Valid through 23/12Z.
Clear conditions this morning, then SCT-BKN clouds above 15k ft AGL
into Thursday morning. Light surface winds mainly less than 10 kts
thru 22/18z then becoming westerly 10-15 kts with gusts to 25 kts
through the afternoon. Aviation discussion not updated for TAF


.FIRE WEATHER...Highs will be about 8 to 10 degrees above normal
today, before returning to near normal Thursday and Friday as a
weather system passes north of the area. Surface winds will remain
light this morning, but will become gusty with daytime heating.
Expect gusty afternoon winds Thursday and Friday with the passing
system to the north.

Warmer and dry conditions will continue through the weekend with
afternoon winds picking up again Sunday afternoon.  A storm system
will approach the area Monday resulting in rather windy conditions
and depending on how slow the moisture is to arrive we could have
critically low humidity levels again across zone 152 with the winds
before any showers arrive.






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