Scientific Forecaster Discussion
fxus65 ktwc 230418
Area forecast discussion
National Weather Service Tucson Arizona
917 PM MST sun Oct 22 2017
Synopsis...near record temperatures are anticipated for Monday,
gradually decreasing through the remainder of the week, albeit still
remaining above normal. Dry conditions also persist, with a period
of strong easterly breezes on Tuesday into early Wednesday.
Discussion...satellite imagery indicates clear skies across
southeastern Arizona this evening. The 500mb pattern is
characterized by an unseasonably strong 594dm high centered over
northern Baja California. After near average high temperatures on
Saturday, thicknesses have been increasing and some sites
experienced up to a 10 degree boost in high temperatures today. This
trend continues Monday and with the help of light easterly downslope
flow, near record heat will settle across the region.
Although warm temperatures remain the dominant story, clear skies,
dew points in the 20's and light winds will result in enhanced
radiative cooling tonight. Isolated areas in the eastern portion of
this forecast area may see brief freezing conditions, especially in
the Willcox/Sulphur Springs Valley region. For further details on
the upcoming days, please see the previous discussion below.
Aviation...valid thru 24/06z.
Clear skies and surface wind generally northeasterly-southeasterly less than 12 kts
through the forecast period. Aviation discussion not updated for taf
Fire weather...dry conditions will persist through the week.
High temperatures will warm and surpass record values for Monday and
reach near record values again on Tuesday before a gradual cooling
trend begins. Light easterly winds on Monday strengthen from the
east/southeast on Tuesday and Wednesday, with gusts to 25-30 mph
likely at times. Winds will turn west/northwesterly Thursday and
Friday and become breezy once again, especially for areas east of
Climate...record or near record high temperatures are likely across
Southeast Arizona Monday and Tuesday with Monday being the hottest
of the two days. This late October hot temperatures are due to an
unseasonably strong ridge of high pressure aloft over the area.
In addition to daily records being approached or exceeded on
Monday, the Tucson International Airport may also set latest in
the year records.
The current forecast has a high on Monday of 97 degrees at the
Tucson International Airport. If that occurs, it would be the second
latest occurrence of 97 on record. There is also a small chance on
Monday that the high at Tucson International Airport could hit 98.
Tucson International Airport
Mon Oct 23 96 94
Tue Oct 24 93 96
Latest 97+ high date in tucson: October 27, 2016.
Latest 98+ high date in tucson: October 19 in 1921 & 1991
Previous discussion /152 PM MST/...the severe clear skies and
warm temps over Arizona are the result of an upper level ridge
building across the western U.S. As a deep trough develops across
the eastern part of the country. The ridge will build quickly with
high temps on Monday 6-9 degrees warmer than this afternoon. Our
forecast high temperatures (more typical of the first week of
september) exceed records in several locations including the Tucson
Tuesday will remain clear with an east breeze developing as a cool
front slides west across the area. This cooler air will be battling
the sun and downslope flow (a warming effect) resulting in a modest
3-6 degree cooling from our record highs Monday afternoon. The
breezy east winds will continue into Wednesday and with continued
cool advection the highs will be few degrees cooler even after
milder low temperatures that morning due to the overnight breeze.
The model disagreement in the Thursday Onward period is becoming
less so and as expected is converging toward a not as cool solution.
The GFS remains the most consistent with only slight changes toward
higher heights while the overly cool, by comparison, earlier runs of
the European model (ecmwf) are gradually coming more in line with the GFS solutions.
The take-a-way is the trend is not as cool and have tweaked
temperatures slightly upward next weekend. We will be closer to
average next weekend however it will remain about 3-5 degrees warmer
than what is expected for late October. At this time I don't see
much of any chance of precipitation through the rest of the month.