Scientific Forecaster Discussion
fxus65 kfgz 211032
Area forecast discussion
National Weather Service Flagstaff Arizona
332 am MST Sat Sep 21 2019
Synopsis...this weekend will feature afternoon breezes within a
short-term dry pattern. Temperatures Saturday night could be near
or below freezing for some high country locations. A good chance
of showers and thunderstorms for Monday through Wednesday.
Discussion...temperatures this morning are below freezing in
isolated low-lying areas of the high country. These temperatures
are mainly limited to areas where winds decreased early last
night so radiational cooling was maximized within the inversions.
Some cloud cover is being picked up on infrared satellite imagery
over the White Mountains and should begin to dissipate after
Typical afternoon breezes will persist today, although lighter
than much of the previous work week. A southwesterly flow pattern
will become more northwesterly during this afternoon and evening.
This will continue to bring dry conditions and cold overnight
temperatures into Sunday. Anticipate near or below freezing
temperatures again Sunday morning in similar areas of the high
country as this morning. Remember to cover your plants or bring
A rain event remains in the forecast from early Monday morning
through Wednesday. A low pressure system will drop down from the
Pacific northwest region towards the southwest Sunday afternoon
into the night. Moisture will be transported northward out ahead
of the low and begin to bring rain to portions of central and
northern Arizona by Monday morning. Uncertainty persists in the
exact placement and movement of the tropical moisture. The latest
guidance continues to suggest a 1 - 2" rainfall event over the
span of a few days is likely, but locally higher amounts are
certainly possible. In addition, substantial wind shear and enough
instability could produce conditions conducive for a few strong
or even severe storms.
Small changes in the track of the remnant tropical system could
have an affect on resulting precipitation forecasts, so keep an
eye on the forecast as details become more clear.
Towards the end of the upcoming work week, slight chances for
precipitation remain in the forecast. There is some uncertainty
in these chances for precipitation as this period of the forecast
will be influenced by when the upcoming closed low exits northern
Arizona. An unsettled period within the extended forecast does
look likely though.
Aviation...for the 12z package...look for VFR conditions and
generally light surface winds at 5-15 kts over the next the 24
hours. Aviation discussion not updated for taf amendments.
Fire weather...expect dry conditions and locally breezy afternoon
winds for all of northern Arizona both today and Sunday.
Monday through Wednesday...a strong area of low pressure will
interact with tropical moisture from the south Monday through
Wednesday. This will bring a good chance of showers and
thunderstorms through the period.
Short term...no layers