Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/07/23
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1029 PM EDT Sun Aug 6 2023
.SYNOPSIS...
Clouds will gradually increase tonight ahead of an approaching
storm system. Rounds of showers and thunderstorms will begin
early Monday morning and continue through Tuesday, with some
locally heavy rainfall possible. Breezy and drier conditions are
expected by Wednesday.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
.UPDATE AS OF 1030 PM...Adjusted PoPs slightly to reflect 00z
guidance which instills a little more confidence in
precipitation timing. This confidence is even more reassured
through location of showers currently depicted on radar as a
line stretching from far-western New York and into central
Pennsylvania. Temperatures were also updated based on latest
obs. Elsewhere, forecast remains consistent.
PREVIOUS DISCUSSION [800 PM]
Most notable adjustments during this update were made to PoPs
to reflect most recent guidance. There still remains a decent
bit of discontinuities in the models as it pertains to shower
start time overnight. However, the RAP and the HRRR generally
agree that a 2-3 AM start is likely. The NAM remains the
outlier, not generating precip until at least 4-5 AM.
Represented a relatively gradual overspread to account for
timing uncertainty, but sided with the RAP and HRRR and began
showers around 2 AM. Of course, it is still possible that the
incoming system could follow a slower track, but with current
MSLP analysis placing the core of the low over the southern
portion of Lake Erie and lowered heights ahead of it stretching
into central NY, odds are the earlier timeframe depicted by the
HRRR and RAP will be realized. Elsewhere, the forecast remains
on track.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
Upper-level trough will slowly push eastward from the Great
Lakes/Ohio Valley region on Monday and across our area on
Tuesday. Initial band of showers will continue to advance
northward Monday morning into the early afternoon hours with a
decrease in activity in its wake. Most model forecast soundings
suggest that low-levels remain rather moist (especially at the
925 hPa level), and the overall low-level wind flow is out of
the southeast. As a result, we may remain in a more stable air
mass with a low-level stratus deck in place for much of Monday.
This would also keep the surface warm front to our south, which
most guidance is suggesting. This would also keep temperatures
on the lower side on Monday and followed suit with highs only in
the mid-60s to mid-70s.
Scattered to numerous showers and thunderstorms will likely
develop during the afternoon and evening hours, especially
across areas in the warm sector (to our south and west). This
activity should occasionally push across the region later in the
afternoon and through the overnight hours. CAMs continue to
struggle with timing of this activity with most members
suggesting additional activity during the late afternoon and
evening with the hi-res NAM holding off activity until the
evening and overnight hours. Will cap pops at the likely range
due to the uncertainty with timing and fine tune as the event
gets closer.
Despite limited instability in place, there could be enough
shear in place for a few stronger thunderstorms later Monday
afternoon into Monday night, especially if the struggling warm
front lifts northward across portions of the area. A marginal
risk for severe thunderstorms remains in place per the latest
outlook from the Storm Prediction Center. We also remain in a
slight risk for excessive rainfall as locally heavy rainfall and
minor flooding problems could occur due in part to precipitable
water values between 1.50 and 1.75 inches (1 to 2 standard
deviations above normal).
Any instability will begin to wane during the day Tuesday as
the upper-level and surface system push across the region.
Additional showers are expected along with a couple of
thunderstorms. Coverage once again is uncertain so will cap pops
in the likely range. Pending on the timing of the cold frontal
passage, a few stronger thunderstorms could occur, especially
for areas south and east of Albany. There could be a few more
breaks in the clouds on Tuesday, so high temperatures look to
rebound into the 70s to lower 80s. Portions of the Adirondacks
look to remain in the upper 60s where more cloud cover and
wrap-around showers are expected.
Precipitation begins to taper off Tuesday night as a westerly
breeze picks up behind the front, but a few showers could linger
through the night with moist, upslope flow in place. Lows will
dip into the mid-40s to mid-50s.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Wednesday will continue to trend drier as weak upper-level
ridging builds across the region, though a few isolated showers
may linger, especially across northern areas. It will be a
rather breezy day with west to northwesterly winds occasionally
gusting between 25 and 35 mph. Highs once again will reach the
lower 70s to lower 80s.
The pattern later in the week through next weekend will consist
of a series of upper-level troughs passing through the flow with
weak ridging in-between. Next trough may arrive around the
Thursday time frame with chances for a few showers and
thunderstorms once again. Friday may turn drier before unsettled
weather returns with the next trough over the weekend. High
temperatures most days will be in the 70s and 80s with lows in
the 50s and 60s.
&&
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Through 00Z Tuesday... VFR conditions will persist this evening and
through much of the overnight, with increasing high/mid level
clouds. Cig heights will lower to MVFR around or shortly after
sunrise, as a warm front approaches from the south/west. Chances
for showers will also increase from SW to NE ahead of the warm
front Monday morning. Will first mention PROB30 for a few hours
at each site, then prevailing showers ranging in onset time from
11Z at KPOU to 14Z at KGFL. As moisture increases and the warm
front still expected to be positioned west of the area, cigs
should lower to IFR levels mainly during the afternoon (except
morning at KPSF). Coverage of showers may become more scattered
during the afternoon.
Winds will be east-southeast around 5 kt or less tonight,
increasing to 5-7 kt on Monday.
Outlook...
Monday Night: High Operational Impact. Breezy. Likely SHRA...TSRA.
Tuesday: High Operational Impact. Likely SHRA...TSRA.
Tuesday Night: Moderate Operational Impact. Breezy. Chance of SHRA.
Wednesday: Moderate Operational Impact. Breezy. Slight Chance of SHRA.
Wednesday Night: Low Operational Impact. Breezy. NO SIG WX.
Thursday: Low Operational Impact. Slight Chance of SHRA.
Thursday Night: Moderate Operational Impact. Chance of SHRA.
Friday: Low Operational Impact. Slight Chance of SHRA...TSRA.
&&
.HYDROLOGY...
Dry weather is expected through this evening. Unsettled
conditions return late tonight and continue through the day
Tuesday as a slow moving system brings multiple rounds of
showers and thunderstorms amid an increasingly moisture-laden
air mass. PWAT`s increase to 1.50 to 1.75 inches or 1 to 2
standard deviations above normal. Rainfall totals from late
tonight through Tuesday night may reach 1-3 inches, as locally
heavy downpours occur at times.
This locally heavy rainfall atop antecedent wet conditions will
likely lead to ponding of water in low lying, urban/poor
drainage areas and could lead to a few instances of flash
flooding.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...KL/Rathbun
NEAR TERM...Gant/Rathbun
SHORT TERM...Rathbun
LONG TERM...Rathbun
AVIATION...JPV
HYDROLOGY...
Area Forecast Discussion
National Weather Service Amarillo TX
624 PM CDT Sun Aug 6 2023
...New AVIATION...
.SHORT TERM ...
(This evening through Monday night)
Issued at 158 PM CDT Sun Aug 6 2023
Summary: Active weather has become more conditional today thanks
to the continue presence of a low stratus deck that formed
overnight. Best chances are now with activity moving off the
Southern Rockies and staying sustained long enough to move into
the Northwestern Panhandles later this evening. Better chances for
more widespread activity are present Monday with a new short-wave
and boundary expected to move in that evening.
As of this afternoon, satellite imagery has been presenting a
low- level stratus deck for a majority of the Panhandles that is
hold over from last night. With this deck present and still
holding, the potential for active weather has become a lot more
conditional with most high resolution models presenting high
amounts of CIN over MLCAPE values no greater than 1000 J/kg for
the Panhandles. The only exception to this agreement has been the
3km NAM, which has suggested that a pocket of MLCAPE greater than
2000 might be present in the Northwest later this evening. Given
this trend, best chances for any activity will have to rely
development from the Southern Rockies that can stay sustained and
travel down to our area. NBM has been entertaining this scenario
with POP hanging around 20 to 30% up in the north, but if the deck
still holds, then we will be seeing more remnants of storms than
anything severe. Regardless, cooler temperatures are expected to
be present today with highs today in the 80s to low 90s.
Better chances for activity look to follow Monday as model
agreement sees a short-wave push off the Rockies that evening and
move down into our area. A boundary will likely follow the wave
and help server as staring point for a majority of the activity
with more potentially following later that night with development
off the Southern Rockies. On the side of severe potential, the 3km
NAM continues to be the most aggressive model with MLCAPE values
running into the 2000 to near 3000 J/kg value range in the western
half of the Panhandles. It is also hinting at good shear in the
late evening hours that could keep our tornado chances non-zero
for the same area. On the other end of the spectrum, however, the
RAP is keeping thing a bit quieter with severe winds being more of
the primary threat with MLCAPE values closer to 1500 J/kg and
DCAPE over 1700 J/kg for the day. Most models tend to favor the
outlook provided by the RAP, but there are some hint that a strong
cluster of storms could form near our southwestern most counties.
As for temperature for the day, the cooler temperatures will look
to stick around a bit longer with afternoon highs in the 80s to
low 90s once again.
Scoleri
&&
.LONG TERM ...
(Tuesday through next Saturday)
Issued at 158 PM CDT Sun Aug 6 2023
Our latest model runs show consistency in our upper level pattern
for the extended. Zonal flow continues from our 500mb trough
across the northern CONUS, while high pressure stays suppressed
to the south. Chances for precipitation are scattered throughout
the week, but they remain slight at best. Model ensemble members
are bringing rounds of shortwaves for the coming days, but the
better moisture and instability looks to remain east of our area.
The position of the trough and the timing of our surface
boundaries will be important factors to consider for our rain
chances moving forward. High temperatures will proceed in the
upper 90`s to lower 100`s range this week. Long range model
guidance unveils a potential peak in high temperatures towards the
latter days of the work week. The NBM has Friday`s high
temperatures increasing to the 100-105 range for places along and
south of the Canadian River Valley. 12Z deterministic models
support this idea with 850mb temperatures between 32 and 33 C for
the Amarillo area.
For the weekend, models are showing signs of another pattern
change. The 500mb high transitions over the Four Corners region,
while the subsequent trough digs into the southern Appalachians.
Northwest steering flow is progged to return and PoPs have been
increased for Saturday and Sunday. Temperatures are expected to
remain slightly above average this weekend, but there is a chance
they decrease due to hints of potential afternoon convection.
Rangel
&&
.AVIATION...
(00Z TAFS)
Issued at 614 PM CDT Sun Aug 6 2023
VFR conditions are expected through this period at this time.
There is a slight chance for a thunderstorm at Dalhart and Guymon
tonight, with a slightly better chance at Guymon, but there is
far too much uncertainty in timing and coverage to include in the
TAF at this time. If a thunderstorm were to happen, the current
thinking is that the earliest time of arrival would be around 04z,
but am leaning toward a later time. An amendment will be issued to
address this if confidence increases.
&&
.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX 65 92 66 98 / 10 10 40 0
Beaver OK 62 85 62 91 / 40 10 50 10
Boise City OK 59 89 58 94 / 20 10 30 0
Borger TX 66 94 66 101 / 20 10 40 10
Boys Ranch TX 65 94 65 99 / 20 10 30 0
Canyon TX 66 92 66 99 / 10 10 40 0
Clarendon TX 69 90 68 99 / 10 10 40 10
Dalhart TX 59 91 59 96 / 20 10 20 0
Guymon OK 61 88 61 92 / 20 10 40 0
Hereford TX 66 96 66 100 / 10 10 30 0
Lipscomb TX 63 88 63 95 / 30 10 50 10
Pampa TX 64 88 64 95 / 20 10 40 10
Shamrock TX 66 89 66 98 / 20 20 40 10
Wellington TX 69 92 68 101 / 10 10 40 10
&&
.AMA WATCHES/WARNINGS/ADVISORIES...
TX...None.
OK...None.
&&
$$
SHORT TERM...11
LONG TERM....55
AVIATION...52
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
1025 PM CDT Sun Aug 6 2023
.UPDATE...
Issued at 1025 PM CDT Sun Aug 6 2023
Smoke continues to stream in across the forecast area, with a very
hazy sunset across western and much of central North Dakota. We
did go ahead and add in mention of patchy smoke across northwest
and into north central North Dakota, with more widespread reduced
visibilities across this area generally in the 5 to 6 mile range.
HRRR smoke model still hasn`t picked up well on this trend, so not
the highest confidence in how long near-surface smoke will linger,
but extended mention of smoke through the day Monday.
Should be a quiet night otherwise, with scattered high clouds
across the area. Lows will be in the 50s.
UPDATE Issued at 636 PM CDT Sun Aug 6 2023
Quiet weather continues early this evening with weak northwest
flow aloft as we`re in between systems. The main concern at the
moment is smoke overspreading much of the forecast area, seen on
visible satellite imagery. Stanley has reported reduced
visibility, although is only at 7 miles and it is the only
station so far to show reduced visibilities. We will be keeping an
eye on this through the evening in case visibility reductions get
more widespread and smoke needs to be added to the gridded
forecast. The latest HRRR smoke model runs are not capturing the
current observations well so primarily going off of what we can
see on satellite. No major changes with this update.
&&
.SHORT TERM...(This Evening through Monday)
Issued at 222 PM CDT Sun Aug 6 2023
A stacked low pressure system is spinning over Iowa early this
afternoon. A deformation band of showers and thunderstorms has set
up from north central Minnesota to northeast South Dakota, cutting
through just the southeast corner of North Dakota. It is unlikely
that any forcing will exist to the north and west of the deformation
band for the remainder of the day, resulting in dry weather for
western and central North Dakota. But a few sprinkles cannot be
ruled from the southwest to north central this afternoon, where
dense cumulus fields have developed. Meanwhile, a plume of smoke
aloft has spread over northwest North Dakota. With no change in
directional flow aloft for the foreseeable future, the smoke aloft
could linger and spread further south and east over the coming days.
Early afternoon temperatures are very pleasant for this time of
year, mainly in the 70s.
As the downstream low continues to drift south and east through
tonight, the Northern Plains will be placed under weak northwest
flow aloft with ridging at the surface. A quiet night is expected,
with lows mainly in the 50s. By early Monday morning, a weak mid
level shortwave meandering across southern Montana could bring some
showers near the southwest corner of the state, but most guidance
keeps measurable rain in southeast Montana and western South Dakota,
at least through the morning. There is greater uncertainty Monday
afternoon when the HRRR and RAP develop thunderstorms along a theta-
e ridge crossing southwest North Dakota from northwest to southeast.
This moisture gradient is much weaker in the NAM and not present at
all in the GFS, and the NBM only brings slight chance PoPs into the
far southwest corner of the state Monday afternoon with less than a
10 percent chance where the HRRR/RAP development is located. If the
theta-e ridge does come to fruition and a few thunderstorms do
develop, they would have access to SBCAPE approaching 2000 J/kg but
with weak mid level lapse rates and effective bulk shear less than
20 kts, which would not be supportive of severe convection. Surface
winds will remain light on Monday, with highs reaching the mid 70s
southwest to mid 80s north central.
.LONG TERM...(Monday Night through Sunday)
Issued at 222 PM CDT Sun Aug 6 2023
The Northern Plains will remain under northwest flow aloft with weak
surface flow heading into Tuesday. A cold front attendant to a
strong upper level low crossing southern Canada could bring showers
and thunderstorms into northern parts of the state Tuesday afternoon
and evening. Some guidance also brings a few showers and storms into
the southwest corner of the state Tuesday afternoon and evening as a
southern stream wave ejects into the Central Plains. There is
uncertainty in the CAPE/shear parameter space, but the overall theme
is for relatively stronger shear to the north and relatively larger
CAPE to the south, though both areas may not see sufficient values
to support severe convection. High temperatures on Tuesday are
forecast to reach around 80 to 85.
The Wednesday through Friday period will be marked by temperatures
trending slightly cooler and increased chances for showers and
thunderstorms as another shortwave ejecting off the Canadian Rockies
quickly dives into the Northern Plains. The highest shower and
thunderstorm chances are centered around late Wednesday night
through Thursday afternoon in association with the most likely
timing of the shortwave passage. It does appear that enough CAPE
(maximum values on the order of 2000 J/kg) and deep layer shear
(around 25 to 35 kts) may be present to support a low end risk of
severe weather on Thursday, which matches output from CSU machine
learning guidance. But this risk is also contingent on several other
factors (timing, cloud cover, etc.) that will remain uncertain until
much closer in time. While north central parts of the state will
experience the cooler temperatures as early as Wednesday, western
and southern North Dakota may remain in the lower to mid 80s for
highs until Friday, though these areas have higher than usual
ensemble spread for this time range. Ensembles then tend to favor an
active northwest flow pattern through the weekend, with temperatures
remaining slightly below normal and low chances for showers and
thunderstorms.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 636 PM CDT Sun Aug 6 2023
Overall VFR conditions expected through the TAF period. Northerly
winds will continue diminishing through the evening, becoming
light and variable overnight and into Monday. Smoke aloft is
spreading across the area, but we did not include reduced
visibility from smoke at any terminal with this update.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Jones
SHORT TERM...Hollan
LONG TERM...Hollan
AVIATION...Jones
Area Forecast Discussion
National Weather Service Caribou ME
956 PM EDT Sun Aug 6 2023
.SYNOPSIS...
A weak high builds in through tonight, then slides offshore
Monday. A storm system approaches from the west Monday night,
then slowly crosses the region from Tuesday into Wednesday. This
storm system then slowly exits into the Maritimes through
Thursday. A warm front lifts through the region Thursday night,
followed by a cold front approaching on Friday.
&&
.NEAR TERM /THROUGH MONDAY/...
950pm Update...
Hard to tell how much smoke is lingering after sunset, but HRRR
smoke continues to keep near-surface smoke at constant levels
and present through the night, so left the forecast as is. Skies
mostly clear this evening with some high clouds beginning to
stream in from the west. Winds are quickly decreasing as the
pressure gradient relaxes. No changes to forecast other than
tweaking to current conditions.
615pm Update...
Areas of smoke over much of Downeast early this evening. This
smoke is from fires way up around James Bay. Smoke is near the
surface and impacting air quality and surface visibility, with
visibilities down to around 5 miles. The smoke plume is fairly
narrow and oriented WNW-ESE, presently centered from Dover-
Foxcroft SE to Bangor, Bar Harbor, and Machias. Webcams show
visibilities anywhere from around 5-9 miles in this area. With
the sun setting and the atmosphere quickly decoupling thanks to
a rapidly diminishing pressure gradient, there is concern that
the smoke will become trapped in the boundary layer. Put in
areas of smoke all night for Downeast. Do think that the smoke
should mostly dissipate after sunrise Monday and left it out of
the forecast for Monday for now.
Another change with this update was to increase sky cover over
Northern Maine for Monday morning. Looks like a weak backdoor
cold front from the north will sneak into Northern Maine just
after sunrise and make it south to around Houlton, with a low
cloud deck behind the front. Also lowered temps a touch in the
north for highs Monday, due to the impact of morning clouds.
Just a couple light showers left over far NE Maine, and this
will quickly dissipate as the sun sets. Some increasing high
clouds from the west tonight.
Previous Discussion... Deep layered ridging builds over the
area from tonight into Monday, with its axis moving to the east
late in the day. Other than possibly some lingering showers
early this evening over far east central areas, it should be dry
due to increasing subsidence under the ridge. This should also
allow for sky conditions to become mainly clear tonight,
followed by increasing high clouds from SW to NE on Monday.
There could be some patches to areas of mainly valley fog
overnight, mainly across the North.
Lows tonight should range from around 50 to the mid 50s, which
is near to slightly below normal. Highs Monday should be from
mid 70s to around 80, except in the mid to upper 60s near the
immediate coast. This is near normal for this time of year.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
Heavy rain event on tap for Tuesday and Tuesday night. Trof will be
carving into the Great Lakes Monday evening. H5 ridge will be
breaking down with cyclogenesis bringing significant moisture
advection up into the region and setting the stage for heavy
rainfall. Isentropic lift brings showers to wrn zones shortly after
00z Tuesday and increases through the overnight. These showers look
to be light initially through 06z in warm advection.
By morning LLJ of 40-50kts will have kicked in, enhancing lift
across the region. GFS looks to be slightly more progressive with
all elements likely because upr level trof is more of an open wave,
whereas EC, NAM and CMC keep it more closed off from the flow. This
combined with coupled jet region over the region along with fgen
forcing gives credence to high rainfall rates and significant
synoptic support.
Surface-based instability looks to be lacking though elevated
instability over the Central Highlands and Downeast will be present
Tuesday afternoon, and possibly across the north during the
overnight hours. Any storms will have the capability of producing
very heavy rainfall Tuesday and Tuesday night. Even where storms
don`t occur heavy rain is expected with PW values approaching 1.80
inches and warm cloud depts > 12kft. Flash flood threat is certainly
on the table for Tuesday into Tuesday night and will continue
mention in the HWO but will hold off on Flood Watch until guidance
can come into better agreement and in range of hires CAMs.
Overall storm total rainfall of over 1 inch expected across the
entire region, with portions of the Central Highlands up into
northern Aroostook looking at potential for 2 inches. In upslope
areas and locations that receive storms cannot rule out localized 3-
4 inch amounts.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
H5 low will be exiting into ern Quebec Wednesday night with showers
lingering across the north. Very brief H5 ridging expected drg the
day Thursday with possible peeks of sun and temps climbing into the
lwr 70s across the north and near 80 over Downeast. Next H5 wave
will be quickly following on its heels with more showers moving in
Thu evening into Friday morning. These will be mainly across the
north as wave gives us a glancing blow. Temps will moderate on
Friday with dry conditions expected on Saturday. Another system will
approach from the west Saturday night in unsettled flow.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
NEAR TERM:
Generally VFR with light winds through Monday. However, three
possible hiccups in the VFR...smoke Downeast tonight, patchy fog
throughout the area tonight, and low ceilings Monday morning in
the north. First, let`s discuss the smoke from fires around
James Bay. There is some smoke Downeast, including BGR and BHB.
So far this afternoon/early evening, visibility has been down to
6 SM but not lower. GNR did have 5 SM earlier, but the smoke has
mostly moved SE of GNR toward BHB and BGR. There is concern as
the sun sets and winds get lighter, than the visibility could
drop below 6 SM and more toward 3-4 SM due to smoke trapped in
the boundary layer. Confidence is low however. Think that smoke
will lift during the day Monday and not impact surface
visibility. Next, let`s discuss the fog. Could be patchy fog
later tonight at any TAF site given the recent rain and lighter
winds, but confidence is low which sites will get any and don`t
think it will be too bad at most sites. Fog lifts shortly after
sunrise Monday. Third, let`s discuss the low clouds in the
north. Backdoor cold front moves into far NE Maine just after
dawn Monday and MVFR ceilings are likely behind the front from
PQI north to CAR and FVE. Think the ceilings will lift to VFR
around midday.
SHORT TERM:
Monday night...MVFR conditions falling to IFR after midnight in
low cigs, fog and rain. ESE 5-15kts gusting to 20kts.
Tuesday-Tuesday night...IFR or lower in locally heavy rain and
tstms. ESE 10-20kts. LLWS at terminals.
Wednesday-Wednesday night...IFR northern terminals, improving to
VFR south Wednesday evening. Variable winds Wednesday becoming
NW 10-20kts in the evening.
Thursday...VFR. NW 10-20kts and gusty.
Thursday night...MVFR or lower. SW 5-10kts.
Friday...Improving to VFR. W 5-15kts.
&&
.MARINE...
NEAR TERM: After some winds up to around 15kt early, the
pressure gradient will relax over the waters tonight and remain
so for Monday. As a result, wind speeds will otherwise be 10 kt
or less and seas 3 ft or less through Monday.
SHORT TERM: Conditions increase to SCA levels Tuesday morning as
winds gust to 25 to 30kts into the nighttime hours. Seas rise
above 5ft, possibly reaching 6 to 8 feet in the evening. Seas
look to remain elevated through Wednesday night before
diminishing.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...Foisy/Maloit
Short Term...Buster
Long Term...Buster
Aviation...Foisy/Maloit/Buster
Marine...Foisy/Maloit/Buster
Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
638 PM CDT Sun Aug 6 2023
.SYNOPSIS...
Issued at 230 PM CDT Sun Aug 6 2023
Severe storms and localized flash flooding are possible into the
evening and overnight hours. Lows tonight should hover in the mid-to-
upper 60s. Showers and cloudy conditions to linger into Monday. More
chances for showers and thunderstorms return by mid week.
Temperatures remain seasonable through the week.
&&
.DISCUSSION...
Issued at 230 PM CDT Sun Aug 6 2023
-------------------[Discussion]-------------------
Today`s main story is the severe weather risk this evening. Models
are trending to agree that the timing of this system should be 4PM
to approximately midnight. There is sufficient moisture in the
atmosphere, but dewpoints aren`t all that impressive. The effective
bulk shear shown on the NAM 3km and HRRR models 12z.6 runs have
values of 40-55 kts. The CAPE values are not all that impressive.
The surface is slightly capped, which the surface heating will be
minimized by the cloud moving overhead. There was a short break in
the clouds between last nights MCV circling to our northeast and
the incoming low pressure system. The MLCAPE shows 1500-2200 J/kg
along and south of a Schuyler Co to Crawford Co line. North of
this line has the higher values of CIN. The storms that develop
will be supported mainly by the high shear values. This is a
classic case of a high shear / low CAPE day in central Illinois.
SPC has the majority of the CWA in a slight risk for severe weather.
Part of the CWA in a 15% hatched area for sig hail. After looking at
the environment and hail parameters. It may be difficult, but not
impossible, to get any sig hail. Lapse rates aren`t supportive of
large hail. The area they have circled with a 5% tor is about where
I believe will be the area of interest this evening for severe
weather. There is a 15% risk for wind. DCAPE values of near 1000
J/kg support that there may be some strong, and potentially
destructive, wind gusts within the storms.
Today has a risk for some flash flooding on top of the severe
threat. The area of interest for any localized flash flooding is
primarily north of I-72, however if there is a cell that is
proficient in rainfall can cause localized flooding south of I-72.
NAM model soundings for several locations in central/southeastern
Illinois show a long, skinny CAPE profile, PWAT values of 1.9 to 2.2
inches, and a deep warm precip process layer. There was sufficient
precipitation yesterday, that there may some issues in the urban
areas of the CWA, especially the northern half of the CWA. The
ground is well saturated. The low-level jet is expected to
strengthen which will push more moisture into central Illinois. If
we get rain rates of greater than 1.5"/hr or 2.5" in 6 hours,
problems may arise for localized areas. WPC has the majority of
Illinois in a slight risk for excessive rainfall.
After today, showers and cloudy conditions linger into Monday as the
surface low finishes moving through the area. Tuesday looks to be
dry before wetter conditions return for the remainder of the week.
Temperatures remain seasonable through the forecast, with highs in
the 80s and lows in the 60s.
Delaney
&&
.AVIATION... (For the 00z TAFs through 00z Monday Evening)
Issued at 638 PM CDT Sun Aug 6 2023
It`s a complex forecast tonight, with a mix of IFR, MVFR, and VFR
ceilings through the evening across the east associated with
multiple waves of storms expected through midnight. The system
currently moving east through central Illinois has the potential to
produce frequent lightning, strong wind gusts, and localized hail.
Overnight tonight, northerly flow behind the surface low will advect
cooler air across a moistened boundary layer to result in areas of
fog (locally dense) and low stratus. Due to the system low tracking
through the area, winds will shift counterclockwise through the
period.
Delaney
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Monday morning for ILZ027>031-036>038.
&&
$$
Area Forecast Discussion
National Weather Service Indianapolis IN
1045 PM EDT Sun Aug 6 2023
...Updated Aviation Discussion...
.Mesoscale Update...
Issued at 916 PM EDT Sun Aug 6 2023
Evolving MCS and evidence of an organized/intensifying cold pool
over central Illinois is moving into a favorable downstream
environment for continued forward propagation. This should
eventually merge with the slower moving discrete cell near Newton,
IL thereby decreasing the hail threat. Strong to locally damaging
wind gusts will accompany the evolving MCS across roughly the
southern half of our area. The northern extent of the threat of more
intense convection and associated wind potential is somewhat in
question and will depend on the pace of returning surface of
richer/deeper lower tropospheric moisture and resultant
destabilization. We don`t think this will occur north of I-70 at
this time, but it could be close. Low-level shear will increase
about the time near-surface buoyancy decreases so the tornado threat
is quite low, but nonzero.
&&
.Forecast Update...
Issued at 702 PM EDT Sun Aug 6 2023
Influence of approaching midlevel shortwave trough is evident in
visible satellite with more vertically-developed cumulus and
mature convection near/north of the warm front into west-central
Illinois. We will need to watch the trend with merging/expanding
cold pools to our west as the magnitude and timing of this process
will dictate the evolution of an MCS that would move into central
Indiana.
We sent a timing graphic to partners and social media with our best
guess of arrival times, and didn`t stray too far from CAMs as they
should have a reasonably good handle in this particular scenario.
The swift midlevel flow (at least relative to this time of year)
should contribute to 35-45-knots effective shear, supporting
downshear propagation around 45-50-knots (assuming organized
fairly strong cold pool evolves). If convection is a little more
scattered and cold pools don`t effectively merge, convection may
struggle to organize into an MCS. This seems like a less likely
alternative to the above though.
Hazards should be limited to strong to locally damaging winds, as
low-level thermodynamic environment isn`t particularly buoyant for
tornadoes and storm mode won`t favor severe hail. Speed of the
MCS relative to the northeastward surge of lower tropospheric
moisture driving destabilization will dictate how far north the
most intense convection gets. There will probably be a slight
favoring of upshear component and thus the southern end of the MCS
may remain most intense.
All other forecast elements look fine at the moment and little
adjustment was needed at this time.
&&
.Short Term...(This evening through Monday)
Issued at 302 PM EDT Sun Aug 6 2023
* Strong to potentially severe storms return this evening into
tonight
* Relatively cool on Monday with more showers
Rest of This Afternoon...
Low pressure across northern Indiana will continue to weaken and
move away from central Indiana. This will allow the break up/mixing
out of the lower clouds to continue slowly from southwest to
northeast. Temperatures will respond to sunshine, with readings in
the 80s southwest to the mid 70s northeast by late afternoon.
Some showers have developed in central Illinois this afternoon in
weak lift ahead of an approaching system. Not sure that they`ll
survive into central Indiana given less instability and being
farther from the lift, but will include a slight chance PoP in the
far west to account for any that make it.
The southwest third of the area will see the most sunshine through
the day, allowing instability to build there. Some storms may
develop late in the afternoon, so will keep the thunder mention very
late this afternoon there.
Tonight...
Thunderstorms will develop late this afternoon and early this
evening in Illinois ahead of a low pressure system. 850mb winds will
increase from the southwest, bringing in moisture and lift. In
addition, the left exit region of a 500mb jet will move into the
area this evening.
Decent instability will have built across southwestern portions of
central Indiana during the afternoon into early evening, with weaker
but still existent instability farther northeast. The storms will
continue to follow the instability and move into central Indiana
from the west starting mid-evening and continuing into the overnight.
Best instability and shear will be across southwest portions of the
area. This will be the most likely area to see any severe storms.
However, with some instability farther northeast, and a warm front
in the same area, severe storms will be possible there as well.
Will continue to watch how things play out. Latest HRRR runs are
showing a potential MCS moving across the area roughly 04-07Z, but
other CAMS are not convinced. At any rate, damaging winds will be
the most likely severe threat. Locally heavy rain will also be
possible.
Will go likely or higher PoPs all areas at some point during the
evening into the early overnight. PoPs will diminish some late
tonight as initial forcing weakens. Lows will be in the mid 60s to
near 70.
Monday...
Central Indiana will remain underneath an upper trough on Monday,
and the surface low will move into northern Indiana. Thus, expect
forcing to ramp back up as the trough and low pressure move in.
Moisture will still be plentiful. Will go with likely PoPs most
areas at some point during the day.
Right now it does not look like an all day rain. Some weak
instability will remain, so some rumbles of thunder cannot be ruled
out.
Skies will be mostly cloudy to cloudy. This plus the rain will keep
temperatures below normal. Most areas should not see 80 degrees.
&&
.Long Term...(Monday night through Sunday)
Issued at 302 PM EDT Sun Aug 6 2023
* Temperatures rise back to seasonal norms in the 80s by midweek
* Chance for thunderstorms Wednesday and then again next weekend
Quasi-zonal flow pattern setting up in the upper levels for much of
next week with multiple waves within the jet stream passing through
Indiana. Upper troughing deepens across Southern Canada by next
weekend placing the Great Lakes region and Indiana back in a more
northwesterly flow pattern. Next chance for thunderstorms arrives
Wednesday and then additional storm chances arrive next weekend as
troughing develops over the region. Expect temperatures closer to
seasonal norms in the 80s for much of the week with the potential
for another cool down by next weekend.
.Tuesday...
After a gloomy, dreary, and potentially unseasonably cool start to
the work week, closer to normal summer-time conditions return on
Tuesday. Surface high pressure becomes centered just southwest of
the region by Tuesday bringing much drier conditions to the region.
Tuesday morning may start out cloudy with patchy fog around as
abundant moisture becomes trapped near the surface due to a
subsidence inversion likely to develop. Slightly elevated winds
around 4-7 kts may keep fog from becoming widespread, but this will
be monitored closely over the next couple days. Bufkit soundings
show much drier air advection in working to raise ceilings allowing
for sun to break through the clouds. Low level ridge axis becomes
centered over Indiana by Tuesday afternoon and evening resulting in
slight warm air advection raising 850mb temperatures to 14-15C.
Surface temperatures are expected to be closer to seasonal norms in
the lower to mid 80s. Temperatures may need to be lowered or raised
a few degrees through based on how fast clearing occurs Tuesday
morning.
.Wednesday Through Saturday...
Agreement is increasing among guidance for the midweek timeframe,
raising confidence in the next chance for storms across Central
Indiana. Southwesterly flow and an incoming low level jet increase
Wednesday into Wednesday night ahead of the next approaching system
brining Gulf moisture back into the region. This pattern supports an
MCS possibly moving into the Ohio Valley with most models depicting
some sort of storm complex moving across Missouri into Kentucky.
Based on guidance`s location of the low level jet and surface low,
best threat for severe weather appears further southwest of the
forecast area, but would not rule out the possibility of Southwest
Indiana getting clipped by the storm complex. Both GFS and EC
ensembles show a sharp NW-SE Instability gradient across South
Central Indiana which further supports the main severe weather
threat further south with the potential for the complex of storms to
ride right along that gradient. Nonetheless, heavy rainfall and
lightning from thunderstorms appears to be the main threat across
much of Central Indiana with the damaging wind threat possible
across the south. Will be able to provide more details about timing,
location, and threats as higher-res guidance picks up on this system
in the coming days and model agreement increases.
Forecast confidence then begins to lessen late week into the
weekend, but generally dry conditions look likely for much of
Thursday and Friday unless the Wednesday system slows more than
currently expected. Another low pressure system will move through
the Great Lakes region during the early weekend with a possible
frontal passage across Central Indiana bringing renewed rain
chances and below normal temperatures once again.
&&
.Aviation...(06Z TAF Issuance)
Issued at 1045 PM EDT Sun Aug 6 2023
* Thunderstorms and associated impacts early tonight
* Showers later tonight but decreasing thunderstorm chances
* Sub-VFR ceilings through at least the first part of Monday
Discussion:
The most intense thunderstorms are staying south of TAF sites
tonight, but some vicinity thunder and occasional lightning is
possible. Convective showers and a few thunderstorms will be
possible through the first part of Monday. In the wake of
thunderstorms, ceilings may be VFR at least temporarily then
decrease to MVFR or IFR during the early morning hours and persist
until afternoon. Periods of variable winds may occur, especially
immediately behind storms where east-southeasterly winds may occur
for a period before veering to southwesterly and eventually
northwesterly during the day Monday. Forecast confidence is
moderate.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale...BRB
Update...BRB
Short Term...50
Long Term...CM
Aviation...BRB
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1145 PM EDT Sun Aug 6 2023
.UPDATE...
Issued at 1145 PM EDT SUN AUG 6 2023
Strong to severe storms are found in an active MCS to the
northwest of eastern Kentucky. The CAMs suggest that this cluster
will ride mainly east through the late night along and north of
the Mountain Parkway. Additional storms will be possible for the
rest of the CWA with some potential for a cold pool to develop and
drive the leading edge of the convection a little more south than
the CAMs believe. For that reason have kept some higher PoPs
further south through our CWA late tonight into dawn. Otherwise,
have also added in the latest obs and trends for the T/Td/Sky
grids. These updates have been sent to the NDFD and web servers
along with a freshening of the zones, SAFs, and HWO.
UPDATE Issued at 750 PM EDT SUN AUG 6 2023
23Z sfc analysis shows high pressure now well off to the east of
Kentucky with broad low pressure dominating the Ohio Valley. This
low is centered over western Illinois and starting to spawn a new
round of convection to the northwest of Kentucky. Locally, the cu
is starting to clear out with the loss of daytime heating and
lack of convection. The instability remains decent over eastern
Kentucky but a trigger for convection is lacking until likely
later tonight as the storms evolving to the northwest move this
way - per CAMs consensus. Currently, temperatures are running in
the upper 70s to lower 80s while dewpoints are still quite
elevated in the low to mid 70s, most places. Winds are relatively
light and primarily from the southwest. Have updated the forecast
mainly with the CAMs ideas for the PoPs and convection later
tonight - moving in around midnight in the northwest and settling
southeast through the late night - remaining strongest for the
I-64 corridor. However, should a cold pool develop could see the
storms remain strong as they drop south - exceeding the CAMs
expectations. Did also include the current obs and trends for the
T/Td/Sky grids. These adjustments have been sent to the NDFD and
web servers.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 248 PM EDT SUN AUG 6 2023
Key Points:
* Another round of showers and storms possible tonight, some of
which could be strong and provide locally heavy rainfall.
* Stormy and unseasonably breezy Monday, with all severe weather
hazards possible- particularly east of I-75 and during the
afternoon and evening hours. Isolated flash flooding with training
storms also possible.
* Trending drier from west to east by periods end, as high pressure
approaches behind the departing system.
The short term period will remain active, with several notable
threats to Eastern Kentucky. Starting aloft, a potent mid/upper
level shortwave will start across the Midwest before lifting north
through the Lower Great Lakes into Monday night. Aside from this
feature, a series of troughs and closed lows are in place across
Canada, while stout and persistent ridging remains across the
Southern High Plains. At the surface, low pressure is depicted along
the borders of SD, NE, and IA early this afternoon, with an
attendant cold front arced southwestward through the Southern
Plains. A secondary low is noted across the Ohio Valley, with a weak
front along the Ohio River. Into tonight, a leading shortwave will
traverse through the Tennessee/Ohio Valley. With the aid of a nosing
anomalously (standardized anomaly of 3 to 4 in accordance with
NAEFS) strong 30-45 kt LLJ and a soggy (PWATs near 90th percentile)
airmass, scattered to numerous showers or storms will again be
possible. CAMs indicate convection upstream (Missouri and Illinois)
will grow upscale through this evening, where an MCS will track
through the Ohio Valley overnight. Hi-Res guidance, has struggled
with the details of this, with the latest data suggesting this
complex mainly along and north of I-64. This is compared to prior
data, which tracked further south and was a bit more robust. With
the NAM and RAP favoring 850mb winds of 35-45 kts across the
Tennessee Valley and Commonwealth, was hesitant to buy too closely
into the northern track. As such, generally broadbrushed Eastern
Kentucky with chance to likely (40-60%) PoPs tonight into Monday
morning, with the best focus across the northern half of the CWA. A
few strong storms, depending on the evolution of convection out of
the Midwest, will be possible with elevated instability of 750-1500
J/kg and fair mid level lapse rates. Strong to damaging wind gusts
and some hail are the primary threats with any taller/more robust
storms, along with locally heavy rainfall.
Convection will generally wane for a time into Monday morning, where
the impending positively tilted upper wave will be across the Upper
Great Lakes to Ohio Valley. A cold front is expected to be across
Western Kentucky, sweeping eastward through the day. With
unseasonably strong wind fields associated with this system: 50-65
kt mid level flow, effective shear of 35-45 kts, and effective SRH
between 200-225 m^2/s^2, severe weather will be a concern Monday.
The biggest uncertainties come with timing and available
instability. Guidance, in large part, has stayed relatively even
kilt to slightly slower with the frontal boundary progressing across
Eastern Kentucky Monday afternoon to evening. With uncertainties in
the extent of potential morning convection and cloud cover, along
with the progression of the approaching frontal boundary, the
east/southeast fairs the best opportunity to materialize the better
paired shear and instability. Given the "spring-like" setup, all
severe weather threats are on the table, with damaging wind gusts
the primary concern, but large hail, and a few tornadoes also being
possible. As of this package, suspect convection will fire up and
become more organized with eastward progression into Monday
afternoon, with discrete or clusters favored early on. As the
boundary propagates further eastward into the late
afternoon/evening, a QLCS will take better shape south and east of
the CWA. Like with any supercell potential (composites of 10 to 12 -
high), locally heavy rainfall is also a concern. Isolated instances
of flash flooding and nuisance high water will be possible,
particularly for locations that see any training thunderstorms. Stay
tuned for further updates, as the finer scale discrepancies/timing
become better resolved in the next 12 to 24 hours.
In addition to the mentioned severe/locally heavy rainfall threats,
Monday will be breezy overall. With a climatologically strong low
and pressure gradient across the area, sustained winds of 10 to 20
mph and gusts of 30-40 mph are possible outside of thunderstorms.
NAM BUFKIT point soundings suggest momentum transfer peaking in the
30-35 kt range, where ensemble probs for greater than 40 mph range
from 20-40% in the east/southeast. Winds will slacken into the
evening/overnight as the low and associated trough axis pull out of
the area. Showers and storms will taper off from west to east
through the end of the period as well, though low clouds likely
stick around into Tuesday morning on west/northwest flow.
.LONG TERM...(Tuesday through Sunday)
Issued at 248 PM EDT SUN AUG 6 2023
A cooler and drier air mass filters in on northwest flow for
Tuesday. However, sufficient moisture and forcing (with the axis of
the shortwave trough) will linger on Tuesday, rejuvenating at least
spotty convection primarily east of I-75. Behind the shortwave,
rising heights will attend surface high pressure building across the
Central Appalachian on Tuesday evening/night, finally ending any
leftover shower activity.
The next shortwave trough ejects off the Northern Rockies Tuesday
night and Wednesday. Return flow ahead of this trough will bring
increasing moisture back to the Ohio Valley on Wednesday. This
system will also foster a wave of low pressure riding along the
quasi-stationary boundary to our south, bringing periods of rain to
the Commonwealth from Wednesday night through Thursday night. Drier
weather briefly returns Thursday night into the first half of
Friday. Another cold front may impact eastern Kentucky Friday Night
or Saturday. However, models disagree on the strength of the front
and the extent/intensity of any associated precipitation.
Temperatures in the long-term will largely remain on the cool side
of average. Highs are forecast to peak in the upper 70s to around 80
degrees on Tuesday, warming back into the lower to middle 80s on
Wednesday. Maximum temperatures then retreat back into the 70s on
Thursday as we stay on the cool, rainy side of a passing wave of low
pressure. Forecast highs return to lower and mid 80s on Friday and
Saturday. Nighttime lows are forecast to range through the 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 825 PM EDT SUN AUG 6 2023
Per CAMs and radar trends, expect a shot of convection between
midnight and 6 am, where decreasing ceilings with lower clouds
affect the terminals from northwest to southeast. However, given
uncertainties in the spatial and temporal extent of convection
through the night, have gone with lower ceilings but did stay
within the thresholds of VFR. Dips to the MVFR or lower category
cannot be ruled out with any heavier showers or storms near or
atop any particular airport. A relative brief lull in convection
is then possible Monday morning, before an approaching low
pressure system and cold front bring a renewed threat from late
morning and through the end of the period. With a stronger
pressure gradient across the area tomorrow, winds will be breezy
out of the southwest. Sustained winds of 10 to 15 kts and gusts
between 20 and 30 kts are possible outside of any thunderstorms.
Winds through early Monday morning will generally average less
than 10 kts out of the south to southwest.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GREIF
SHORT TERM...BB
LONG TERM...GEERTSON/CMC
AVIATION...BB/GREIF
Area Forecast Discussion
National Weather Service Louisville KY
940 PM EDT Sun Aug 6 2023
...Tornado Watch in Effect for Portions of the Region...
.Forecast Update...
Issued at 939 PM EDT Sun Aug 6 2023
After coordinating with surrounding WFOs and SPC, Tornado Watch
#598 has been issued for portions of the region, primarily
along/north of the I-64 corridor and along/west of the I-65
corridor. The greater tornado threat will likely be in areas north
and west of the CWA, but given some low-end potential for a spin-
up in our neck of the woods, the decision was made to go with a
tornado vs severe t-storm watch.
Issued at 916 PM EDT Sun Aug 6 2023
Strong to severe storms have developed across portions of Missouri
and Illinois this evening ahead of a frontal boundary. Environment
ahead of the storms features ample shear and instability for
organized convection to persist, including that of supercellular
storms, though its likely that the upstream activity will likely
congeal into a line (or broken lines) dominated by cold-pool
processes.
Current radar and model trends suggest this activity will be
approaching our southern Indiana counties (Dubois, Orange,
Washington, Scott) closer to 11pm or midnight EDT before spreading
eastward the remainder of the overnight hours. Confidence in the
longevity of severe potential overnight in our region remains low,
but feel fairly confident that areas west of I-65 and north of I-64
will have at least a few strong/severe storms with a decreasing
trend in severe potential as the activity advances eastward. The
bulk of the storm activity will likely stay along and north of the I-
64 corridor.
Main severe threat going into the overnight hours will be the
potential for damaging winds, though hail will be possible in more
discrete storms. The tornado threat is low with a subtle surface
inversion inhibiting tornadogenesis processes, but non-zero if a
strong mesovortex develops within a bowing structure or if discrete
supercells with strong low level mesocyclones develop ahead of the
main convective line.
&&
.Short Term...(This evening through Monday)
Issued at 319 PM EDT Sun Aug 6 2023
...RISK OF SEVERE WEATHER TONIGHT ACROSS SOUTHERN INDIANA AND
PORTIONS OF NORTHERN KENTUCKY...
========================================
Near Term Now through 800 PM EDT
Risks : Isolated Storms in the west
Confidence: Medium-High
========================================
Afternoon satellite imagery shows low clouds continuing to scour out
into an afternoon cumulus field. With a bit more insolation,
temperatures have warmed into the lower-mid 80s across the region
with some upper 80s across far southwest KY. For the remainder of
the afternoon, most areas should remain generally dry. Can`t rule
out a stray thunderstorm to pop up across the region. There isn`t a
real particular area of forcing that would suggest a higher PoP over
a certain area, though some models suggest some convection could
fire across southern KY in the next few hours. Recent satellite
imagery does show some vertical Cu development in the Hopkinsville
area. For now, plan on keeping the PoPs at 13% or less on coverage.
Breezy southwest winds will be seen across the region this
afternoon, but these winds should simmer down in the 700-800 PM time
frame. Temps should top out in the low-mid 80s before settling down
into the upper 70s to around 80 by sunset.
========================================
Tonight 800 PM through 800 AM EDT
Risks : Strong/Severe Storms w/
Damaging winds/heavy rainfall
Confidence: Medium
========================================
Moving into tonight, convection should be in progress across
portions of IA/MO/IL. This activity is being forced by a fairly
potent mid-level wave that will push through the Ohio Valley. Ahead
of this feature overnight will be a southwesterly low-level jet axis
pushing into the lower Ohio and TN Valleys. Models vary at the
strength of this jet axis, but 30-35 kts seems to be a good multi-
model consensus here. Plenty of moisture will be available with
PWATs running around the 90 percentile. Upstream multi-cellular and
supercellular convection (across MO/IL) is likely to grow upscale
into an MCS and this feature will track eastward across the Ohio
Valley. Forecast confidence on the track of this is a bit uncertain
given the run to run variations of the CAMs. Initial CAMs from
early this morning had this MCS going through much of KY, but the
trend in the runs has been further north (mainly along and north of
the I-64 corridor). However, given that the LLJ structure will be
in swing across KY/TN, I am somewhat hesitant to believe that the
convection would be that far north, such as what the HRRR suggests.
As of this writing, I think the best chances of storms will likely
be along and north of the WK/BG Parkways. For this forecast, will
keep a slight chance of PoPs south of the Parkways, and then go with
a 30-50% PoP in the area between the Parkways and Ohio River, with
likely PoPs north of the river. With the storms expected to arrive
later tonight, not overly confident in whether these storms will
be surface based. Most model soundings from across the region show
the nocturnal PBL inversion in place by the time storms arrive, but
we`ll have some elevated instability to work with. In this type of
set up, damaging winds, heavy rainfall, and lightning would be the
main severe weather threats. Given that low-mid level lapse rates
will be decent, can`t rule out some hail with this activity,
especially in the stronger cores. Overnight lows look to be in the
upper 60s to the lower 70s.
========================================
Monday 800 AM through 800 PM EDT
Risks : Strong/Severe storms east
Confidence: Medium
========================================
Overnight convection may still be in progress across portions of SE
IN and the Bluegrass region of central KY Monday morning. Surface
cold front is expected to be moving into western KY during the
morning hours and looks to cross the I-65 corridor around lunchtime.
We may have some extensive stratus in the morning in the wake of the
overnight convection. Depending on the stratus, that may hold off
some heating across much of the region. However, this stratus may
mix out and we should be able to get some additional heating in the
afternoon east of I-65. With the front crossing into this
possibility destabilizing atmosphere, a refiring of storms along the
front across central/eastern KY will be possible in the afternoon.
Main threats here would be damaging winds and perhaps some large
hail with any taller storms. Overall progression of the line should
limit residence time of the storms resulting in a low threat of
flash flooding. However, any training of storms could lead to some
isolated flood issues in spots. Highs on the day will vary from
west to east, with readings in the upper 70s to around 80 in the
west, and lower-mid 80s in the east, prior to the front pushing
through the region.
.Long Term...(Monday night through Sunday)
Issued at 300 PM EDT Sun Aug 6 2023
We`ll be in a post-frontal regime by Monday night, with the primary
sfc low spinning off to the Northeast. Drier conditions will be the
story for Monday night into Tuesday as low-amplitude ridging moves
over the Ohio Valley, and we get a weak sfc high across our area.
Tuesday appears to be a fairly nice day, with partly sunny skycover
and temperatures in the low to mid 80s. By Tuesday night, conditions
will be quiet here, but a potent shortwave will be swinging through
the Rockies, ultimately resulting in sfc lee cyclogenesis, and our
next weather feature.
We`ll need to keep eyes on the Wednesday-Thursday time frame as that
shortwave swings through the central Plains. The GFS has been keen
on a MCS feature driving through central Kentucky by Wednesday late
afternoon/evening for several runs now, though other global
deterministic solutions differ a bit on timing. Regardless of the
timing discrepancies right now, there is a fairly good agreement of
a signal for the middle of the week. General consensus is to see
convection initiate over Kansas/Nebraska Tuesday night, push through
Missouri and central Illinois, and eventually dive into central
Kentucky by Wednesday evening/night. Forecast soundings for this
wave indicate strong instability paired with a saturated airmass,
and elevated DCAPEs to promote a damaging wind threat. Showers may
linger into Thursday, though should see a brief drying period by
Thursday night.
For Friday, an upper low will swing across the Great Lakes, driving
a vorticity lobe over the lower Ohio Valley. This will likely lead
to developing some isolated to scattered showers and storms to close
out the work week. Additional rounds of showers and storms will be
possible into the weekend as the upper low gradually makes its way
east of the Ohio Valley.
&&
.Aviation...(00Z TAF Issuance)
Issued at 701 PM EDT Sun Aug 6 2023
Showers and storms have stared to fire off across portions of IL and
MO this evening, and these will gradually push eastward into the
overnight hours and likely grow in coverage/area. Appears highest
likelihood for storms will be along and north of the I-64 corridor,
and areas near the TN border may stay dry for the duration of the
night. Any TAF site that is impacted by a storm will likely see
reduced cigs/vis, and at the onset, brief gusty winds out of the
west or northwest.
Stratus will gradually build in behind the showers and storms
tomorrow morning ahead of a frontal boundary. Could see some brief
MVFR cigs for a few hours before lifting to VFR. Additional storms
may fire off across eastern portions of the region by mid to late
morning, mainly impacting the LEX terminal.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...DM
Short Term...MJ
Long Term....CJP
Aviation...DM
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
953 PM CDT Sun Aug 6 2023
...New UPDATE...
.UPDATE...
Issued at 953 PM CDT Sun Aug 6 2023
Midevening GOES water vapor imagery shows an upper low centered
over eastern IA, with a lead shortwave / negatively-tilted trough
extension ejecting across south central IL. This shortwave will
lift through the Ohio River Valley overnight, while the main upper
trough lifts into eastern IL. The net effect for the Midsouth
will be slow but steady midlevel height falls. Scattered
thunderstorms are expected to develop over northeast AR late this
evening/early overnight, along the southern flank of a 100KT
250mb speed max entering the Ozarks. At midevening, KLZK VAD wind
profiler shows low level warm advection is underway, while GOES IR
imagery and regional METARs shows scattered 6000ft clouds developing
over northern AR.
The 00Z HRRR depicts a plume of 7C/km midlevel lapse rates edging
in to eastern AR overnight. If storms can grow sufficiently under
the aid of the upper jet, isolated instances of large hail will
be possible from northeast AR through the MO bootheel, into
northwest TN. Elevated CAPE of 1000-1500 J/kg will be accompanied
by effective bulk shear around 40kt, supportive of this marginal
hail threat. Damaging wind threat may be limited by a relatively
stable boundary layer. 00Z HRRR dissipates most of the storms by
sunrise, as 925mb winds veer to the northwest. Next round will
likely occur south of I-40 Monday morning, aided by surface
heating along a weak low level boundary.
Forecast was recently updated with minor adjustments to hourly
PoPs, based on 00Z short term blends. No other changes needed at
this time.
PWB
&&
.SYNOPSIS...
Issued at 241 PM CDT Sun Aug 6 2023
A Heat Advisory remains in effect for much of north Mississippi
through 8PM this evening. Hot and humid conditions will continue
across mainly north Mississippi for the next several days. A cold
front is expected to slowly move in tonight, increasing rain
chances through tomorrow night. Another cold front should move in
Wednesday evening, bringing a more widespread chance of severe
weather and cooler temperatures behind the front for the weekend.
&&
.DISCUSSION...
(This evening through next Saturday)
Issued at 241 PM CDT Sun Aug 6 2023
The outflows and cirrus shields from today`s convection may
drastically limit the amount of heating this afternoon, which has
warranted some minor tweaks to heat headlines. The southern two
tiers of counties are still in a Heat Advisory given the latest
heat index observations coming in at 105-109, but a few counties
have been removed since the latest update. It`s also worth noting
that from here on out, confidence in Heat Advisory criteria
continuing to be met for the remainder of the day is quite low.
Tomorrow`s heat indices are still too uncertain to make any
headline decisions with the afternoon forecast package.
A second round of convection associated with a completely separate
system is on the table for the overnight period. A larger, more
synoptically forced system looks to materialize late tonight over
central Illinois. Our severe threat comes from the trailing cold
front lagging behind this system. The southernmost extent of the
strongest convection is still a bit of a question mark as the front
sinks south and eventually stalls out. We may see a few strong to
severe thunderstorms clip the northern tier of counties overnight,
most likely after midnight through about 6AM Monday. We are located
in an area of upper-level divergence with MLCAPE on the order of
1500-2000 J/KG, PWATs around 2 inches, and effective bulk shear
around 25-35 kts. This environment overnight could support
damaging winds and heavy rainfall, though confidence is much lower
for the overnight period.
Looking into next week, a fairly potent upper trough looks to dig
down through the Ozarks on Wednesday evening. For what it`s worth,
the timing of this next system has been gradually shifting 3-6 hours
later with each subsequent model run. Regardless, anomalous moisture
and ample diurnally driven instability will likely spark at least a
few strong to severe thunderstorms across the Mid-South some time
Wednesday evening with the help of this synoptic forcing. As far as
the extended forecast, northwest flow aloft remains firmly in place
through next weekend. This long term forecast is essentially status
quo with the caveat of ever-present impacts from any potential MCSs
or shortwaves ejecting from the Plains throughout the week and
weekend.
CAD
&&
.AVIATION...
(00Z TAFS)
Issued at 600 PM CDT Sun Aug 6 2023
VFR conditions are expected to prevail through the period.
Isolated development along a warm front off to the west is possible
late tonight. CAMs are all over the place this, but there is some
consistency between medium range models. A few storms may fire up
near midnight, but direct impacts to JBR and MKL has a low
probability, so VCTS was kept at those two sites.
More widespread coverage is anticipated tomorrow morning as a
cold front moves across the region. VCTS and gusty winds is
expected at all sites. There may be periods of TSRA and MVFR
conditions, but low confidence on timing warranted any TEMPOs or
PROB30s.
DNM
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
PUBLIC FORECAST...CAD
AVIATION...DNM
Area Forecast Discussion
National Weather Service Morristown TN
929 PM EDT Sun Aug 6 2023
...New UPDATE...
.UPDATE...
Issued at 920 PM EDT Sun Aug 6 2023
Forecast on track this evening with no big changes. Other than an
isolated shower/storm overnight, most will stay dry. Made some
minor adjustments to temps and dewpoints to match up with latest
obs. Biggest overnight impact will be patchy fog, especially
across areas that received rainfall earlier today. Otherwise, All
eyes remain focused on tomorrow`s potential for strong to severe
storms.
&&
.SHORT TERM...
(This evening through Monday)
Issued at 235 PM EDT Sun Aug 6 2023
Key Messages:
1. Chance of showers and thunderstorms this evening associated
with a weak shortwave.
2. Severe thunderstorms expected on Monday associated with an
anomalously intense upper-level shortwave trough.
Discussion:
A weak shortwave is noted this afternoon in WV imagery across
northern Mississippi and Alabama. This will move quickly eastward
and result in a low risk of showers and thunderstorms across our
southern zones this evening. This shortwave will move east of our
area after midnight with lower PoPs towards Monday morning.
On Monday, there are some major questions about the overall severe
weather probabilities across our forecast area. An unseasonably
strong upper-level 300mb jet will shift eastward and setup across
the Tennessee Valley through the Central Appalachians placing the
Southern Appalachians within the right-entrance region for upper-
divergence. An intense 500 mb shortwave will move eastward across
the Tennessee and Ohio River Valleys during the day with strong
DPVA and height falls across our region, especially across
northern East Tennessee through southwest Virginia. In response
to the strong upper-level jet, the 850mb LLJ will intensify
across the Tennessee Valley with winds of around 40 kt expected.
NAEFS forecast anomalies show the 850/700/500 mb winds all at the
max compared to climatology for this time of year. This is an
anomalously intense shortwave and synoptic system which is
resulting in unseasonably strong shear values. The RAP is showing
forecast low-level effective inflow shear up to 30 to 40 kt on
Monday afternoon with effective bulk shear about 40 to 50 kt. This
will support supercell and multicell convective modes.
The big question will be the level of instability. How much
overnight convection do we have? How widespread is convective
debris cloud cover on Monday morning? These are important
questions when calculating the amount of instability available for
severe convection on Monday afternoon. At this time, CAMs are
trending drier on Monday morning with MLCAPE of around 2000 to
2500 J/kg. Large values of instability would result in a
thermodynamic and kinematic environment favorable to severe
thunderstorms with damaging winds, localized hail, and a low
chance for tornadoes. The main tornado risk will be to the northeast
of our forecast area in closer proximity to the surface low and
warm front. PW values between 1.9 and 2.1 inches across our
forecast area will also result in heavy rain rates and some
localized flooding issues where any training occurs. Looking at
previous similar events based on this synoptic setup, CIPS analog
guidance also paints relatively high percentages for severe
weather reports, mainly damaging winds, across much of northern
East Tennessee, the Southern Appalachians, and northeastward
through the Mid- Atlantic.
The main point is that this severe weather forecast is highly
conditional and will depend on the amount of morning convection
and cloud cover present on Monday morning. Still, the anomalous
nature of this system is intriguing and bears paying close
attention to tomorrow.
&&
.LONG TERM...
(Monday night through next Sunday)
Issued at 235 PM EDT Sun Aug 6 2023
Key Message:
Another round of widespread thunderstorms will move into the region
late Wednesday into Thursday. But less certain on when storms will
exit the region.
Discussion:
By late monday night the front will have pushed east of the
Appalachian Mountains leaving most locations dry as we head into
Tuesday. There is a chance for some lingering light to moderate
showers across northeast Tennessee and southwest Virginia into
Tuesday from orographic lift with some wrap around moisture from the
Great Lakes. Coverage of any storms is expected to be limited as
moisture will be limited throughout most of the atmosphere with the
westerly to northwesterly flow.
Quasi-zonal flow will then set up for a few days with slight chances
of isolated thunderstorms in the afternoon during the peak heating.
Shower and thunderstorm chances increase by around Wednesday into
Thursday as another shortwave zips through the region. Long range
models have generally trended a bit faster with the onset of the
convection, with the latest runs pointing more towards a Wednesday
night arrival. Depending on the timing of the convection the
forecast soundings indicate there could be enough forcing to see
strong thunderstorms. During the second half of the week a few
weaker systems will move through the Great Lakes region and try to
push through a frontal boundary...However there are indications that
this boundary could get stalled out somewhere in the Ohio/Tennessee
Valleys through the weekend. If this solution verifies the boundary
would be the ideal location for multiple rounds of storms and cloudy
weather. However this is still several days out with a couple of
stronger systems between us and the upcoming weekend, so expect
models to likely struggle to handle this scenario until we get
closer to the weekend.
&&
.AVIATION...
(00Z TAFS)
Issued at 747 PM EDT Sun Aug 6 2023
TEMPO MVFR in at TYS for the next hour, otherwise VFR conditions
at all sites through the night. Except for MVFR conditions at TRI
due to early morning fog. Then, increasing chances for strong to
severe storms Monday afternoon, affecting all sites. Winds will be
breezy out ahead of the storms and gusting to 25 kts from out of
the southwest.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 73 92 68 86 / 50 80 40 10
Knoxville McGhee Tyson Airport, TN 73 88 68 83 / 30 90 40 0
Oak Ridge, TN 71 87 67 83 / 40 90 40 10
Tri Cities Airport, TN 69 85 66 79 / 40 80 60 20
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...
AVIATION...
Area Forecast Discussion
National Weather Service Nashville TN
930 PM CDT Sun Aug 6 2023
...New UPDATE...
.UPDATE...
Issued at 930 PM CDT Sun Aug 6 2023
We ended up dodging most of the thunderstorms today with them
remaining just to our south over AL. Overall we will remain dry
into the overnight and we should see some clearing for a time but
clouds will fill back in quickly. This will keep fog chances low
tonight. A short wave will be pushing out of the Plains into the
OH Valley tonight into tomorrow. An MCS with this short wave is
developing over IL and is expected to remain to our north
overnight. There is also a cold front over MO stretching south
into AR. This front will push east tonight and enter the western
portion of our area by daybreak. Scattered thunderstorms will
develop along this front and will start to increase in coverage
along this front mid to late morning as it pushes east of I-65.
Bulk shear tomorrow will be enough for some more organized
updrafts and we will see plenty of CAPE by the afternoon over the
eastern portion of the area. Wind is going to be the main threat
with thunderstorms but there is plenty of CAPE in the hail growth
zone for some large hail too. Heavy rain can also be expected with
thunderstorms but storm motion will be pretty quick and the flooding
risk is low.
&&
.SHORT TERM...
(This afternoon through Tuesday Night)
Issued at 220 PM CDT Sun Aug 6 2023
No activity to speak of across the mid state this early afternoon.
The earlier sounding indicated convective temps of around 89F.
Latest temperatures are generally in the mid to near 90. Thus, still
expecting some development to commence over the next couple of
hours. Hrrr leans toward southern middle TN as the better coverage
area. Instabilities will be sufficient enough whereby a few storms
could go strong to severe with damaging winds as the primary threat.
This threat will be primarily for the mid afternoon into the early
evening hours for our southern counties where a severe thunderstorm
watch is now in effect until 8 pm cdt.
Moving on, the potential for mcs development exists for the
overnight. Although, model confidence is very low with this
scenario. Nevertheless, instability parameters seem to be in support
of strong to severe activity overnight. The reason for the low
confidence appears to be due to the lack of organization in regard
to the frontal boundary. N-S extension will remain weak until Monday
morning. At that time, the next chance of severe seems to be late
morning into the afternoon across our east. SPC does have an
enhanced risk across MRX`s area with a slight for us. 18Z
instability levels are quite impressive with -9C LI values, capes of
close to 3000 j/kg, 850 mb speeds of 35 kts and reasonable
organization. Those capes are impressive through the -10C to -30C
zone as well so perhaps some hail along with the damaging wind
potential.
Drier air will finally win out for Tuesday into Tuesday night. So,
we can basically put an end to the pops at that time. Although, the
boundary to our south may force the builder into some low pops for
our southern areas.
For the near term temps, hot and steamy through Monday then some
relief as that drier air starts to work in by Tuesday. At that time
we`ll see lows back down into the upper 60s with highs still near
90, but lower dewpoints.
&&
.LONG TERM...
(Wednesday through next Sunday)
Issued at 220 PM CDT Sun Aug 6 2023
In the extended forecast, not much pattern change as in general, a
west northwesterly ul regime resides. The flow will remain semi-
active but we can still hone in on Wednesday and Thursday as rather
wet. At that time, a more robust series of shortwaves will impact
our area. The NBE numbers have shown some copious rainfall amounts
with the last several runs. Looks like the builder will give us 2
inch amounts, or so, area wide. GFS is showing quite a bit more
across our east with the Euro close to 2 inches. In terms of severe
potential, SPC shows some activity upstream from us on Day 4, but
there is still no Day 5 eastward prorogation indicated at this time.
Further out, a secondary but weaker wave will bring another chance
of showers and tstms for Saturday.
For the extended temps, with the expected clouds and precip for Wed
and Thu, temps will run a few degrees below normal. Then, look for
conditions to normalize by the weekend with near 90 for highs
returning.
&&
.AVIATION...
(00Z TAFS)
Issued at 643 PM CDT Sun Aug 6 2023
A few storms may pop up overnight tonight, but terminals are
unlikely to be impacted. Expect southwesterly winds to increase
overnight ahead of an approaching front. Storms should start to
fire ahead of the frontal boundary by mid to late morning around
BNA and MQY, then intensify as they push east from late morning
through the afternoon. SRB and CSV may see gusty winds and
decreased visibilities as storms move across the Plateau.
Conditions should improve as storms continue to push east. Winds
will remain gusty through the end of the period.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 75 89 68 86 / 30 60 10 0
Clarksville 75 87 64 86 / 30 30 0 0
Crossville 68 82 61 78 / 30 90 10 0
Columbia 74 88 66 85 / 30 50 10 10
Cookeville 70 84 64 80 / 30 70 10 0
Jamestown 70 82 63 78 / 30 80 10 0
Lawrenceburg 73 87 66 83 / 30 60 10 10
Murfreesboro 73 89 66 86 / 20 60 10 10
Waverly 73 86 64 83 / 40 40 0 10
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......Mueller
SHORT TERM...21
LONG TERM....21
AVIATION.....Whitehead
Area Forecast Discussion
National Weather Service Mount Holly NJ
935 PM EDT Sun Aug 6 2023
.SYNOPSIS...
Weak high pressure moves away from the region tonight as low
pressure and an associated front approach. This low will move
across southern Ontario Monday and then across New England
Tuesday. After that, high pressure affects the area for the
middle of the week. Another disturbance will arrive Thursday but
probably have left the area before the end of the week.
&&
.NEAR TERM /THROUGH MONDAY NIGHT/...
9 PM update...No major changes were made to the forecast this
evening. Overall, trend was to up POPs to categorical for the
periods where we have confidence showers and thunderstorms are
goin to happen, mainly overnight tonight and again late
Monday/Monday evening. However, given uncertainty in between,
held POPS mostly at chance levels for the bulk of Monday across
a majority of the CWA, as there remains some guidance which
tries to keep spotty showers going thru the day. Given the
exceptionally moist air mass and slowly increasing forcing
aloft, this doesn`t seem impossible.
3 PM discussion...
High pressure over the area moves offshore tonight. Low
pressure over the Great Lakes and Ohio Valley will lift into
eastern Canada, and this will lift a warm front north through
the region late tonight through Monday morning. A strong storm
system then develops ahead of an approaching cold front Monday
afternoon and that system passes through Monday night as that
cold front works its way east.
Quiet conditions on tap for most of this evening as high
pressure centered over the Hudson Valley in New York state will
move offshore. Meanwhile, low pressure over the Ohio Valley will
lift to the north and east and move towards the Province of
Ontario in Canada. A warm front out ahead of that low will then
lift north through the region tonight. Shortwave energy will
pass through as well, and showers will develop with the passage
of the front.
Surface-based CAPE values will be minimal, and BUFKIT profiles
showing a developing inversion starting at around 925 mb. So
chances for convection will be minimal, and capped at slight
chance to chance. PWATs, however, will be upwards of 2 inches. A
30 to 40 kt LLJ will lift through as well. As a result, heavy
rain will develop, but unless there is significant training of
cells, not expecting a widespread flash flooding event. 1 hour
FFG values are 3 to 5 inches, and 3 hour FFG values are 3 to 5
inches, especially in the areas north and west of Philadelphia.
Any flash flooding will be localized, but there may be some more
widespread areas of urban and poor drainage flooding. The rain
tonight will, however, set the stage for Monday and Monday
night.
As rain tapers off from south to north, patchy fog will develop
in the early morning hours. It may take some time for the front
to fully lift to the north on Monday, so there are some
concerns about when the clouds will break up. By about midday or
so, skies should become partly to mostly sunny in Delmarva and
southern New Jersey, while breaks in the clouds will be harder
to get in the far northern zones. Highs on Monday will then
climb into the mid and upper 80s in Delmarva and along the urban
corridor from Trenton to Wilmington. Most elsewhere, highs will
be in the low to mid 80s, except for the southern Poconos and
northern New Jersey, where highs will be in the upper 70s to low
80s. Due to strong southerly flow, surface dew points will
climb into the low to mid 70s.
An upper trough will dig through the Great Lakes and Ohio
Valley, and shortwave energy out ahead of this trough will
approach in the afternoon and evening. Meanwhile, a surface cold
front ahead of this trough approaches as well.
There continues to be the potential for a fairly significant
severe weather outbreak over the area late Monday and Monday
evening that would produce not only severe winds, but flash
flooding as well. The Storm Prediction Center has Delmarva,
southeast Pennsylvania, and portions of southern New Jersey in
an Enhanced Rick for severe weather, with the rest of the
forecast area in a Slight Risk. The Weather Prediction Center
has the northern half of the forecast area in a Slight Risk for
excessive rainfall, with the rest of the area in a Marginal Risk
for excessive rainfall.
First, the severe weather. With the heat and humidity, surface-
based CAPE values will be upwards of 1500 to 2000 J/kg, but may
get higher in Delmarva if temperatures and dew points end up on
the higher side. 0-6 km Bulk Shear values will rise to 30 to 40
kt late Monday, and even 0-3 km Helicity values will be upwards
of 200 m^2/s^-2. A 40 to 45 kt LLJ will pass through the region
in the evening.
Although confidence is increasing in this outbreak occurring,
it should be noted that there are some timing and placement
concerns. The 12Z/06 NAM has one swath of convection going north
and west of the area, mainly in conjunction with the upper
trough, and another swath of convection passing south of
Delmarva, associated with strong shortwave energy. However, the
12Z/06 HRRR indicates what looks to be discrete supercells
forming a line by late afternoon/early evening, and passing
through the I-95 corridor from 6pm-9pm, with enhancement over
Delmarva. Will err on bringing convection into the far western
zones from 3pm-5pm, with the bulk of the activity occurring from
6pm-11pm. Damaging winds and large hail upwards of an inch or
so are expected during this time.
Now for the flooding. Although FFG values are high tonight,
between 1 and 2 inches of rain could fall, mainly north and west
of the I-95 corridor late tonight through Monday morning. With
high surface dew points, PWATs will be up to 2 to 2.5 inches.
With that strong LLJ passing through, heavy rain will develop
once again, and there will be better chance for flash flooding,
especially in the evening.
Storms should lose their intensity around midnight or so, and
will gradually taper off from west to east through the
overnight. Patchy fog will likely develop once again in the pre-
dawn hours. Lows Monday night will be in the upper 60s to low
70s.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
9 PM update...Guidance trend in this period seems to be
trending drier, so nudged POPS downward for Tuesday. No other
changes at this time.
3 PM discussion...
An upper trough and surface cold front will
move through on Tuesday with scattered showers and perhaps a few
thunderstorms developing in the late morning and afternoon. The
highest chance to see rain and thunderstorms looks to be north
and west of Philadelphia, though we are not expecting anything
like Monday in terms of severe at this time with model soundings
showing a lack of instability and shear. Temperatures will get
into the low to mid 80s with 70s in the Poconos, where clouds
and showers will keep things on the cooler side.
Cold front pushes through on Tuesday evening. As low pressure
slides by to the north, there will be around a 24 hour or so
period of a rather tight pressure gradient, which will keep
winds elevated through the night. Clouds will retreat northward
as the night goes on and most, if not everyone, will be clear by
dawn on Wednesday. Looks to be a spread of 60s across the CWA
for lows, with upper 50s in the higher elevations.
Wednesday looks to be rather nice as high pressure builds in.
It will still be a bit breezy through the day as the gradient
remains, with gusts around 20-25 MPH. It will feel quite
comfortable for a mid-August day, with dewpoints hovering around
60 or maybe even below. Highs will be in the low to mid 80s
with upper 70s in the higher elevations.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
The upper air pattern for the middle and later parts of the
upcoming week will continue to feature a ridge of high pressure
across the south and a subtle trough for the Great Lakes and
Northeast. This will keep conditions changeable and temperatures
mostly with a few degrees of normal into next weekend. The
warmest day, in our present forecast, could be Saturday when
some low 90s are possible for Delmarva and metro areas.
The fair weather across the area during Wednesday will continue
into the overnight as weak high pressure and an upper ridge
remain across the Middle Atlantic. Lows will be seasonable with
low 60s N/W and mid/upper 60s elsewhere.
Unsettled conditions will return Thursday but hopefully with
the quicker flow aloft, the system will (probably) only affect
that one day. The GFS/CMC 12Z models show a shortwave trough
will move through and low pressure and fronts will accompany it.
The latest EC model is slower with the system and keeps Thu dry
but brings rains for Friday. Beyond that, more typical summer
weather with seasonable temperatures and perhaps a few scattered
showers/tstms for the afternoon/evening hours.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Rest of Tonight (through 12Z)...VFR initially, then CIGs lower
to MVFR/IFR after 06Z. SHRA with VSBYs down to IFR will spread
over the terminals as well. Included VCTS in TAFs but may need
additional TEMPOS. S-SE winds 5 to 10 kt. Moderate confidence.
Monday (12Z through 00Z)...MVFR/IFR CIGs/VSBYs in stratus and
fog in the morning. VSBYs improve to VFR as fog burns off by
15Z, but CIGs may remains MVFR for a good part of the day.
Improvements to VFR not until 18Z or so. SHRA/TSRA will impact
KRDG/KABE after 21Z, and SHRA/TSRA may make it to
KTTN/KPNE/KPHL/KILG by 00Z. Damaging winds, large hail, and
heavy rain are all possible. S winds 5 to 10 kt, increasing to
10 to 15 kt with gusts up to 20 kt late. Moderate confidence
overall, low confidence on timing.
Monday night (00Z through 12Z)...SHRA/TSRA with sub-VFR
conditions, strong winds, hail, and heavy rain. Storms taper off
after 06Z, then CIG/VSBY restrictions in stratus and fog
possible. S winds 10 to 15 kt, becoming SW 5 to 10 kt. Moderate
confidence.
Outlook...
Tuesday...Primarily VFR, though sub-VFR conditions possible
with any showers. Best chance of showers look to be over
KRDG/KABE during the late morning/afternoon. Westerly winds
around 10-15 kt with gusts 20- 25 kt. Moderate confidence.
Tuesday Night...VFR. Westerly winds around 10 kt. Moderate
confidence.
Wednesday...VFR. West/Northwest winds around 10-15 kt with
gusts around 20 kt. High confidence.
Wed night... VFR expected.
Thu/Thu night... Scattered showers/tstms may bring lower
VSBYS/CIGS at times.
Fri... VFR expected.
&&
.MARINE...
Sub-Small Craft Advisory conditions tonight with S winds 10 to
15 kt and seas 2 to 4 feet. Showers, along with a few
thunderstorms, will result in lowered VSBYs, and then fog
develops late tonight through Monday morning.
On Monday, S winds increase to 15 to 20 kt with occasional
gusts up to 25 kt. Due to an inversion, not expecting 25+ kt
gusts to mix down, and seas should stay around 4 feet. Although
it may be close, will not hoist a SCA at this time. VSBYs should
improve during the day.
Monday night, strong to severe thunderstorms will affect the
waters with strong wind gusts, hail, and heavy rain. S winds 15
to 20 kt, becoming SW late. Seas around 4 feet.
Outlook...
Tuesday...SCA conditions possible. Southwesterly winds around
15-20 kt with gusts nearing 25 kt. Seas 3 to 5 feet.
Tuesday Night...SCA conditions likely on the coastal waters.
Westerly winds around 20 kt with gusts up to 30 kt. Seas 3 to 5
feet. Sub-SCA conditions are expected in the Delaware Bay as
gusts should remain below 25 kt there.
Wednesday...SCA conditions possible to start, though winds and
seas should relax in the afternoon to sub-SCA levels. Westerly
winds around 15-20 kt with gusts 25 kt to start and 3 to 5 foot
seas decreasing to 10-15 kt and 2 to 4 foot seas in the
afternoon.
Thursday...No marine headlines expected.
Friday...No marine headlines expected.
Rip currents...
On Monday, wind speeds increase, and the wind direction remains
onshore for the coastline of NJ and will be slightly onshore
for the Delaware beaches (at least for some of the day),
therefore a MODERATE risk for the development of dangerous rip
currents is currently forecast for the region.
By Tuesday, winds will shift to offshore, so should see
gradually improving conditions, but due to the elevated surf may
see one more day of MODERATE conditions at NJ, while DE is
currently forecast to be LOW.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.
&&
$$
SYNOPSIS...OHara
NEAR TERM...MPS/RCM
SHORT TERM...Hoeflich/RCM
LONG TERM...OHara
AVIATION...Hoeflich/MPS/OHara/RCM
MARINE...Hoeflich/Johnson/MPS/OHara
Area Forecast Discussion
National Weather Service Tucson AZ
245 PM MST Sun Aug 6 2023
.SYNOPSIS...Not as hot this upcoming week with a daily chance of
showers and thunderstorms.
&&
.DISCUSSION...The moisture push we had overnight has been nice but
still dealing with warm mid-level temperatures around -2 to -3 per
last POES satellite derived data. Latest HRRR and UofA WRF runs
still highlighting Santa Cruz and SW Cochise counties, mainly the
Santa Rita and Huachuca mountains this evening. Any outflows
pushing from these storms will struggle to develop additional
storms with most of the isolated activity that does develop this
evening staying south of a Kitt Peak to Benson line.
With the upper high sliding a little further east, it will not be
as hot this upcoming week with highs running a few degrees above
normal. Relatively active convective week ahead with daily 10% to
40% chances then drying out next weekend and unfortunately
heating back up.
&&
.AVIATION...Valid through 08/00Z.
Chance of -SHRA/-TSRA with clouds bases 8k-10k ft AGL until
07/04z across Santa Cruz and SW Cochise county impacting KOLS and
KALK. Otherwise SKC conds. Chance of afternoon -SHRA/-TSRA across
most of the area Monday. SFC winds NWLY at 10-15 kts with gusts
up to 25 kts possible until 07/03Z. Otherwise SFC winds will be
variable and remain under 10 kts. Aviation discussion not updated
for TAF amendments.
&&
.FIRE WEATHER...There was a moisture increase this morning which
will remain across the area much of the upcoming week. This will
lead to daily chances of showers and thunderstorms, although not
everybody will be getting wetting rains. Temperatures will not be
as hot this week, generally a few degrees above normal. Drying
out once again next weekend with temperatures heating back up
again.
&&
.CLIMATE...The low temperature at the Tucson airport this morning
was a very warm 85 degrees. This ties for the warmest August low
on record, which first occurred on August 1, 1902 and was later
tied on August 1, 1914.
The consecutive day streak of highs 100 degrees or hotter in
Tucson stands at 52 days. The probabilities each day this
upcoming week of NOT hitting 100 degrees is less than 10%.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM MST this evening for AZZ501>509.
&&
$$
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Area Forecast Discussion
National Weather Service Las Vegas NV
1222 PM PDT Sun Aug 6 2023
.SYNOPSIS...High pressure maintains warm and dry conditions over the
next few days. Gusty southwesterly winds develop as a series of
disturbances move in from the west coast. A boost in moisture from
the remnants of Tropical Storm Eugene will bring increased shower
and thunderstorm activity starting Wednesday, lasting through the
weekend.
&&
.SHORT TERM...Through Tuesday Evening.
A high pressure system is in place over the southern international
border. At the same time, a shortwave trough is moving east towards
the California coast. These two features create southwesterly flow
over the forecast area, and breezy afternoon winds are expected to
pick up through Tuesday as a series of disturbances move along the
flow pattern. High temperatures today and tomorrow will be a degree
or two above normal for this time of year, falling to slightly below
normal on Tuesday as the ridge is pushed east. Isolated thunderstorm
potential returns on Tuesday afternoon and evening as increased
moisture reaches southeastern Mohave County. Most convection should
be limited to higher terrain. Lastly, the HRRR indicates that smoke
from the No Name Fire near the Kern/Inyo county line in California
will be carried with the southwesterly winds towards areas of
eastern California and southern Nevada.
.LONG TERM...Wednesday through Saturday.
A gradual increase in mid-level moisture will arrive Wednesday
and beyond as a decaying tropical disturbance slowly drifts north
off the Baja coast. Precipitable water values will climb most
dramatically Thursday and Friday, though most of the increase will
come from a moistening of the mid-levels as opposed to the
surface. Nonetheless, enough moisture and instability may be
present for a small uptick in shower and thunderstorm coverage
late in the week. In fact, the ECMWF ensembles which previously
has been drier than GFS have Begin to advertise some light QPF
across our western zones associated with what little remains of
the tropical disturbance by late in the week.
Details are likely to change, but an increase in cloud cover will
keep our temperatures near seasonal normals and some slight chances
for showers and thunderstorms are possible, especially in the higher
terrain, by late in the week.
&&
.AVIATION...For Harry Reid...South to southwest winds of 10-14kts
with gusts to 20kts are expected through this afternoon and early
evening. The gustiness will end after sunset, but winds will remain
out of the southwest, generally less than 9kts, through the
overnight period. Similar winds are expected tomorrow, with winds
increasing to 12-18kts with gusts to 25kts during the afternoon.
Skies will remain mostly clear throughout the forecast period.
For the rest of southern Nevada, northwest Arizona and southeast
California...Winds following typical diurnal patterns are expected
areawide through the TAF period. The highest wind gusts will
continue to be across the western Mojave Desert, where gusts to
around 25kts are likely later this afternoon and evening. Otherwise,
wind speeds of 8 to 20 kts can be expected into Monday. Skies will
remain mostly clear throughout the forecast period across the
region.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
SHORT TERM...Meltzer
LONG TERM...Outler
AVIATION...Planz
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