FXUS65 KPSR 222034
Area Forecast Discussion
National Weather Service Phoenix AZ
Issued by National Weather Service Tucson AZ
134 PM MST Tue May 22 2018
Quiet weather is expected across the area through next week with
near normal temperatures and dry conditions forecast. Some
breeziness is possible late this weekend into early next week as a
disturbance passes through northern Arizona, otherwise tranquil
weather will prevail.
Early afternoon water vapor imagery reveals a slow moving upper
low over southern Nevada, with a dry slot noted across much of
Arizona. While most of the western CONUS is seeing some degree of
cloud cover associated with this low, southern Arizona and
southeast California are virtually cloud-free as of 20Z. This has
allowed temperatures to rise well into the upper 80's across the
lower deserts. Topping out in the low 90's later today seems more
than reasonable based on trends and incoming model data.
Overall a fairly quiet weather week is in store for the region.
The aforementioned low will drift northward on Wednesday, ushering
in weak ridging, drier air, and less wind. This ridge will remain
in place through the end of the week into the first half of the
weekend, resulting in a steady increase in temps. Friday looks to
be the warmest day of the week with highs creeping up right to
around 100 degrees. Just as temps start to warm up, yet another
upper low is forecast to move onshore and through Nevada Saturday
into Sunday. Much like today's low, this one will also remain well
north of the area. If nothing else it will bring some increased
winds and a slight drop in temperatures (highs retreating back
into the mid 90s) for the holiday weekend. As the low departs
early next week, look for temps to once again trend upward with
most blended guidance suggesting a return of the 100 degree temps
by Tuesday of next week.
South-Central Arizona including KPHX, KIWA, and KSDL:
A low pressure system across southern NV will continue to produce
gusty west to southwest winds into the evening hours. For KPHX peak
gusts from the west-southwest could reach 20 kt late into the
early evening hours before subsiding.
Southeast California/Southwest Arizona including KIPL and KBLH:
With a low pressure system just north of the area, winds will
remain southerly at KBLH and westerly at KIPL, with speeds
generally at or below 15 kt.
Friday through Tuesday:
Dry conditions will prevail across the districts through the
holiday weekend with temperatures a couple degrees above normal
Thursday and Friday cooling back near normals over the weekend.
Afternoon minimum humidity levels will mostly fall in a 5-10%
range with generally poor overnight recoveries. Wind speeds will
begin to increase Friday across SE California, then across the
remainder of the districts on Saturday. Wind gusts approaching a
25-30mph range will be possible leading to an elevated fire
danger, particularly on Saturday.
.SPOTTER INFORMATION STATEMENT...
Spotter activation will not be needed.
FXUS65 KTWC 222123
Area Forecast Discussion
National Weather Service Tucson AZ
Issued by National Weather Service Phoenix AZ
223 PM MST Tue May 22 2018
.SYNOPSIS... Dry conditions through the upcoming holiday weekend.
Gusty winds will weaken tonight and should return again this
weekend as a couple of low pressure systems move north of the
area. High temperatures will warm above seasonal normals later
this week before cooling near to slightly below normal for this
An upper level low is currently centered over southern Nevada this
afternoon generating clouds and thunderstorms over much of the
Great Basin. Just to the south, the Desert SW sits under dry
southwesterly flow with PWs around 0.4 inches. In response to this
low pressure system moving to our north, breezy winds have
developed this afternoon with gusts ranging from 20-30 mph across
much of our CWA. Given the dry and breezy conditions, a Red Flag
Warning remains in effect from noon to 7 PM MST today for the
Models are in excellent agreement of rapidly moving this low
pressure circulation into Montana by Wednesday afternoon while
Arizona remains under weak and dry southwesterly flow. Looking
beyong this, heights will gradually build through this work week
warming temperatures a few degrees each day with upper 90s
forecast by Friday. However, this warming trend will come to a
halt on Saturday as yet another upper level low pressure system
approaches our area. Temperature gradients associated with this
approaching low will tighten surface pressure gradients and
bring more breezes to our area come Saturday. Models agree that
modestly cooler air will also begin infiltrating our area come
Saturday and Sunday knocking high temperatures down by a few
degrees each day. Given the dry nature of this system, elevated
fire danger will also be of concern on Saturday.
Models and ensembles are in surprisingly good agreement of
lingering this upper low over our area through at least the
beginning of next week. During this period, temperatures could be
near to even slightly below normal. One caveat is that the
position of this low will really dictate our temperatures in the
extended. Previous model runs have positioned this system further
north continuing the above normal temperatures into the weekend.
However, given the latest model consensus of a more southerly
track we have trended temperatures down for the weekend as
confidence grows in this particular solution.
.AVIATION...Valid through 23/18Z.
Under clear skies, gusty SSW winds will be the main aviation
concern. Gusts nearing 25-30kt will prevail through sunset, then
weaken later this evening. Directional headings this afternoon will
be somewhat more due south than is typical. The usual light and
variable drainage wind will settle in overnight. Aviation discussion
not updated for TAF amendments.
.FIRE WEATHER... A Red Flag Warning is in effect from noon to 7 PM
MST today for the northern portions of Fire Weather Zone 153; or,
more specifically for the Alpine District. The combination of
strong and gusty southwest winds, low relative humidity, and a
very high fire danger will create critical fire conditions.
Beyond this, winds will weaken Wednesday through Friday but
sustained speeds up to 15 mph will still be possible each
afternoon. Another low pressure system will approach our area this
weekend bringing another round of breezy/windy conditions on
Saturday elevating fire danger across our CWA. In general,
humidity will be very low with afternoon minimums near 10 percent
each day. Unfortunately, no precipation is expected through the
Red Flag Warning until 7 PM MST this evening for AZZ153.
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FXUS65 KFGZ 222145
Area Forecast Discussion
National Weather Service Flagstaff AZ
245 PM MST Tue May 22 2018
.SYNOPSIS...An area of low pressure over Nevada today will weaken
and move north over the next several days as higher pressure
builds over Arizona. This will bring a drying and warming trend
with less wind. Increasing winds are expected over the Memorial
Day weekend as another strong area of low pressure moves across
California and Arizona.
.DISCUSSION...The center of the upper low is moving into
southwestern Utah this afternoon. Isolated showers and
thunderstorms are continuing to move northeast across far
northwestern Coconino County. This activity should decrease this
evening and come to an end by dark. The winds across the area will
also weaken this evening.
The low will continue to move northward and weaken on Wednesday
and Thursday as high pressure will builds over Arizona from the
southeast. This will bring a warming and drying trend with less
wind. Daytime temperatures will warm to above normal by Thursday
for much of the Northland. We will still see typical breezy
Another strong area of low pressure is expected to reach the Bay
Area Thursday night and then move into northwestern Arizona by
Sunday morning. This will bring increasing winds on Friday and
stronger winds on Saturday. Sunday will see gusty winds as well.
Moisture looks to be limited with this low as well with only a
slight chance of showers and thunderstorms over the Kaibab Plateau
Please observe all forest closures, fire, and smoking
restrictions across northern Arizona this Holiday Weekend.
Weather conditions will cause rapid spread rates to any fires
that do start.
.AVIATION...For the 00Z package...Expect largely VFR conditions
throughout the next twenty-four hours. ISO-SCT -SHRA/-TSRA near and
NW of a line from KGCN-KPGA will decrease in coverage through the
evening. SSW wind gusts to 25 knots developing along and NE of the
Mogollon Rim Wednesday afternoon. Aviation discussion not updated
for TAF amendments.
.FIRE WEATHER...A Red Flag Warning continues for portions of central
and southern Navajo and Apache counties through 1900 MST.
Afternoon minimum RH values will decrease on Wednesday and
Thursday, with breezy afternoon southwest winds. Temperatures will
return to above normal by Thursday.
Friday through Sunday...Above normal temperatures will continue on
Friday before decreasing to near normal on Saturday and Sunday. A
disturbance moving eastward into the Great Basin is expected to
enhance wind speeds on Saturday as conditions remain dry.
.FGZ WATCHES/WARNINGS/ADVISORIES...Red Flag Warning until 7 PM MST
this evening FOR AZZ113-114-117-140.
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