Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 191648

Area Forecast Discussion
National Weather Service Flagstaff AZ
948 AM MST Sat Aug 19 2017

.SYNOPSIS...Dry conditions will continue across most of northern
and central Arizona today. There will be a slight chance of
showers and thunderstorms over the White Mountains this afternoon
and evening. Higher chances of showers and thunderstorms then move
back north and west, affecting much of the area by Sunday and
into next week.


.DISCUSSION...Visible satellite imagery shows generally clear
skies across northern Arizona this morning. There are some mid
and high clouds streaming into the White Mountains from the south.
The 12z RAOB from Bellemont remained quite dry with a
precipitable water value of 0.42 inches. This was similar to
yesterday mornings sounding. However, one key difference was a
shift to southerly flow below 500 mb. As has been expected for
the past several days, this will result in increasing moisture
across the area this weekend and into early next week. We still
are expecting shower and thunderstorm activity to be confined to
the White Mountains this afternoon, but convection will become
more widespread Sunday and continue early next week. The current
forecast handles this well so no changes are needed at this time.


.PREV DISCUSSION /435 AM MST/...Moisture continues to increase
across Arizona as more favorable southerly flow pattern develops.
We expect several days of this southerly flow, due to a somewhat
unusual low off the southern California coast and high pressure
over Texas. MCS activity over northern Mexico will translate into
southern Arizona, with northward moving outflows by this evening
and Sunday. Eventually, we will be back into a low to medium
grade monsoon pattern, by tomorrow or Monday.

We will stay in this pattern through Wednesday or Thursday. At
some point later next week, the low is progged to open up and
move east. This will bring drier air back over the area and
activity will exhibit a downward trend.


.AVIATION...For the 18Z package...VFR conditions expected to prevail
at TAF sites through the next 24 hours. Expect increasing cumulus
with bases 7-10kft agl. A few thunderstorms are possible east of a
KSOW-KRQE line after 20Z today which could produce isolated MVFR
visibility. A slight chance of showers or thunderstorms spreads west
to the KFLG and KINW terminals overnight and into Sunday morning.
Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Most areas of northern Arizona will remain dry
today, with a few thunderstorms possible over eastern Arizona.
Moisture returns to much of northern Arizona on Sunday, and with it
chances of mainly afternoon and evening showers and thunderstorms.

Monday through Wednesday...Thunderstorm chances persist through
the period. Light southwesterly afternoon breezes are expected.






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