Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/01/21
Area Forecast Discussion
National Weather Service Phoenix AZ
500 PM MST Fri Apr 30 2021
.UPDATE...Updated Aviation Discussion..
.SYNOPSIS...
Much warmer temperatures are expected through Sunday as high
pressure builds over the Southwest, with highs potentially
reaching 100 degrees today and Saturday. Temperatures will
moderate somewhat early next week, but stay well above normal
as dry conditions and mostly clear skies prevail. Another warming
trend is expected late next week with 100 degree temperatures
possible yet again.
&&
.DISCUSSION...
Latest objective analysis shows a narrow but strong ridge of high
pressure protruding through the central California coast and into
Nevada. Analysis also reveals H5 heights of 583-590 dm stretching
across the forecast area with the higher heights over southeastern
California. This pattern has led to a rapid warming of the atmospheric
column, as seen in the 48-hr evolution of aircraft soundings. The
warming has reached the surface too with 12 PM temperatures having
reached 90 degrees in Phoenix and many other places today, nearly
7-10 degrees warmer than noon yesterday.
Temperatures will make a run towards 100 degrees for most of the
lower desert this afternoon and again on Saturday. For Phoenix,
the NBM probabilities for reaching 100 degrees is around 20% this
afternoon and at 45% for tomorrow. The first 100 degree day for
Phoenix typically occurs around May 2nd. Temperatures are even warmer
farther west along the Colorado River and southeastern California
due to closer proximity to the high pressure center. Current temps
there are right around 100 degrees.
Ensemble guidance remains consistent pulling a low amplitude shortwave,
currently off the PNW coast, southward along the California coast and
into the Southwest. The first implication of this system will be
increasing cloud coverage Saturday as upper level moisture increases.
If cloud coverage is thick enough, Saturdays temperatures could be
subdued slightly and fall short of the century mark in Phoenix.
Regardless, decreasing heights will ultimately lead to a cool down
into the low to mid 90s Sunday and Monday. A tighter gradient will also
produce breezy conditions this weekend with afternoon and evening gusts
approaching 25-30 mph. Parts of southeastern California that typically
experience stronger winds, like Mountain Springs, could see isolated
gusts of 35-40 mph. Isolated and/or temporary areas of blowing dust
cannot be ruled out.
Rain chances for south-central Arizona appear to be near zero but this
system could advect enough moisture to produce a few showers over
northeastern AZ, with 10-15% chances for an isolated shower surviving
south of the Rim in Gila County Monday. Broad troughing will eventually
be replaced by another Pacific ridge by the middle of next week. The
latest available NAEFS guidance favors H5 heights of 582-588 dm
returning by next Wednesday/Thursday signaling another warming trend.
If Phoenix does not reach 100 degrees by this Saturday, look to
Thursday when the odds of reaching triple digits are around 80%.
&&
.AVIATION...Updated at 0000Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Current light westerly winds are expected to become easterly during
the late evening hours as light sfc pressure gradients allow winds
to primarily follow typical diurnal trends. As far as Saturday is
concerned, morning easterly winds are expected to transition to
southerly cross winds during the late morning/early afternoon hours
before becoming westerly during the late afternoon/evening hours.
Wind speeds on Saturday afternoon to rise into the mid teens with
gusts rising in the low 20`s as a weather disturbance moving into
the Great Basin begins to increase winds aloft over the region.
Mostly clear skies will persist through tonight before SCT-BKN high
clouds aoa 25 kft increase during the day on Saturday.
Southeast California/Southwest Arizona including KIPL and KBLH:
Current light/variable winds at KIPL to become westerly sundowner
winds by mid-evening, with these westerly winds persisting through
the rest of the night and into Saturday morning. WInds at KBLH to
remain light southerly through Saturday morning. A weather
disturbance moving into the Great Basin will increase winds at both
SE CA TAf sites Saturday afternoon, with wind speeds rising into the
upper teens (gusts into the mid-20`s) at KIPL and up into the mid-
20`s (gusts into the mid-30`s) at KBLH. Mostly clear skies will
persist today before SCT-BKN high clouds aoa 25 kft increase
tomorrow morning.
&&
.FIRE WEATHER...
Monday through Friday:
Temperatures will warm every day eventually reaching the upper
90s/low 100s by Wed/Thu. RHs will simultaneously trend downward.
Min RHs will drop from 10-20% Monday to 5-12% by Wednesday and
beyond. Widespread recoveries into the 20-30% range are expected
most nights with slightly higher readings closer to agricultural
centers. Monday could be a bit breezy with gusts nearing 25-30 mph
producing locally elevated fire danger, but for the most part,
winds will follow typical diurnal/terrain driven trends.
&&
.CLIMATE...
.Daily Record Highs...
Phoenix Yuma El Centro
.......... .......... .........
Fri 4/30 102 (1943) 103 (1943) 104 (1965)
Sat 5/1 103 (1985) 106 (1947) 106 (1947)
Sun 5/2 107 (1947) 111 (1947) 113 (1947)
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...AD
AVIATION...Smith/Percha
FIRE WEATHER...AD
CLIMATE...Kuhlman