Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/30/23
Area Forecast Discussion
National Weather Service Indianapolis IN
1159 PM EDT Sat Jul 29 2023
...Updated Aviation Discussion...
.Forecast Update...
Issued at 951 PM EDT Sat Jul 29 2023
Most of the thunderstorms associated with an MCV have moved
southeast of the forecast area. What lingering showers and storms
there are will weaken/move south of the area within the next few
hours. Canceled the Severe Thunderstorm Watch and adjusted PoPs to
match recent radar trends.
Upped sky cover due to the blowoff from the thunderstorms, but this
will thin out as the night progresses. The northern forecast area
will see the fewest clouds tonight, and with light winds and
lingering low level moisture, expect some patchy fog to form. If
clouds thin fast enough, patchy fog may get farther south than
expected.
Adjusted temperatures based on latest observations, but low
temperatures only needed a few tweaks.
&&
.Short Term...(This evening through Sunday)
Issued at 253 PM EDT Sat Jul 29 2023
A cold front continues to progress south through the forecast area
this afternoon...and was now located around 19Z across our southern
counties. North of the front...lingering stratocu was limiting
sunshine and temp rises while hot and humid conditions continued
over southern portions of central Indiana. Temps in the upper 70s
and lower 80s were common across the northern counties while mid and
upper 80s were present further south. The lower Wabash Valley was
the only spot with temps in the low 90s and heat indices above 100
degrees.
The threat for convection is low and within the short term...focused
over the next several hours over far southern portions of central
Indiana. Current mesoanalysis continues to show an abundance of
inhibition and subsidence left in the wake of the MCS early this
morning with a noted cap off the IND ACARS sounding between 850 and
700mb. The instability axis currently resides from central Missouri
E/SE into the lower Ohio Valley and expect the convective cluster
currently to the west of KSTL to ride along this axis into the
evening. There remains a chance that the lower Wabash Valley will be
clipped by this cluster and will hold onto a low threat for storms
as a result into the evening. That being said...the bulk of the
impacts with the storms will focus to the southwest of the forecast
area through the evening. Will also maintain an isolated risk for
showers and storms along the far southern parts of central Indiana
as the frontal boundary will likely not clear that area for another
few hours.
For the rest of the forecast area...the stratocu over the northern
counties will continue to slowly mix out through the rest of the
afternoon with skies set to become mostly clear this evening as high
pressure builds south. Northerly winds may sporadically gust into
the early evening before dropping off. Some potential for patchy fog
late tonight but the dewpoints will likely drop enough to keep fog
from becoming widespread.
That dewpoint drop will finally bring a respite from the recent few
days of oppressive conditions through the remainder of the weekend.
The zone for convective clusters to track will focus to our
southwest with tranquil weather expected across central Indiana
through Sunday. Expect a diurnal cu field by Sunday afternoon with
continued northerly flow.
Temps...lows will fall back into the 60s across the forecast area
tonight...with potential for lower 60s over northern counties.
Sunday will see seasonable temperatures and lower humidity levels as
low level thermals support mid and upper 80s across the region.
&&
.Long Term...(Sunday night through Saturday)
Issued at 253 PM EDT Sat Jul 29 2023
The synoptic scale pattern which is expected to prevail through the
long range can be described as increasingly amplified. Namely, a
deepening trough over the northeast with an amplifying ridge over
the intermountain west. Our placement relative to each will lead to
predominately northwesterly flow aloft. Additionally, surface high
pressure passing to our north should lead to northerly to
northeasterly flow at the surface through at least Tuesday.
Consequently, a cooler and drier continental air mass will seep in
from Canada. Surface dew points could drop into the 50s and remain
there for some time, which would be a much needed break from the
oppressive heat we have seen.
Moisture convergence across the central Plains is expected to lead
to a band of instability located roughly along the northern edge of
the western ridge (from South Dakota southeast into Missouri).
Given the modest to at times fast flow northwesterly aloft, roughly
parallel with the instability axis...should set the stage for a
"ridge rider" convective regime. This pattern comes into alignment
by early Monday, with most guidance showing multiple rounds of
storms developing well to our west and propagating southeastward.
The main axis of instability / anomalous moisture should remain west
of our CWA through Wednesday, which will allow dry conditions to
persist into Wednesday.
Through the early part of the week, ensemble guidance generally
shows the western ridge slowly building eastward. By Wednesday
morning the ridge is modeled to be centered roughly over Oklahoma.
This gradual eastward motion in turn allows the instability axis to
approach Indiana. Most deterministic guidance has increasing
precipitation chances beginning Wednesday, and continuing into
Friday. A more pronounced trough may pass to our north Thursday into
Friday, dragging a cold front through the region. Consequently, a
more widespread round of organized convection is possible Thursday
or Friday.
While organized convection is possible at times beginning on
Wednesday, refining details at this range is difficult. Coverage and
timing will largely be determined by mesoscale features not
currently resolvable by the global models / ensembles. Here, pattern
recognition is key...and the pattern supports a few rounds of
convection and perhaps an MCS or two later in the week. Whether this
sets up to our west or closer to Indiana will come into greater
clarity as the week progresses.
Looking at non-convective weather, winds, temps, etc...dry
continental air will be present at the beginning of the week, as
mentioned earlier. Relatively light north to northeasterly winds
should veer and gain a southerly component as the surface high
slides eastward. This allows temps to gradually moderate, warming
slightly as the ridge builds in. No heat like recent days is
expected, with highs only in the mid to upper 80s. Dew points will
likewise recover, climbing back into the 60s/near 70.
&&
.Aviation...(06Z TAF Issuance)
Issued at 1159 PM EDT Sat Jul 29 2023
Impacts:
- MVFR fog possible at the smaller airports toward 09z and through
13z, otherwise high confidence in VFR flying conditions with
just passing cirrus
Discussion:
Could see some MVFR and briefly worse fog at the smaller airports
overnight, otherwise high pressure and a dry column will lead to
VFR flying conditions with just passing cirrus with impulses in
NW flow aloft.
Winds will be most NW and N up to 10 knots but very light to calm at
the smaller airports overnight.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...50
Short Term...Ryan
Long Term...Eckhoff
Aviation...MK
Area Forecast Discussion
National Weather Service Phoenix AZ
504 PM MST Sat Jul 29 2023
.UPDATE...Updated 00z Aviation Discussion...
&&
.SYNOPSIS...
High pressure will begin to migrate away from the region over the
weekend as an area of low pressure approaches from Mexico. This will
result in temperatures retreating somewhat closer to normal as
moisture levels increase. Scattered mountain thunderstorms should
become more numerous and descend into lower elevation in an active
monsoon pattern early next week. While strong gusty winds and dense
blowing dust will be the primary weather hazards, some locations
could experience heavy rainfall. This wetter pattern may be short
lived as abnormally hot and dry weather could return during the
latter half of next week.
&&
.DISCUSSION...
Latest mesoanalysis indicates the center of the Monsoon High has
drifted northward towards the Colorado/New Mexico border. This is
producing a light southeasterly steering flow across central
Arizona, generally less than 10 kt. Meanwhile, at the surface,
temperatures and dewpoints are running a few degrees lower than at
this time yesterday. However, the high temperature in Phoenix has
again reached 110 degrees for the 30th straight day.
Latest ACARS sounding from KPHX reveals the thermodynamic profile
is quite similar to yesterday with relatively cool mid-level
temperatures yielding steep lapse rates. Some CIN resides in the
sounding associated with slightly drier air just above the
surface, though a robust outflow boundary should be able to erode
the shallow inhibition. PWATs generally range from 1.3 to 1.6
inches, which along with other convective parameters, should
translate into at least isolated storms across the lower deserts.
There is a discernible signal in the HREF CAMs of an organized
outflow boundary descending out of the higher terrain east of
Phoenix later this afternoon. Severe winds are generally not
expected along the boundary across central Arizona. Higher
probabilities of severe winds will be concentrated across
southeastern Arizona extending northward into Pinal County, though
chances only top out at 10 percent. If storms do materialize in
these areas, areas of blowing dust will also become a concern.
Latest HREF also suggests a 10 percent of cells capable of
producing severe winds near JTNP this afternoon.
Latest NBM also does suggest the possibility of convection across
central Arizona during the late evening and overnight with any
untapped instability and along secondary/tertiary outflow
boundaries.
&&
.PREVIOUS DISCUSSION...
The best combination of synoptic forcing, shear, and thermodynamic
profiles still appears to align across the forecast area during the
Sunday-Monday time frame. Despite the favorable forcing mechanisms
entering the region, boundary layer moisture profiles still present
a forecast challenge and may struggle to attain mixing ratios much
greater than 10 g/kg yielding MLCape not much greater than 1000
J/kg. Nevertheless, high resolution models suggest robust synoptics
forcing scattered storms and numerous outflows Sunday afternoon.
With deep layer effective shear near 30kt and DCape in excess of
1500 J/kg, semi-organized storms near outflow collisions should
yield strong to severe wind gusts and areas of dense blowing dust.
At this time, the preponderance of evidence suggests convergence of
all these features across western Maricopa, Yuma, and La Paz
counties Sunday evening.
The more consolidated activity may shift into SE California Monday
as the easterly wave begins to shear north and become absorbed in
stronger SW flow aloft. Long tracking outflow, persistent convective
complexes, and mesoscale vorticity centers generated Sunday evening
may end up contaminating the convective environment Monday, however
increased flow aloft and larger synoptic features may overcome these
negative factors. Moisture profiles should also be improved with the
prolonged deep southerly flow such that any daytime recovery would
result in renewed instability. Conceptually, one would think the
focus for thunderstorm activity would shift into SE California and
NW Arizona Monday with some measure of subsidence building into
central AZ, however forecast confidence is low given the
uncertainties in the evolution of mesoscale processes.
While some lingering thunderstorm activity may reemerge Tuesday
afternoon into parts of the CWA, the best signal should shift into
NV/UT as a deeper SW flow actually dips into the Southwest. Ensemble
membership remains in good agreement depicting an unusually strong
westerly jet core punching into the Great Basin during the middle of
next week 1) placing the forecast area under midtropospheric
subsidence and warming, and 2) scouring away a good portion of the
moisture just previously pulled into the region such that mixing
ratios fall back to a convectively unsupportive 7 g/kg. As early as
Thursday, NBM POPs essentially disappear from the region as the
Conus pattern begins a retrogressive movement and strong
subtropical ridging sloshes back westward. EPS members appear
strongest with the ridging advertising H5 600dm heights becoming
established over southern AZ next weekend. Even GEFS output
indicates elongated 598dm H5 heights working back into the forecast
area such that forecast confidence is rather good concerning the
return of excessive heat and afternoon readings around 115F next
weekend.
&&
.AVIATION...Updated at 0000Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The main aviation concern through this evening will be the
potential for some gusty outflow winds approaching from the east
from thunderstorm activity across the higher terrain. In the
meantime, through the early evening hours, mainly tranquil
conditions will prevail with westerly winds predominating with
some occasional gusts near 20 kts. Thereafter, between 05-07z, an
outflow boundary is likely to approach from the east resulting in
a wind shift out of the east to southeast with gusts over 20-25
kts. There is a low chance, 10-30%, of gusts exceeding 30 kts.
With the approaching outflow boundary, VCSH are expected across
the terminals. Conditions are expected to improve after 07-08z,
with SCT-BKN mid to high-level cloudiness along with light east to
southeast winds aob 8 kts, with periods of variability, prevailing
through the mid-morning hours. Winds will then prevail out of the
west through the afternoon hours with speeds around 10 kts. There
is a much greater potential for thunderstorm activity (>60%
chance) to directly affect the terminals for Sunday evening.
Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns expected through Sunday afternoon.
Winds will predominate from the southeast at KIPL and from the
south at KBLH with speeds generally around 10 kts. FEW-SCT mid to
high-level clouds are expected through the period.
&&
.FIRE WEATHER...
Well above normal temperatures will cool closer to the seasonal
average through early next week as a short lived wetter weather
pattern settles over the region. Higher terrain storms will become
more numerous and move into lower elevations the next several days
with many areas receiving wetting rainfall, and some isolated heavy
amounts. Erratic gusty winds and abrupt wind shifts will be
significant concerns for any ongoing incidents. Afternoon minimum
humidity levels in a 10-25% range should moisten into a 20-35% range
by early next week. Similarly, fair to good overnight recovery in a
25-50% range will improve to a 35-75% range. However during the
latter half of next week, significantly drier and warmer weather
will likely return to the region.
&&
.CLIMATE...
Record High Temperatures:
PHOENIX YUMA EL CENTRO
July 29 115 (2020) 118 (1878) 115 (1954)
Active Streaks:
PHOENIX
1. Consecutive days of high temperatures 110F or greater: longest
on record at 29 days (previous record: 18 days in June 1974)
2. Consecutive days of no measurable precipitation: 4th longest on
record at 128 days
YUMA
1. Consecutive days of low temperatures 85F or greater: 3rd longest
on record at 18 days
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST this evening for AZZ530-
532-534-537-538-540>544-546-548>551.
CA...Excessive Heat Warning until 8 PM PDT this evening for CAZ562-
563-565>567-569-570.
&&
$$
DISCUSSION...Hirsch
PREVIOUS DISCUSSION...18
AVIATION...Lojero
FIRE WEATHER...18
CLIMATE...Young