Area Forecast Discussion
Issued by NWS Tucson, AZ
FXUS65 KTWC 251629
Area Forecast Discussion
National Weather Service Tucson AZ
929 AM MST THU AUG 25 2016
.SYNOPSIS...Increasing moisture will help create better
thunderstorm coverage by Friday and Saturday. Watch for strong
storms with possible areas of blowing dust.
.DISCUSSION...A transition day as we lose the strong northwesterly
to northerly flow below 500mb and start to pick up a little more
moisture. The 12z KTWC sounding reflects this well. Precipitable
water values are now pushing back above 1 to 1.1 inches and
climbing. Surface dew points across the area this morning are up 4
to 7 degrees compared to 24 hours ago; solidly back into the 50s.
Enough for a few storms this afternoon that will tend to want to
hug the mountains for support.
Still on track for a strong upswing in thunderstorm coverage and
probably intensity as well Friday and Saturday. Please see the
previous discussion below for additional details.
.AVIATION...VALID THRU 26/18Z. VFR conditions through the
forecast period. Isold -TSRA/-SHRA developing after 25/19z mainly
near the mountains. Clearing skies expected aft 26/04z. Surface
wind generally less than 12 kts with normal diurnal trends.
Aviation discussion not updated for TAF amendments.
.FIRE WEATHER...Isolated thunderstorms will occur mainly near
mountains today. Increasing storm coverage with a moisture
increase Friday through early next week. 20-foot winds through
the upcoming weekend will be terrain driven and less than 15 mph
in most locations. Expect the potential for strong and gusty winds
near any thunderstorms that do develop.
.PREV DISCUSSION...Clear to partly cloudy conditions prevailed
across SE AZ this morning. Precipitable water values this morning
similar to yesterday. Scattered thunderstorms over the higher
terrain east of Tucson and along the international border,
especially around Nogales. Sonora should be more active this
evening with some of that moisture advecting north across the area
late tonight into Friday. Upper level trofiness to our west will
keep southerly flow over the area this weekend. Thus Friday
through Sunday will be the most active thunderstorm days in the 7
day forecast package. Highs right around normal today then several
degrees below normal Fri-Sun.
Warmer early next week, but not as warm as what was previously
forecast. Each day will see isolated to scattered
showers and thunderstorms.
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