Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Tucson Arizona
347 am MST Monday Jan 26 2015

Synopsis...increasing moisture from the south will bring thickening
clouds and showers to southern Arizona today into early Tuesday. Dry
and warmer middle week before a stronger Pacific system brings valley
rain and mountain snow to the area late Thursday through the weekend
with the best chances occurring Friday and Friday night.

&&

Discussion...water vapor imagery and 26/00z upper-air plots show
high pressure over the Great Basin and an upper low offshore of the
Southern California and northern Baja California coasts...generally in the
vicinity of 29.3 degrees north latitude and 123.2 degrees west longitude. With
this setup the combination of the clockwise flow around the high and
counter-clockwise flow around the low...the pump has been primed for
significant moisture to spread north and northwest into the Desert
Southwest.

Yesterday evenings ktwc sounding revealed a precipitable water value
of only 0.28 inches. However...as of 0845z...which was the latest
image from the satellite derived blended total precipitable water
product...the precipitable waters over extreme southern Arizona ranged from around
0.20 to 0.40 inches over the northeastern half of my forecast area
to just over a half inch from Tucson and southward along the
international border. The GPS precipitable water vapor values from
the u of a showed a value at just over a half inch at Tucson as of
0845z. That said...values of 1.2 - 1.4 inches are over southern
Sonora and as the day progresses this moisture will make its way
into Arizona.

Models forecast precipitable water values to increase to around a half inch across the
northeastern portion of the forecast area over the White Mountains
of east central Arizona to 1.2 inches for the far western deserts of
Pima County near Ajo and Organ pipe. Generally speaking most areas
will see precipitable waters rise to around the 1 inch mark late today into this
evening...which will be about 3 Standard deviations above normal.
The bottom line is that we will see wet weather across southern
Arizona today through early Tuesday.

The latest radar mosaic loop shows showers mostly south of the
border in northwest Sonora and these showers are moving to the
northwest toward Yuma. A few of these showers will spill over into
Arizona early this morning...but the bulk of this precipitation will
occur this afternoon and into the evening hours as the low to middle
level flow becomes more southerly. That said...the showers will
continue to occur over the extreme southwestern portion of Arizona
and spread to the northeast as the day wears on. The bulk of the
precipitation should occur late this afternoon and into much of the
evening hours...with numerous showers over the deserts and valleys
and widespread showers for the mountains. Quantitative precipitation forecast values will range from
around a quarter to a third of an inch for areas along the New
Mexico border and from a third to a half inch for the remainder of
the forecast area. Mountain locations should see amounts of around a
half inch to near an inch. This system is a warm one...so no real
threat for snow. Perhaps a dusting over the highest peaks in the
White Mountains of northern Greenlee County early Tuesday...but that
should be all.

Once this system lifts to the north late Tuesday a return to dry
weather for Wednesday and much of Thursday before another Pacific
system brings precipitation to the region Thursday night through the
weekend...but the best chances will occur Friday and Friday
night.

For Tucson...high temperatures will generally be near normal
today...then about 3 to 5 degrees above normal for Tuesday and 7 to 9
degrees above normal for Wednesday and Thursday. Thereafter...highs
around 4 to 6 degrees below normal. Low temperatures will be well above normal
throughout the forecast period...but the warmest mornings will occur
Thursday and Friday when lows will be 10 to 12 degrees above normal.

&&

Aviation...valid through 27/06z.
High clouds mainly above 20k feet above ground level will continue through 26/15z. After
26/15z west and S of an Ajo to Green Valley line...sct-bkn 6-10k feet
moving in from the S along with scattered -shra. Local MVFR conds near -shra.
As the day progresses these conds will slowly move to the N-NE. East-southeast
surface wind at 10-15 kts. Aviation discussion not updated for taf
amendments.

&&

Fire weather...east to southeast winds will occur across much of
the area over the next couple of days. Wind speed will be in the
10-15 miles per hour range...with a few higher gusts. Scattered showers will be
moving across the area today into tonight. Dry weather will return
Tuesday afternoon through Thursday before another Pacific storm
brings a good chance of showers Friday into next weekend.

&&

Twc watches/warnings/advisories...none.

&&

$$

Visit US on facebook...twitter...youtube...and at weather.Gov/Tucson

Public...mollere
aviation/fire weather...glueck

National Weather Service Glossary of Abbreviations