Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/02/23
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
653 PM CDT Sat Jul 1 2023
.SHORT TERM... (Through Late Sunday Night)
Issued at 222 PM CDT Sat Jul 1 2023
Last nights thunderstorms that went over northern and central
Missouri and central Illinois produced an outflow boundary that at
16Z was located across southeast Missouri and the far southern
portions of Illinois. The outflow boundary has since dissipated,
allowing 75+ dew points to surge north along the Mississippi River,
keeping hot and humid conditions today along and south of the I-70
corridor.
Clouds this morning covered much of the CWA and limited late morning
destabilization. However, clearing has allowed for the atmosphere to
quickly destabilize. Along the clearing boundary, there is a surface-
based CAPE gradient with values in excess of 3000 J/kg, 40kts of 0-
6km bulk shear, and CIN quickly diminishing. An 18:30Z ACARS
sounding at STL are showing surface based CAPE values nearing 3000
J/kg.
To the west of us, ahead of a shortwave trough there is an area of
increased vorticity advection along with an area of surface
convergence that is traversing eastward. As this moves eastward, the
area of surface convergence will interact with the instability and
strong 0-6km bulk shear and will be more than enough to support
strong and severe thunderstorms this afternoon into the evening. The
main threats will be strong and damaging winds and large hail,
however a few brief tornados cannot be ruled out. The location of
the strong to severe thunderstorms will be along and south of the I-
70 corridor, including the St. Louis Metropolitan area where a
CAPE gradient is located. Because of this increased chance for
severe thunderstorms, a Severe Thunderstorm Watch is in effect
until 9PM this evening.
Overnight tonight, the shortwave trough and an upper low will make
its way into the Mid-Mississippi River Valley. This will help
finally push a surface low pressure system and its associated cold
front through the area by the overnight hours. With sufficient lift
from the cold front and increased upward vertical motion, there is
another chance of showers and thunderstorms overnight into tomorrow
morning. Instability overnight will be greatest in the southern
portions of the CWA with guidance indicating over 1500 J/kg. With
this instability and decent mid-level lapse rates, thunderstorms
will have the potential to become strong to severe.
Showers and thunderstorms are forecast to be out of the area by
Sunday afternoon, leaving dry and cooler temperatures to close out
the holiday weekend.
MMG/Carney
.LONG TERM... (Monday through Next Saturday)
Issued at 222 PM CDT Sat Jul 1 2023
Briefly, in the medium range...Monday continues to look like it will
have the least chance for precip out of the next 7 days. Short wave
ridging builds over the Midwest ahead of another upstream short wave
trough, and this should suppress convection across our forecast
area. The aforementioned trough drifts east across the Mid
Mississippi Valley on Tuesday, and though there isn`t any obvious
surface boundary/trigger, there will probably be enough lift to
produce widely scattered showers and thunderstorms. Currently,
CAPE/shear values are such that any storms that form will likely not
be particularly strong/organized, but they could certainly rain on a
few Independence Day Parades. Deterministic guidance is now showing
a stronger/more robust short wave trough moving through the Midwest
Wednesday/Thursday which forces a stronger and better defined cold
front through our area during that time frame. However LREF cluster
analysis still shows variance in timing and amplitude of the trough,
and while the Wednesday/Thursday period still looks most likely for
rain/thunderstorms confidence remains somewhat low on exactly when
the rain will occur, and how strong storms will be/how much rain
will fall. PoPs fall off to chance/slight chance behind the front
on Friday/Saturday.
Carney
&&
.AVIATION... (For the 00z TAFs through 00z Sunday Evening)
Issued at 642 PM CDT Sat Jul 1 2023
Scattered showers and thunderstorms will continue this evening as
an upper level system moves from the Great Plains into Missouri. A
few storms may be capable of producing large hail and gusty winds,
though the storms this evening will likely not be a strong as
storms earlier today. The system will also bring an area of MVFR
ceilings down across much of the area late tonight into early
Sunday morning. There is potential for IFR ceilings, primarily
across northeast Missouri into west central Illinois, but
confidence is too low to mention in the TAFs at this time.
Carney
&&
.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 71 87 71 92 / 30 20 0 10
Quincy 68 83 66 89 / 50 40 5 10
Columbia 67 86 68 92 / 50 10 0 10
Jefferson City 68 89 68 94 / 50 10 0 10
Salem 70 85 66 90 / 70 40 5 10
Farmington 68 89 65 92 / 30 20 5 10
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Phoenix AZ
446 PM MST Sat Jul 1 2023
.UPDATE...Updated 00Z Aviation Discussion...
&&
.SYNOPSIS...
An excessive heat episode will extend through Tuesday with areas
of major heat risk and high temperatures mostly between 111 to
116 degrees. Afternoon temperatures will remain hot through the
latter half of next week as well with widespread moderate heat
risk and afternoon highs more around 109 to 112 degrees. Breezy
conditions can also be expected during the early portions of next
week.
&&
.DISCUSSION...
June 2023 may go down as the coolest June of the 2000s for much
of Arizona and Southern California. Yuma and El Centro official
climate sites had a mean temperature departure from normal of
-4.6F and -4.0F, respectively. Phoenix ended with -2.0F. This
"cool" June was driven by a persistent blocking pattern with a
trough across the west coast. The pattern shifted at the end of
the month and continues now into the first week of July with
strong high pressure centered over the southern half of
California. Upper air sites in California sampled 591-592dm 500mb
heights this morning, which is around the 90th percentile for
this time of year based on sounding climatology. This strong high
is translating to abnormal and excessive heat across the region.
Heat products are in effect throughout California and Arizona
today and continue through Tuesday.
Temperatures so far today in Phoenix are running a couple degrees
warmer than yesterday and recent aircraft soundings out of Phoenix
show a couple degrees of warming throughout the lower troposphere.
This should translate to afternoon highs a few degrees warmer
than yesterday. NBM forecast has highs reaching the 111-115F
range across the lower deserts. Today`s daily record in Phoenix is
115F and NBM supports a 30% chance of reaching the mark. Through
the next couple of days the center of the H5 high is expected to
shift eastward into AZ by Monday. As it stands, Monday is expected
to be the hottest day during the stretch of the Excessive Heat
Warning, which extends through Tuesday. NBM deterministic forecast
highs for Monday range from 112-117F across the lower deserts.
This will translate to several areas of major HeatRisk, including
in the populated areas of Phoenix and the Imperial Valley. Phoenix
and El Centro could both come within a couple degrees of daily
records, 117F and 116F respectively, on Monday. NBM has a 50%
chance of tying or exceeding in Phoenix and a 30% chance in El
Centro. Fortunately, some modest relief from the heat should occur
during the overnight hours with lows anywhere from the mid 70s in
the coolest lower desert rural areas to the mid 80s in the urban
core of Phoenix.
As the high center eventually drifts south southeastward early
next week, setting up somewhere across southeast Arizona, lower
level moisture will increase modestly with the help of southerly
winds off the GoC. This moisture will not help to bring any rain
chances to the area, but it should help to bring temperatures down
2-3 degrees by Tuesday. Eventually, model ensembles favor the
high center drifting a bit farther south across extreme southeast
Arizona into northern portions of Sonora Mexico. This will likely
again bring more of a drying southwesterly flow over the area,
while H5 heights hover somewhere between 591-593dm across much of
the region for the foreseeable future. As a result, the heat dome
is expected to persist through the rest of next week with NBM
forecast highs anywhere from 108-113 degrees from Wednesday
through next weekend. Based on these above normal forecast highs
and forecast lows staying closer to normal readings, an overall
moderate HeatRisk is likely during the period. The extended
outlook still looks very dry through at least July 10, with only
hints at some potential weak moisture starting around July 11-13.
If the high pressure center remains situated to our south or just
to our east like ensembles generally favor through the next two
weeks, rain chances are likely to remain near zero.
Besides the dry conditions and heat, it is worth mentioning there
will be some breezy conditions across the region beginning Sunday
and continuing through Tuesday. Daytime wind gusts up to 20-30 mph
will be possible for many areas and locally higher in some spots.
This could lead to periods of elevated to briefly critical fire
weather conditions. Occurring during a time when sparks will be
flying in celebration could lead to increased fire risk.
&&
.AVIATION...Updated at 2345Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No significant aviation weather concerns expected through the
period under mostly clear skies. Winds will continue to follow a
diurnal pattern, with some occasional gusts through early this
evening approaching 20 kts and again for Sunday afternoon with
some slightly higher gusts ranging between 20-25 kts.
Southeast California/Southwest Arizona including KIPL and KBLH:
No significant aviation weather concerns expected through the
period under clear skies. Wind tendencies will generally be
similar to the past 24 hours through Sunday, although some
gustiness up to 20-25 kts will be possible Sunday afternoon across
KBLH.
&&
.FIRE WEATHER...
Temperatures will warm a couple degrees each day this weekend
resulting in very hot and dry conditions. Highs across the lower
deserts of 112-116F are likely on Sunday and Monday. Winds today
will be fairly light with some afternoon breezes up to 15-20 mph.
Winds will be stronger starting on Sunday, with afternoon gusts of
20-25 mph for most areas and 25-30 mph in high terrain east of
Phoenix. Slightly stronger wind magnitudes are expected Monday and
Tuesday. Minimum relative humidity each afternoon through Monday
will be in the single digits. The very hot temperatures, low RHs
and breezy conditions starting Sunday and again into early next
week will to lead to areas of elevated fire weather conditions. By
Tuesday into Wednesday, moisture will improve slightly allowing,
but this will be most notable in the overnight recoveries, while
MinRHs still remain under 15%. Above normal temperatures will
persist during the latter half of next week, despite cooling
a couple degrees from the even hotter conditions early in the
week.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Tuesday for AZZ530>544-546-
548>551-553>555-559.
CA...Excessive Heat Warning until 8 PM PDT Tuesday for CAZ560>570.
&&
$$
DISCUSSION...Benedict/Kuhlman
AVIATION...Lojero
FIRE WEATHER...Benedict/Kuhlman