Scientific Forecaster Discussion
fxus65 ktwc 172129
Area forecast discussion
National Weather Service Tucson Arizona
229 PM MST Mon Jun 17 2019
Synopsis...dry conditions with seasonable daytime heat into next
weekend. Breezy at times late in the week.
Discussion...on the larger scale it's a fairly amplified pattern
for mid June with strong high pressure off the West Coast and a
weak split creating troughiness to our northwest over the Great
Basin, and a ridge downstream over the Southern Plains and
portions of eastern Mexico. As a result, we continue to have a
dominant westerly component to our flow that is keeping any large
scale processes from importing deep moisture into Southeast
Arizona. Actually, on the Pacific side of things the nearest deep
moisture is all the way down in southern sinaloa associated with a
deepening marine layer.
For US that means we will keep seeing periodic shallow moisture
intrusions from the Gulf of California, but they will typically
mix into little more than weak afternoon cumulus fields.
Temperatures will continue near or even a couple of degrees below
average as see another weak trough over the weekend.
It's Worth noting that ensembles point toward a deeper and more
consolidated inland moisture field across central to north-central
Mexico early next week. With a busier Durango, we would then start
to see some progress in southern portions of Chihuahua and Sonora
later next week.
Aviation...valid through 19/00z.
Scattered-few clouds at 20k-25k ft mean sea level moving to the northeast across Southeast
Arizona. Surface wind southerly/southwesterly at 12-18 kts with gusts to around 25 kts
through early this evening, with the strongest surface wind east of
ktus. Winds will be light and variable overnight. Southwesterly winds start
to increase again beginning 18/18z through approximately 19/00z.
Aviation discussion not updated for taf amendments.
Fire weather...dry conditions and average to below average
temperatures are expected across most of Southeast Arizona through
the forecast period. Afternoon relative humidity values will be
between 6-15 pct with fair overnight recoveries. Slightly elevated
20-foot south to southwest winds are expected through early this
evening across eastern areas, with speeds of 15-20 mph and gusts to
around 25 mph. Stronger, southwesterly winds then expected areawide on
Friday, but the strongest winds will be east of a line from Nogales
to Safford. Otherwise, 20-foot winds will generally be 15 mph or
less. Expect occasional gusts each afternoon and early evening due
to strong surface heating.