FXUS65 KTWC 170927

Area Forecast Discussion
National Weather Service Tucson AZ
225 AM MST Tue Oct 17 2017

.SYNOPSIS...A few showers are possible late this afternoon and
evening across southern Cochise county. Otherwise look for an
increase in high clouds today with continued well above normal high
temperatures. A fast moving disturbance will bring isolated showers
and thunderstorms Wednesday night into Thursday, mainly north and
northeast of Tucson. Expect some minor cooling Friday and Saturday,
then very warm temperatures return early next week as high pressure
aloft builds over the area.


.DISCUSSION...Satellite imagery this morning showed high clouds
approaching the area from the SW in advance of a upper level
disturbance that was about 400 miles west of the Baja Spur. These
high clouds, thick at times later this afternoon, will move across
the area today. PW values this morning across the area where
generally in the 0.50" to 0.75" range with higher values to an inch
across Sonora MX. Some of this higher PW values to our south will
advect north into the far southern areas near the International
border today and combined with daytime heating and weak wave pushing
thru, could develop areas of virga or light showers across the
southern portions of Cochise county late this afternoon into this
evening. The 00Z NAM and 00Z GEFS producing some light QPF along the
border and can`t rule out a lightning strike or two. Thus went ahead
and introduced slight chance PoPs to srn Cochise county late this
afternoon into early this evening. Even with the increase in cloud
cover later today will see another day of well above normal mid-
October highs.

An weak upper level trof will push across the state Wednesday night
into Thursday with a slight chance of light showers, possibly a t-
storm north-northeast of Tucson. Well above normal high temperatures
to continue Wednesday and Thursday.

Dry zonal flow over the area Friday and Saturday with slight cooler
daytime temperatures but still remaining above normal. Cooler
overnight lows Sunday and Monday mornings with a few of the colder
spots east of Tucson seeing lows in the low to mids 30s.

Daytime temperatures ramp back up to well above normal early next
week as strong high pressure aloft builds over the area.


.AVIATION...Valid thru 18/12Z.
FEW-SCT clouds at 8-12k ft AGL and SCT-BKN clouds above 20k ft AGL
thru the forecast period. Between 17/21Z and 18/06Z, there will be a
slight chance of -TSRA/-SHRA, mainly east of KFHU to KSAD line. SFC
wind will be ely/sely at 5-15 kts with some gusts to near 20 kts
thru 17/17Z, with SFC wind aft 17/17Z less than 12 kts. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...A weak disturbance will result in a slight chance of
showers and thunderstorms into Thursday, mainly during the afternoon
and evening hours. Otherwise, dry conditions will prevail into the
middle of next week. There will be some gusty east to southeast
winds through the late morning hours today, followed by normal
diurnal wind trends during the latter part of the week and into next
week. Expect occasional afternoon gusts due to daytime heating.





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NWS TWC Office Area Forecast Discussion