Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/07/22
Area Forecast Discussion
National Weather Service Phoenix AZ
539 PM MST Sat Aug 6 2022
.UPDATE...
Updated Aviation section.
&&
.SYNOPSIS...
Limited storm chances will continue for today for Phoenix and the
lower deserts, with better coverage across the higher terrain areas
of eastern and southeastern Arizona. Better chances for more
widespread storm activity is expected beginning Sunday and peaking
in the middle of the week as moisture increases. Along with drier
conditions for today, slightly above normal highs are likely this
afternoon.
&&
An elongated Monsoon ridge axis extends from the central plains SWrd
through S-Cent AZ with SE flow through the mid-upper levels aloft.
GOES WV imagery indicated a slot of drier air over SE AZ approaching
the area while an area of elevated moisture with a weak disturbance
was pushing W out of W-NW NM, where GOES imagery also indicated
scattered CBs. Early afternoon radar showed the main area of
scattered, mostly modest thunderstorms/convection across that same
area and into the E-Cent AZ high terrain. The latest ACARS soundings
show a slightly drier airmass with PW falling to slightly below
1.50" with moderate MUCAPE ~1900 j/kg along with small mid level
caps.
Today`s proximity of the UL ridge axis along with the drier airmass
will support a short warming trend across the region today. Slightly
above normal highs this afternoon will likely reach 106-108 across
the lower deserts with a high of 108 expected for Phoenix. For the
western deserts highs of 107-109 are likely. As a result,
moderate HeatRisk will be the main impact expected today with
thunderstorm activity remaining largely confined to the high
terrain of E, SE and S AZ this afternoon and evening. The HREF
also maintains a potential for gusty thunderstorm outflow winds
this evening, primarily across N Pinal Cty, with a 10-30% chance
of wind gusts >30 kt capable of producing patchy to locally dense
blowing dust there. Late tonight tonight to very early Sun HREF
family members also signal for a secondary outflow and isolated
to scattered showers/convection developing briefly across the
lower deserts both around and W of Phoenix.
Tomorrow evening the HREF/family members and the UAWRF-GFS favor a
gradual increase in moisture and pushing an inverted
trough/disturbance from W-NW NM into E to S-Cent AZ with
convection descending off the E AZ high country into the lower
deserts and Phoenix. Several members like the idea of keeping the
more robust convection concentrated around the outskirts of
Phoenix as the disturbance passes through. Strong and gusty, and
possibly damaging, thunderstorm winds will be the main threat with
these storms, although locally heavy rainfall could also impact
more than just the high terrain and burn scar country.
Going into the week the Grand Ensembles and Clusters agree on
repositioning the high further W into the S Rockies. They are also
in good agreement on a gradual, continual increase in moisture
across the area with the SE flow along the SW flank of the high
through the midweek period. The preferred NBM solution also agrees
and is fairly bullish on elevated POPs and diurnal storm chances
peaking near 40-50% through the midweek period for Phoenix and
the lower deserts, as well as elevated POPs for SW AZ and SE CA.
The preferred WPC QPF is looking for "storm" total QPF through
midweek near 0.20" for the Phoenix metro with higher amounts
featured for the open/lower deserts and high terrain areas.
During this period flash flooding will become the main potential
impact as heat and strong damaging winds largely take a back seat.
Highs are expected to cool to slightly below normal by tomorrow
and remain that way throughout the entire week.
&&
.AVIATION...Updated 0039Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Thunderstorms tonight are expected to remain well removed from the
metro area. West/northwesterly winds will prevail this evening
before beginning to transition to downvalley patterns after
midnight. This is expected to be altered by outflow originating
from storms over Sonora beginning around 09Z-10Z with some minor
south and southwest gustiness for 2-3 hours followed by light and
variable conditions. Some isolated light showers could brush the
metro as well during this time but confidence too low to reflect
in the TAFs. Anticipate an early onset of prevailing westerly
winds (16Z or so) with some minor gustiness (15-20kts) in the
afternoon.
Late Sunday afternoon and evening there is significant potential
for strong outflows to overspread the Valley floor. Early
indications are that there will be an outflow from the northeast
followed quickly by one from the southeast. This could then be
followed by one from the west. In the mix, there could be blowing
dust. The main window of time for this to happen looks to be 23Z-
04Z. There is a 50%-70% chance of gusts >30kts during this time
and 10% chance of exceeding 50kts. Less certain is the occurrence
of thunderstorms over the Valley floor. It is anticipated there
will be at least isolated storms over the Valley floor. But, at
this time, it appears most of the storm activity will tend to
follow the higher terrain to the east and north as well as another
area near and south of I-8 before multiple outflows converge over
western Maricopa County leading to increased storm coverage
there. This scenario is very much subject to change.
Southeast California/Southwest Arizona including KIPL and KBLH:
Thunderstorms tonight are expected to remain well removed from the
TAF sites. Variable winds favoring north/northwesterly directions
will prevail this evening before beginning to transition to
downvalley patterns between 05Z-07Z. Outflow originating from
storms over Sonora is expected to reach the TAF sites in the
10Z-12Z time frame causing some minor gustiness (20-25kts). Some
isolated light showers could brush the TAF sites roughly between
10Z-15Z but confidence too low to reflect in the TAFs. Otherwise,
south/southeast winds are expected to continue through the day.
There is some potential for thunderstorms over the far northern
Baja mountains to affect KIPL with outflow Sunday afternoon but
confidence too low to reflect in the TAF. Likewise for storms over
La Paz County affecting KBLH. There is higher confidence in
outflow from the east moving through late Sunday evening/early
Monday morning.
&&
.FIRE WEATHER...
Dry conditions along with limited storm chances will continue for
today. As moisture increases on Sunday, the chances for more
widespread storm activity increases. Active monsoon storm
conditions are likely to continue across the region through most
of next week as moisture levels remain elevated. MinRHs for today
will range between 15-25% across most areas and will range between
25-40% beginning Sunday and continuing through most of next week.
Generally light winds with some occasional afternoon upslope
gusts can be expected on a daily basis, with the exception of
thunderstorm outflows generating stronger gusts.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Sawtelle
AVIATION...AJ
FIRE WEATHER...Lojero
Area Forecast Discussion
National Weather Service Great Falls MT
826 PM MDT Sat Aug 6 2022
.SYNOPSIS...
Showers and a few thunderstorms are expected today, primarily across
Southwest Montana with more isolated showers further north across
Central Montana. Temperatures across the region have been
significantly cooler today and will slightly increase tomorrow
before hot and dry conditions return throughout the early portion of
next week.
&&
.UPDATE...
Thunderstorms continue to move through the region this evening. Adjusted
wind forecast grids to reflect current wind speed/gust
observations. Then interpolated out a few hours from there. No
further updates will be made, at this time.
- Fogleman
&&
.AVIATION...
801 PM MDT Sat Aug 6 2022 (07/00Z TAF period)
Thunderstorms move across the state, this evening. During periods of
showers and/or thunderstorms, impacted airfields fall into the MVFR
range. Expect to encounter areas of virga. Additionally, mountain
peaks may be obscured. As clouds scatter out during the overnight
hours, reduced visibility in mist/fog is possible. Light aircraft
planning to fly through mountain valleys during the early morning
hours should be particularly cautious. Outside of thunderstorm
activity, winds generally remain light to breezy.
- Fogleman
Winds will be predominately light and variable with exception to
locations in vicinity of showers through the evening. - Pierce
&&
.PREV DISCUSSION...
/ISSUED 801 PM MDT Sat Aug 6 2022/
A positively-tilted trough in Canada extending southwestward into
the Pacific Northwest continues moving eastward overtop the
Northern Rockies. The vort max associated with the aforementioned
trough lies along the northern portions of the Idaho/Montana
border as of 18z, while a weak trough extends even further south
toward the Pacific Ocean. Satellite imagery depicts moisture
associated with monsoonal flow across eastern portions of the
Great Basin and extending northeastward across the Treasure State,
and has led to light precipitation occurring across Southwest and
Central Montana. With the trough axis overhead, temperatures will
remain significantly cooler than the last few days, with most
locations in the lower 70s.
SPC has issued General Thunderstorms across the entire CWA today,
with an excessive rain outlook for portions of Southwest Montana
from the WPC. Showers and thunderstorms are expected across
Southwest and Central Montana this afternoon and early evening.
Primary threat includes flash flooding or debris flows due to heavy
localized rainfall and possible lightning.
As the vort max continues eastward into North Dakota early Sunday,
upper-level ridging rebuilds across western CONUS and continues to
amplify through early next week, reestablishing warmer temperatures
while minimizing precipitation potential. This will exacerbate fire
weather concerns once again as hot and dry conditions persist
through midweek. Wednesday of next week looks to be the warmest day,
with many locations peaking near or just over triple digit
temperatures. By the latter end of next week, the upper-level
ridging will begin to propagate eastward out of the region, opening
the door for monsoonal flow from the southwest to move in,
increasing the potential for some showers. - Pierce
&&
.FIRE WEATHER...
Hot and dry conditions are set to return Monday as a result of an
upper-level ridge building over the western CONUS. Low relative
humidity (<15%) will poor overnight recovery is likely as the
aforementioned ridge propagates overhead and continues to strengthen
during the early portion of the week. Winds will remain generally
light and variable, but the potential for stronger winds and
thunderstorms will be possible during the latter end of the week,
especially as the upper-level ridge begins to shift eastward out of
the region and an onset of monsoonal flow pushes in its wake from
the southwest.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 48 89 52 96 / 60 0 0 0
CTB 47 85 51 91 / 0 0 0 0
HLN 50 90 54 96 / 50 0 0 0
BZN 46 85 48 94 / 40 0 0 0
WYS 39 74 36 81 / 80 0 0 0
DLN 43 82 47 88 / 20 0 0 0
HVR 48 88 55 96 / 10 0 0 0
LWT 46 82 52 93 / 30 10 0 0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
http://www.weather.gov/greatfalls