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fxus65 ktwc 191046 

Area forecast discussion
National Weather Service Tucson Arizona
345 am MST Wed Jun 19 2019

Synopsis...dry conditions will prevail into early next week. Expect
near normal daytime temperatures through Friday followed by
moderating temperatures this weekend as a low pressure system moves
north of the area. Hotter temperatures will return by next Tuesday
as high pressure aloft builds southeast of the area.


Discussion...a weak trough aloft prevailed across Southeast Arizona
early this morning. This trough was located between strong high
pressure aloft centered well west of the northern California coast
(near 36n/137w), and strong high pressure aloft centered over the
western Gulf of Mexico. Various 19/00z numerical weather prediction
models depict very little change in the upper level pattern through
Thursday. Thus, continued clear skies across much of Southeast
Arizona (some cirrus at times across far southeast sections) along
with relatively light winds.

The models depict a deepening upper trough will occur over the
western U.S. Friday into Saturday as strong high pressure aloft
remains stationary west of the California coast. A very dry regime
translating into clear skies is progged to continue across this
forecast area through this weekend. However, the main impact will be
a gradual daily cooling trend Friday into Saturday followed by no
significant change in daytime temps Sunday. Some gusty afternoon
winds will occur Friday and perhaps more noticeably Saturday in
response to a tightening mid-level gradient. Somewhat less wind
should occur Sunday as the mid-level gradient loosens.

Thereafter, the GFS/gefs and European model (ecmwf)/eps were quite similar with
depicting a light zonal flow aloft regime across the area Monday.
The models were very consistent with depicting strengthening high
pressure aloft southeast of this forecast area next Tuesday (gfs/
European model (ecmwf) depict 592 dm high centered over western chihuahua). This
pattern will likely translate into continued clear skies, but with
hotter temperatures returning early next week, and especially next
Tuesday which is day 7 of this forecast package.

Although beyond the scope of this forecast package, have noted the
19/00z GFS/gefs and European model (ecmwf)/eps were fairly similar with moving the
aforementioned western Chihuahua upper high northward to near the
New Mexico bootheel (gfs); or, even further northward toward The
Four Corners region (ecmwf) during the latter part of the next week.

This pattern suggests an increasingly favorable flow regime for the
potential development of showers and thunderstorms that may
primarily encroach upon eastern sections of this forecast area.
Also, forecast confidence is fairly high based on these solutions
that even hotter temperatures versus next tuesday's forecast high
temperatures will ultimately prevail by late next week. This
scenario of potentially increased moisture across eastern sections,
and hotter temperatures especially from Tucson westward, is
plausible if these solutions ultimately become reality.


Aviation...valid through 20/12z.
A few clouds above 20k ft mean sea level across far Southeast Arizona or
especially near kdug into this afternoon. Otherwise, sky clear into
Thursday morning. Surface wind this afternoon wly/nwly 10-18 kts
with occasional gusts of 20-25 kts. Strongest speeds expected
vicinity ksad. Surface wind variable in direction under 10 kts at
other times. Aviation discussion not updated for taf amendments.


Fire weather...dry conditions will continue through next Tuesday.
Afternoon minimum relative humidity values through Friday will
generally range from 5-15 percent with fair overnight recoveries.
Daytime minimum relative humidity values this weekend will mainly
range 10-20 percent followed by lower daily ranges by next Tuesday.
20-foot winds mainly terrain driven under 15 mph, although afternoon
gusts due to daytime heating. However, somewhat stronger southwest
winds will occur Friday and Saturday as a low pressure system moves
north of the area.


Twc watches/warnings/advisories...none.


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