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Office: PSR

FXUS65 KPSR 222034
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
Issued by National Weather Service Tucson AZ
134 PM MST Tue May 22 2018

.SYNOPSIS...
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.

&&

.DISCUSSION...
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.

&&

.AVIATION...
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.

&&

.FIRE WEATHER...
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.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

DISCUSSION...Leins
AVIATION...JG
FIRE WEATHER...JG/MO



Office: TWC FXUS65 KTWC 222123 AFDTWC 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 weekend. && .DISCUSSION... 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 White Mountains. 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 foreseeable future. && .TWC WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 7 PM MST this evening for AZZ153. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Office: FGZ FXUS65 KFGZ 222145 AFDFGZ 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 afternoon winds. 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 on Sunday. 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. && $$ PUBLIC...MAS AVIATION...AT FIRE WEATHER...AT For Northern Arizona weather information visit weather.gov/flagstaff