Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/26/24
Area Forecast Discussion
National Weather Service Phoenix AZ
524 PM MST Thu Jan 25 2024
.UPDATE...
00Z Aviation Discussion.
&&
.SYNOPSIS...
There will be a slight chance of showers across portions of
central Arizona today as a weak area of low pressure slides east
across the state. Lingering moisture will again result in the
potential for patchy dense fog Friday morning. Temperatures will
steadily warm over the next few days with lower desert highs
returning to the seventies this weekend as high pressure builds
over the region.
&&
.DISCUSSION...
Dense fog was observed this morning across the Imperial Valley,
where visibilities dropped to as low as a few hundred feet.
Further east across central Arizona, stratus was more prevalent
but has since dissipated and been replaced by stratocu and altocu
below a weak subsidence inversion evident in the Phoenix ACARS
soundings around 750 mb.
Upstream across northwestern Arizona, latest water vapor imagery
reveals a vort max and associated short-wave trough moving
steadily eastward. Showers have developed ahead of this system,
mainly across northern Arizona. However, latest HREF and other
CAMS suggest the potential for isolated shower activity grazing
portions of the Phoenix Metro Area and areas north later this
afternoon. HREF indicates little potential for significant CAPE,
except closer to the cold core across northwestern Arizona. Model
consensus generally suggests any precipitation that develops will
be quite light and amount to only a few hundredths of an inch.
Moist conditions and light winds will again provide favorable
conditions for fog development Friday morning, particularly across
the East Valley stretching southward into Pinal County. Latest
HREF indicates a 50+ percent chance of visibilities dropping below
a half mile in these areas. Lower, but non-zero probabilities
also extend from Phoenix southwestward down the Gila River Valley.
&&
.PREVIOUS DISCUSSION...
From Friday onward through this weekend, drier conditions and
warming temperatures are expected as high amplitude ridging
builds over the Western CONUS. There will also be some breezy
conditions at times. Especially across southeast CA and southwest
AZ Friday, with 20-30 mph northerly gusts, and in southern AZ
this weekend, but more 15-25 mph from the northeast to east. Lower
desert high temperatures are forecast to return to the 70s this
weekend and continue warming to 5-9 degree above normal in the mid
to upper 70s early next week. No rain is forecasted while the
ridge presides over the region.
By the end of next week and heading into the start of February,
global ensembles are strongly in favor of the ridge sliding
eastward and allowing for troffing over the Pacific to once again
bring about another period of cooler and wetter conditions. The
CPC 8-14 day outlooks reflect this change with a high likelihood
(70-80% chance) of above normal precipitation in the Desert
Southwest during the first week of February. Global ensemble
clusters still show there is plenty of variability in terms of
timing of when the first perturbed waves will bring the next
chances for precipitation. Stay tuned for updates as time gets
closer.
&&
.AVIATION...Updated at 0000Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
A weak upper level disturbance will continue to traverse across N
AZ this evening. Isold showers may pass INVOF KDVT and KSDL over
the next few hrs, but most of the rainfall activity will remain
north of the metro terminals. Ceilings will continue to lift
around 6-8 kft through sunset and clouds are expected to erode
completely by midnight. Our focus then turns to early Friday
morning when fog and low stratus may develop. Hi-Res guidance and
forecast soundings continue to indicate the possibility for
reduced visibilities mainly at KIWA and KPHX between 12Z-18Z.
Probabilities for MVFR to IFR vsbys remain around 20-30% at both
terminals. There is also the potential for a stratus deck to
develop, however confidence remains low and we will keep cigs SCT
for now. Winds will be light and maintain diurnal tendencies
tthrough the forecast period.
California/Southwest Arizona including KIPL and KBLH:
The main aviation concern will be fog development at IPL
overnight, mainly between 09Z-12Z. Therefore, we have introduced
mention of MVFR vsby. Fog is much less likely at BLH and we will
maintain a VFR forecast there. Winds will remain light, aob 8 kts,
with directions favoring a westerly to northwesterly component at
both terminals. Winds are expected to become elevated and gusty at
KBLH early tomorrow afternoon with gusts around 20-25 kts expected.
&&
.FIRE WEATHER...
High low level moisture will keep relative humidity values
relatively high through Friday morning, with minimum RHs around
50-60% this afternoon and overnight recoveries to 85% or higher.
Some spotty showers are expected to develop this afternoon through
this evening, primarily near the Phoenix area and points north and
east. Although, the CWR with these showers will be at or below
10%. There is a non-zero chance for some lightning, but conditions
are not favorable for thunderstorms. Drying conditions through
Friday and warming temperatures will lead to minimum afternoon
RHs falling to 20-30% this weekend that will persist through early
next week. Overnight recoveries will still be good, with most
locations at or above 50-60%. Temperatures will warm back into the
70s for the lower deserts by this weekend. Winds will be light
across all areas today and then turn breezy Friday through this
weekend, with northerly wind gusts up to 20-30 mph across western
districts Friday and 15-25 mph northeasterly to easterly gusts
possible across eastern districts this weekend.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Benedict
AVIATION...Salerno
FIRE WEATHER...Benedict