Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/11/23
Area Forecast Discussion
National Weather Service La Crosse WI
1030 PM CDT Thu Aug 10 2023
.UPDATED...
Issued at 911 PM CDT Thu Aug 10 2023
Convection is erupting across the SD/southwest MN border at mid
evening, due to an upper level shortwave trough and 35 kt low level
jet/moisture transport. Storms are feeding off a MLCAPE pool of
2000+ J/kg with effective shear 30-40 kts. Hail and wind threats.
These storms will continue to march east overnight while a northwest-
southeast lying warm front inching northward into central
MN/southwest WI. Instability will be weakening locally, but still
around 1000 J/kg of MLCAPE per SPC RAP analysis to work on. 30 ish
kts of effective bulk shear could still be in play. CAMS suggest
that the storms could cluster into an mcs with the heart of the
system dropping southeast into IA. Its the southern portion of the
system that could pack a stronger punch, with less favorable
atmosphere farther north. Overall, storms look to move into SE MN/NE
IA toward 06-07z and a few could still be strong with stronger wind
gusts and locally heavy downpours. CAMS are at odds with how the
northern portion of the convection plays out...some hold it together
while others weaken to scattered showers. For now, focus for
stronger storm concerns lie west of the Mississippi River. Can`t
necessarily rule out isolated severe, but much will depend on how
the system develops over the next few hours.
.DISCUSSION...(This evening through Thursday)
Issued at 930 PM CDT Thu Aug 10 2023
Key Messages:
- Decaying band of showers and storms moves through tonight into
early tomorrow morning with minimal impacts expected.
- Thunderstorms redevelop Friday afternoon over eastern Minnesota
and race eastward across the region (40-60% chance). Several of
these storms may become severe with large hail up to 2 inches
in diameter and damaging winds of 60-70 mph will be the main
threats.
- Pleasant weather for Saturday, with periodic risks for storms
next week.
This Afternoon and Tonight:
Early afternoon water vapor imagery shows the region already
undergoing a pattern shift as upper tropospheric ridging slides
to the east and a sharp shortwave digs over the western Dakotas.
High-based showers have persisted through the morning along a
295-305 K isentropic upglide corridor/warm front over central
Minnesota. These showers should migrate southeastward and linger
through the evening as the frontal surface as a whole lifts
northeastward. The main convective show ignites over the eastern
Dakotas along the cold front and races eastward this evening,
reaching southeast Minnesota close to the midnight timeframe. The
overall complex will be on a weakening trend through Friday
morning as it outruns the MUCAPE corridor; however, explicit CAM
reflectivity progs do show most locales seeing some rainfall from
this system.
Friday/Friday Night:
The overall trend over the last 24 hours has been for Friday
morning`s convective complex to depart earlier than previously
forecast, allowing for more of an airmass recovery ahead of the cold
front. The 12Z HREF SBCAPE mean values increase to around 1500 J/kg
with deep westerly shear increasing to 30-50 kts as a 90-kt jet
wraps around the base of the advancing shortwave. Convective
initiation is expected along or slightly ahead of the cold front
in eastern Minnesota by 21-23Z. Straight, elongated hodographs
will promote both a fast forward motion of 30-35 kts and discrete
supercellular structures as the storms quickly work off the
initiating boundary. Splitting storms are likely given the lack of
any concavity in the hodographs, which should eventually lead to
upscale growth over the course of the evening.
The main threats with this event look to be focused on large hail
and damaging winds. The favorable hodograph structures, coupled with
any rotating updrafts, should promote hail of 1-2 inches in diameter
with the remote possibility that 2+ hail could occur with an
exceptionally strong mesocyclone/updraft. The fast forward
motions and the potential for evaporative cooling of the airmass
below hail cores will promote a damaging wind threat with any of
these cells as well. While the tornado threat is non-zero, it
would take a modest augmentation of the low-level wind field (or
storm mode) to realize any such threat.
The storms should progress quickly through the forecast area and
depart by 10 pm.
Saturday/Sunday:
Ridging amplifies over the Northern Plains for Saturday, resulting
in dry and pleasant conditions. Drier air filtering southeastward
behind Friday`s front results in deeper mixing in the afternoon
hours. Winds at the top of the boundary layer may push 25-30 kts,
thus gusts of 20-25 kts are likely in the afternoon. By Sunday,
the progressive pattern ushers the ridge eastward and another
sharp shortwave digs over the Dakotas and Minnesota during the
day. Given the rapid arrival of the wave, the model guidance vary
on the northern extent of the surface warm front, with solutions
ranging from southern Iowa to southern Minnesota. The placement of
this boundary will be key for where the corridor of severe
weather sets up on Sunday afternoon. This the next system to
watch, especially if the models start to trend north with the warm
front.
Monday - Thursday:
Cold air advection, clouds, and scattered showers start the new work
week and should keep high temperatures in the 70s. The upper trough
departs during the day and ridging builds in for the day on Tuesday.
The wave train keeps chugging ahead with another shortwave
Tuesday night that could bring scattered showers and storms. The
subtle and progressive nature of upper tropospheric pattern
results in slow but steady degradation in forecast confidence
moving into midweek, but the pattern of storm chances roughly every
other day seems to hold true for the remainder of the forecast
period.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1030 PM CDT Thu Aug 10 2023
CIGS: lower deck associated with shra/shortwave trough pushing in
from the east overnight. Short term guidance supports a drop into
MVFR for a few hours early Fri morning (10-15z ish) before
scattering out.
WX/VSBY: band of showers/storms expected to shift west-east across
the area overnight, tied to an upper level shortwave. CAMS models
favor 07-11z as the most likely period (some MVFR vsby impacts
possible). Some of the latest short term guidance dives the bulk of
the convection southeast into IA, with only a short period of -shra
at KLSE. Will add mention of thunder at KRST for T at KRST for
now.
Scattered storms then looking likely for the late afternoon/early
evening hours. Fast moving, strong-severe storms which would kick
off over south-central MN by 19-20z, tracking east. Will continue
VCTS to cover potential impacts but add a short tempo group for
most likely period for storms.
WINDS: southeasterly goes south and then westward Fri morning. Some
uptick for the afternoon hours with a few gusts around 20 mph
possible.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
UPDATED....Rieck
DISCUSSION...Skow
AVIATION.....Rieck
Area Forecast Discussion
National Weather Service Binghamton NY
945 PM EDT Thu Aug 10 2023
.SYNOPSIS...
Quiet weather is expected through Friday before the pattern
becomes somewhat more active with more rain beginning Saturday.
&&
.NEAR TERM /THROUGH FRIDAY NIGHT/...
930 pm update...
As mentioned earlier, we`ve reintroduced valley fog into the
forecast and may have to go with the dense terminology since
observations in the area are already suggesting early development.
This could just be an immediate post rain reaction that we`ve
seen before which may actually abate some during the overnight
as cooler and drier air works in behind the surface front.
Overnight lows will still be meeting and exceeding crossover
temperature, so I`m going to favor the fog continuing to develop
through the night. Regarding the other challenge of potential
lake effect precipitation...I`m still not seeing the thermal
data to support showers in the Western Mohawk Valley tonight.
Cloud plumes...yes. On the other hand, the reliable GEM model is
suggesting some light QPF. Have trended the PoPs down a bit to
shrink some of the previous coverage...otherwise since the PoPs
are so low anyway, it`s not really enough to kick it all out,
either. We`ll call it a chance of sprinkles.
No changes to temps and dewpoints as they are generally trending
well.
630 pm update...
Scattered showers continue to sweep to the ESE through CNY and
NEPA while gradually weakening as they move into more stable air
that had been covered in clouds all day. The HRRR short range
CAM guidance appears to be best at handling these trends and
suggests that the whole region will be rain free by 9 PM.
Satellite also shows skies becoming partly cloudy...and then
mainly clear for the overnight. A couple minor issues to
consider are weak lake effect showers previously included in the
forecast for the Western Mohawk Valley overnight, as well as
valley fog formation. Will introduce patchy fog, mainly for the
Twin Tiers and Delaware Valley. I haven`t seen any solid
evidence to make changes to the slight chance of a lake Ontario
response, but did allow for a larger precipitation free time
gap between the current activity and any new development.
330 pm update...
Scattered showers continue across the area. Clouds have kept the
instability low. Some breaks in the clouds moving into the
Finger Lakes is creating better instability. This is ahead of
one broken weak line of showers first and further upstream a
broken line of showers and weakening thunderstorms moving off of
Lake Ontario. These no severe thunderstorms should further
weaken as they move southeast into our area through 8 PM.
Showers will end across the area by 10 pm. Rainfall rates and
rain totals should stay low enough so that flash flooding will
be zip in most locations. Best chance across the Finger Lakes
into Oneida County where rainfall amounts have been higher and
thunderstorms may make it into the area with brief periods of
heavy rain.
Around midnight behind the front cold air will start the lake
effect machine ESE of Lake Ontario into CNY but especially
Onondaga, Madison, and Oneida Counties. Showers are likely but
amounts will be light. Further south skies will start to clear
which could allow valley fog to form from south central NY into
NEPA. Low temperatures will be in the mid and upper 50s.
A strengthening ridge of high pressure at the surface and aloft
will move in Friday with mostly sunny skies. It will be dry
with gusty winds. It will be cooler than average with highs from
the mid 70s to around 80.
Friday night will continue to be dry. Clouds will move in late
at night ahead of the next system. Showers will hold off until
after sunrise Saturday. There is a chance of valley fog again
under the ridge. Temperatures will fall quickly with clear skies
and calm winds in the evening. Lows will be in the 50s.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
215 PM Update...
Next shortwave and associated surface cold front will push
through the region on Saturday. Still some uncertainty exists on
the overall timing with the front, but models are starting to
hone in on early Saturday afternoon through Saturday evening.
High pressure will slide east early Saturday and SW return will
develop ahead of the incoming front. However, overall, moisture
and instability does not look too impressive at this time, but
some guidance is showing CAPE values of 1000 J/kg or just over.
There will be plenty of shear available, with NAM showing 35 to
40 knots of 0-6 km bulk shear. There will likely be some
potential for severe thunderstorms to develop Saturday
afternoon, especially if the front slows down some and more
instability can be realized Saturday afternoon. For now, SPC has
the area highlighted in a marginal risk, which is to be expected
due to the current uncertainty with instability. Will have to
continue to monitor with the next few model runs and if the
front does slow down some, then the severe threat will increase
some. After the front crosses Saturday night, the upper trough
will remain overhead and some leftover showers may linger into
Sunday before high pressure starts to build into the area
through the day Sunday.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
225 PM Update...
Still quite a bit of spread in the models for the system towards
the beginning of next week. Due to this uncertainty, NBM spreads
out PoP for too long than what will actually happen, but
thinking the best chance for showers and thunderstorms will be
late Monday into Tuesday. The upper trough could linger in the
region until mid week, so Tuesday could also be unsettled with
diurnal showers and thunderstorms focused around peak heating
during the afternoon. There will likely be periods of dry
conditions through mid week onwards, however a trough pattern
will hold in place and slight to low chances for showers and
weak storms will be possible through the remainder of the
period.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Showers have dissipated across the area, leaving VFR conditions
through the evening hours. High pressure and clearing skies
build in from the west, bringing NW flow across the area
tonight. This will allow for valley fog to form and lake
enhanced low level cloud deck across the northern portion of the
area.
ELM will be the most impacted, with conditions dropping to LIFR
after 8z and into the morning hours due to fog. Conditions
should quickly improve after 13z as winds pick up, bringing VFR
conditions through the day.
RME is expected to see IFR ceilings and patchy fog thanks to
lake enhanced clouds moving over the area tonight. Conditions
are not expected to improve to VFR until late morning when the
winds pick up and the clouds mix out.
BGM and AVP will be tricky tonight as guidance is hinting at
some IFR conditions but the wind profile looks to be a little
too strong to allow for fog to settle in. Confidence is high
enough to include a tempo for IFR "sunrise surprise" that tends
to happen when valley fog lifts up the hills and impacts the
airports around sunrise, especially at BGM. Hopefully, guidance
will be a little more clear with the next TAF package.
SYR looks to be VFR through the period. MVFR ceilings could
move overhead later tonight if the winds shift a little to the
WNW but confidence in this happening was too low to include in
the TAF.
Outlook...
Friday night...Mainly VFR.
Saturday through Sunday...Restrictions likely in showers and
thunderstorms.
Monday...mainly VFR.
Monday night through Tuesday...restrictions likely in showers
and thunderstorms.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.
&&
$$
SYNOPSIS...JAB/TAC
NEAR TERM...JAB/TAC
SHORT TERM...MPK
LONG TERM...KL/MPK
AVIATION...JTC
Area Forecast Discussion
National Weather Service Boston/Norton MA
1007 PM EDT Thu Aug 10 2023
.SYNOPSIS...
Another weather system will be moving into the area through the
early overnight hours, bringing the potential for heavy
downpours and possible a strong thunderstorm across south
coastal areas. Drier and more seasonable for Friday into early
Saturday. It should be a very active weather pattern this
weekend into next week. Scattered, but strong, thunderstorms are
possible both Saturday and Sunday. After a brief break Monday,
more showers and thunderstorms, with heavy rainfall, are
expected Monday night and Tuesday.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
10 PM update...
Bulk of convection has remained to the south deeper into the
warm sector. Some heavier showers lifting across northern MA,
with a second area of showers and embedded t-storms skirting the
south coast. Colder cloud tops across eastern New Eng and will
be moving offshore overnight leading to drying conditions as
cold front sweeps through followed by W/NW flow and dropping
PWATs. Showers and a few t-storms may linger on the Cape into
the early morning, otherwise expect clearing skies late
tonight. Adjusted PoPs for current radar trends. Lower
dewpoints will be moving in from the west overnight, dropping
into the 50s in western MA and low/mid 60s in SE MA toward
daybreak.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
145 pm update...
12z guidance has not differed much from previous runs. Looks
like a great day for those who enjoy dry, summer weather. Decent
boundary layer mixing should be able to tap into the 20-25kt
winds a few thousand feet above the surface, so a little breezy
in the afternoon. High temperatures won`t be too far from
normal, with lots of lower 80s (70s in the higher terrain).
Dewpoints will be dropping into the 50s, providing that
comfortable feeling. Enjoy it if you can.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Highlights
* Potential for strong/severe thunderstorms Saturday night,
especially across the western half of southern New England.
* Potential for strong/severe thunderstorms and heavy rain
Sunday, especially south of the Mass Pike.
* Warm front may bring torrential rain and isolated severe
weather late Monday night and Tuesday.
Have moderate confidence in the overall forecast into this
weekend. After then, timing differences of smaller features
start to dominate the solutions near our neck of the woods,
resulting in lower confidence into next week.
Friday night through early Saturday afternoon...
This is still looking like a quiet period, with mainly clear
skies and high pressure in control of the weather. There could
be local sea breezes early Saturday afternoon. Below normal
temperatures Friday night, trending to near to slightly above
normal Saturday.
Late Saturday afternoon through Sunday...
A mid level open wave is still expected to move across southeast
Canada this weekend. This will also keep a surface low pressure
to our north as well. Some question as to how many strong to
severe thunderstorms there may be during this time. The NAM is
more aggressive with this potential than most of the other
guidance sources. This will need to be adjusted with later
forecasts. At this time, am more concerned about Saturday
afternoon and evening than Sunday.
Near to slightly above normal temperatures anticipated.
Sunday night through early Monday afternoon...
A cold front moving offshore by Sunday evening should be
followed by a weak high pressure into Monday. Near normal
temperatures anticipated.
Later Monday afternoon through Tuesday...
This continues to look like a period of wet weather for southern
New England. Similar situation to this weekend, with another
surface low pressure tracking across southeast Canada. Given the
uncertainty at this time range, will continue to monitor both
the severe and flooding potential.
Wednesday through Thursday...
High pressure is expected to be somewhere between the central
Appalachians and the Mid Atlantic coast. Dry and seasonable
weather is expected, with a pair of fronts kept to our NW and
SE.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Moderate confidence through 09z. High confidence after that.
VFR for most right now. Losing confidence in many thunderstorms
across southern New England overnight. As such, removed the
mention from most terminals. Kept a mention at ACK, though even
there, the threat is lower.
The other concern tonight will be the occurrence of IFR. Latest
LAMP and RAP still indicated many areas getting into at least
MVFR for a time tonight. Thinking IFR will be isolated and brief
tonight. Favored not going lower than MVFR for most. Even then,
expecting all areas to be VFR by the Friday morning push.
VFR then continues through Friday. Should see W/NW surface
winds gust 20-25kt during the afternoon.
KBOS TAF...Moderate confidence through 06z. High after that. No
mention of TS at this time, since probabilities are generally
less than 30%.
KBDL TAF...Moderate confidence through 04z. High Confidence
after that.
Outlook /Friday Night through Tuesday/...
Friday Night: VFR.
Saturday: VFR. Slight chance SHRA.
Saturday Night: VFR. Chance SHRA, isolated TSRA.
Sunday: VFR. Breezy. Chance SHRA.
Sunday Night through Monday: VFR.
Monday Night: Mainly VFR, with local MVFR possible. Breezy.
Chance SHRA, isolated TSRA.
Tuesday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
315 pm update...
High confidence
Showers and a few thunderstorms will move across the coastal
waters this evening through the early overnight hours. This is
out ahead of a front which will move off the east coast during
the pre-dawn hours. A few of the thunderstorms south of the Cape
and around the Islands and the outer southern marine zones could
become strong this evening. A waterspout is not out of the
question. Friday will feature plenty of sunshine, and
west/northwest winds up to 20kt. Seas across the outer marine
zones may approach 5ft, but will not raise any small craft
advisory at this time since that is so marginal.
Outlook /Friday Night through Tuesday/...
Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Saturday: Winds less than 25 kt.
Saturday Night through Sunday: Winds less than 25 kt. Slight
chance of rain showers.
Sunday Night through Monday: Winds less than 25 kt.
Monday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas locally approaching 5 ft. Chance of
rain showers.
Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Belk/Nash
NEAR TERM...KJC
SHORT TERM...Nash
LONG TERM...Belk
AVIATION...Belk/Nash
MARINE...Belk/Nash
Area Forecast Discussion
National Weather Service Columbia SC
815 PM EDT Thu Aug 10 2023
.SYNOPSIS...
A weak cold front in North Carolina this evening will move
south and become nearly stationary across the area late tonight.
As an upper level trough approaches Friday, deep moisture will
spread into the area. Scattered to numerous showers and
thunderstorms are expected to focus near the front. Diurnally
driven convection returns over the weekend with typical
summertime heat. Another cold front impacts the region early
next week.
&&
.NEAR TERM /UNTIL 7 AM FRIDAY MORNING/...
A weak cold front in North Carolina this evening will move
southeast into central South Carolina late tonight. Radar was
showing a few isolated showers north of the area, but they have
dissipated as the weak short wave moved into eastern North
Carolina. Strong mixing this afternoon has lead to drier air
across the area. Satellite suggesting mainly high thin clouds
most of the night with diminishing winds. Expect some lower
clouds toward daybreak. Cut overnight lows just a tad. So, upper
60s north to low 70s south. The latest HRRR is slower developing
showers toward morning near the AGS area so cut pops a bit
especially before 10z.
&&
.SHORT TERM /7 AM FRIDAY MORNING THROUGH SUNDAY/...
A frontal boundary stalls over The Midlands and CSRA on Friday.
Convective allowing models show showers and thunderstorms developing
along this boundary in response to a short wave upper trough
moving through the Carolinas. Gusty winds and brief heavy
rainfall will be the primary concerns near stronger
thunderstorms. It will be rather muggy with PW values in excess
of two inches.
High pressure aloft builds eastward this weekend which will lead to
much warmer high temperatures. Expect highs in the mid to upper 90s
along with dew points in the lower to mid 70s. This will raise
apparent temperatures into the 102-107 degree range on Saturday and
110-115 range on Sunday. A Heat Advisory looks likely on Sunday.
Isolated diurnal convection will be possible mainly across higher
terrain and near the sea breeze front.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Monday looks like another hot and humid day ahead of an strong upper
level trough moving into the Ohio River Valley. There is a chance of
showers and thunderstorms Monday afternoon and evening as the
front moves through the region.
A slightly cooler and somewhat drier airmass moves into the region
in a northwest flow aloft behind the upper trough. The Southeast
U.S. will be under a flat H5 ridge axis during the middle of next
week with an unusually active jet stream for mid August across the
Great Lakes and Northeast U.S. Expect near normal temperatures and
below normal chances of precipitation.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
VFR Conditions expected through the TAF period.
Winds are decreasing at the terminals this evening, expected to
become generally light and variable tonight. While guidance is
hinting at the potential for fog to develop northeast of the
terminals, generally low potential at the terminals as little to
no precip was observed today and crossover temperatures are in
the low to mid 60s, creating an unfavorable fog environment.
Cannot completely rule out fog at AGS but it would be brief and
shallow. A line of showers and storms develops tonight well to
the west and will move towards the terminals but uncertainty as
to whether showers or storms maintain themselves as they
approach the area Friday morning.
EXTENDED AVIATION OUTLOOK...Moisture increases into the
weekend, increasing the chances for early morning fog/stratus.
Restrictions also possible in mainly diurnal convection through
the extended.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Dodge City KS
1031 PM CDT Thu Aug 10 2023
...Updated Aviation...
.SHORT TERM...(This evening through Friday night)
Issued at 1240 PM CDT Thu Aug 10 2023
Water vapor satellite imagery and RAP upper air analysis midday
Thursday indicates west-northwesterly flow remains fixed over the
central plains between a broad subtropical ridge over the
southern plains/northern Mexico and a pair of shortwave troughs
over southern Ontario and Saskatchewan, Canada. This pattern is
providing sufficient momentum over the Rockies to sustain weak
surface lee troughing spread out across the northern and central
plains. Downsloping south-southwesterly low-level flow around this
surface trough will result in increasing temperatures today, with
afternoon highs climbing into the low/mid 90s. Latest CAMs/HREF
suggest a few stray thunderstorms developing in eastern
CO/northwest KS will wander into our north/northwest zones. Given
the lack of appreciable synoptic support, convective coverage
will be low, so most locations will remain dry. However, inherited
slight chance pops (15-24%) were maintained to cover this
scenario. For the majority of southwest KS, Thursday night will be
quiet, with lows dropping into the mid 60s to low 70s.
Roughly zonal 500-mb flow will continue over the central plains
daytime Friday, as the aforementioned pair of shortwave troughs in
southern Canada shift east-southeast. The surface lee trough will
slide east ahead of the western shortwave trough, sending a weak
cold front into southwest KS during the morning and early
afternoon. Unfortunately, this boundary will fail to inhibit the
warming trend, and afternoon highs will tick up a few degrees into
the mid/upper 90s. What this front will do is help spark scattered
thunderstorms that CAMs/HREF suggest will favor the southeast
zones, so another day of slight chance (15-24%) to low-end chance
(25-54%) pops is on tap for those areas. Thunderstorm activity
will exit stage right during the 06-09Z Saturday time period, and
southwest KS will see lows dropping into the mid 60s/low 70s once
again.
.LONG TERM...(Saturday through Thursday)
Issued at 222 PM CDT Thu Aug 10 2023
Latest medium range ensembles agree active weather will return to
southwest KS over the weekend, as both the GEFS and EPS show a
weak, closed low associated with the seasonal monsoon reaching
the southern CA coast by 12Z Saturday. Weak shortwave
perturbations on this feature`s eastern periphery ejecting
northeastward through the Four Corners region will support
convective development Saturday afternoon/evening in eastern CO
that will spread east into our area with time, likely in the form
of a loosely organized MCS. Some severe potential will exist with
this activity, however generally weak flow throughout the low to
mid troposphere will limit hodograph size/curvature, restricting
severe coverage.
Another round of widespread precipitation is expected Sunday
afternoon/evening into the overnight period as a strong upper
level shortwave trough digs southeast into the northern
plains/upper Midwest and sends a strong cold front (by August
standards) southward through our area. Confidence is high in
thunderstorms along this boundary given all members of the EPS and
80% of the GEFS members show significant QPF, and this is
reflected by NBM pops well into the likely category (55-74%). A
slight uptick in 500-mb flow associated with the digging trough
will somewhat enhance deep-layer shear, suggesting a higher
degree of storm organization is possible with this round of
convection. Primary severe hazard will likely be damaging wind
gusts as the expected storm mode will be linear along the surging
front.
Strong north winds early Monday behind the front will gradually
weaken throughout the day as surface high pressure builds into the
central plains. Resulting CAA from these winds will foster another
afternoon of well below normal temperatures for southwest KS, as
highs only reach the low/mid 80s. Unfortunately, this cool air
will not last more than a day, as GEFS/EPS ensemble means show the
subtropical ridge rebuilding northwestward Tuesday into the
western CONUS, and being maintained through the end of the long
term period. Synoptic-scale subsidence, warming 850-mb
temperatures, and plenty of solar insolation all will contribute
to afternoon highs increasing back into the 90s Tuesday through
Thursday.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1031 PM CDT Thu Aug 10 2023
Excellent flying weather will continue through this TAF cycle,
with VFR/SKC, scattered mid/high clouds at times, and light winds
(generally 10 kts or less, variable in direction). An isolated
thunderstorm is possible around 00z Sat, but again confidence in
coverage and impacts on terminals is far too low for inclusion in
this set of TAFs.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 69 96 68 94 / 10 20 20 10
GCK 67 94 66 90 / 20 10 10 10
EHA 65 95 66 90 / 20 10 10 30
LBL 68 95 68 92 / 20 10 10 20
HYS 67 97 66 93 / 20 10 10 10
P28 70 95 72 95 / 10 20 30 20
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Springer
LONG TERM...Springer
AVIATION...Turner
Area Forecast Discussion
National Weather Service Des Moines IA
637 PM CDT Thu Aug 10 2023
...Updated for the 00z Aviation Discussion...
.DISCUSSION.../Tonight through Thursday/
Issued at 329 PM CDT Thu Aug 10 2023
Key Messages:
- Storms tonight, some may produce strong wind gusts.
- Additional storm chances Friday evening, then more widespread
storms possible Sunday into Sunday night.
Active northwesterly synoptic flow will continue to dominate the
forecast through the week ahead. Our next opportunity for precip is
quickly approaching as GOES water vapor imagery shows a shortwave
trough pushing into the Dakotas. A complex of storms is progged to
develop over the eastern Dakotas late this afternoon and evening and
accelerate south and east into tonight. Most CAMs suggest storms
reaching our western counties around or shortly after 10pm. Sounding
profiles shows a bit more dry air is present compared to more recent
convective episodes, which models are latching on to and producing
sporadic strong wind gusts as storms begin to decay and become
increasingly elevated with eastward extent overnight. Hi-res
guidance has had some difficulty with storm evolution and coverage,
especially the HRRR which had backed off considerably with previous
runs but has since come back around to more widespread activity
overnight.
Storms push off to the east early tomorrow morning and give way
to a lull for a sizable chunk of the day as highs warm to near 90.
Models fire another round of convection along a secondary upper
wave and attendant frontal boundary by late afternoon/evening.
Weak convergence along the boundary and poor upper support may
limit spatial coverage to just isolated or scattered. However, any
storms that fire will be working within a favorable parameter
space for intense, organized updrafts capable of large hail and
damaging winds, particularly over the eastern tiers of the cwa.
An area of surface high pressure sags south through the region on
Saturday, leading to pleasant and dry conditions with highs in the
70s to near 80. Atmosphere quickly becomes unsettled once again as
an upper wave matures as it drops south from central Canada and into
the Great Lakes. Showers/storms are likely Sunday into Sunday night
as kinematic and thermal forcing mechanisms phase within a moist
environment. Unseasonably fast mid-level flow will promote high deep
layer shear values for this time of year, however instability in the
boundary layer remains uncertain due to the potential for early day
precipitation. Severe weather potential will need to be closely
monitored.
Quiet conditions return early next week as deep layer subsidence and
breezy, dry northwest winds push through the state. Expecting
periodic chances for precip to return toward the latter half of next
week as the active northwest flow pushes more shortwaves through the
region.
&&
.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 631 PM CDT Thu Aug 10 2023
Initially, VFR conditions will prevail across the sites. This
evening and overnight, thunderstorms remain expected to develop
and overspread the area from W/NW. SHRA/VCTS mentions are at all
sites, with only limited restrictions mentions with regards to
visibility and ceilings. Expect periods of strong winds and
reduced visibilities within thunderstorms that overpass TAF
sites. Restrictive cloud decks will be possible as well.
Conditions quickly return to VFR in the early morning to mid
morning hours across all sites.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Martin
AVIATION...Curtis
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1153 PM EDT Thu Aug 10 2023
.AVIATION...
Large scale support tonight turns towards sharp 1000-500mb
geopotential height rises and increasing anticyclonic flow
trajectories. Survey of forecast soundings depict active and lowering
subsidence mainly between 3.0 - 7.0 kft agl. VFR conditions tonight.
May observe some shallow ground fog or haze around daybreak for the
taf sites away from the urban heat island. Quiet weather for a good
chunk of the early day period Friday. Attention then turns towards
increasing thetae in advance of a weak area of low pressure. Two
distinct features of interest are a retreating surface warm
front/deformation axis between 22-01Z Friday evening, then a
meridional deeper moisture transport axis pushing across the taf
sites between Friday night between 03-06Z. Have introduced timing the
shower and thunderstorm potential with Prob30 groups.
.DTW THRESHOLD PROBABILITIES...
* Low for thunderstorms between 22Z Friday and 01Z Saturday. Also
low for thunderstorms between 03Z Saturday and 06Z Saturday.
&&
.PREV DISCUSSION...
Issued at 353 PM EDT Thu Aug 10 2023
DISCUSSION...
Scattered showers and a few thunderstorms persist across the cwa per
KDTX radar. Storms along/south of I-94 have exhibited the strongest
reflectivity cores, but will move out of the cwa within the next
hour or so. These storms will be capable of gusts in excess of 40
mph. Subsidence aloft limits additional convective development
through the evening, so will see a gradual decrease in PoPs as the
ongoing cells propagate east. Post-frontal subsidence continues to
gain traction through the evening and overnight, producing favorable
radiational cooling conditions which combined with northwest
flow/dry Canadian air allows lows to dip into the mid 50s.
This drier airmass will be short-lived as elevated portions of the
warm front begin to lift into lower Michigan throughout Friday
morning. Resident static stability/isentropic downglide from today`s
system look to hold on until after 16z (12pm local time), which will
tend to limit earlier elevated convective activity in spite of
strong elevated forcing along the theta-e gradient. Still, cannot
rule a few showers early in the day.
Will have to watch the evolution of an upstream MCS (projected to be
over central Wisconsin/Illinois by 12z Friday), which hi-res
guidance suggests may eat into upstream instability over Illinois
and Indiana. Still, with the warm front likely already on our
doorstep by that point, anticipating at least pockets of marginal
instability (1000-1500 J/kg) building into southeast Michigan by
early afternoon. Bulk shear parameter space is similarly marginal,
with 12z.HREF ensemble mean around 30 knots. For southeast Michigan
standards, this is likely enough to produce at least isolated strong
to severe storms, primarily south and west of the warm front which
stalls over the northern part of the cwa. Attm cannot rule out any
hazards, given both discrete and linear storm modes as well as
boundary interactions that could locally augment shear profiles and
produce rotating storms, but will again note the marginal broad
parameter space that keeps these types of storms isolated. A few
things to keep an eye on will be low pressure organizing quickly
over northern lower Michigan as convection is ongoing, which could
support some slight backing of the winds, noted in the 06z Euro/15z
RAP with the nose of a LLJ inching toward southeast Michigan late in
the day.
Eventual transition to elevated storms occurs with loss of daytime
heating Friday night, coinciding with the arrival of more energetic
upper level dynamics. Above the boundary layer, thermodynamic
profiles exhibit little change with even some boost to mid level
lapse rates as the main wave and associated cold pool swing
overhead. Storms may continue to approach severe limits overnight as
a result, especially given the upper level support, but the low
level inversion should limit the main severe threat to hail. Not
expecting showers/storms to end until the shortwave pivots through
Saturday morning, so another concern will be flooding as some
locations could see several rounds of heavy rainfall. The broader
QPF footprint is likely to range between 1-1.5", with localized
higher amounts possible should any training storms develop.
Speed at which the wave and surface cold front pivot out of
southeast Michigan will determine additional convective potential
Saturday. Some guidance suggests the baroclinic zone/theta-e axis
will linger over southern portions of the cwa through mid day
Saturday, which could trigger additional storms. Considering that
favorable upper level features will still be in place, organized
convection cannot be ruled out again on Saturday until the moisture
axis shifts south of the state line.
Rest of the weekend will be characterized by pleasant conditions as
low amplitude ridging and northwest flow maintain seasonable
temperatures. The next system arrives early next weak as a compact
Pacific shortwave approaches the Great Lakes.
MARINE...
A weak cold front settles through the central Great Lakes this
afternoon before stalling across the southern Lakes tonight.
Scattered showers and isolated thunderstorms will continue to be
possible this evening mainly south of Port Austin. Dry conditions
with light winds follows for early Friday as high pressure builds
into the region. The next low pressure system arrives from the west
late Friday afternoon, bringing the front back northward as a warm
front with scattered to numerous showers and storms developing.
Southeast winds will increase ahead of this front late Friday, then
shift to the west Saturday morning as the system`s cold/occluded
front moves through. Gusty winds to 20 kt will be possible for
northern/central Lake Huron through Saturday before the system moves
out, leaving high pressure to build back in on Sunday. The next low
pressure system will likely impact the region Monday into Tuesday.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....CB
DISCUSSION...MV
MARINE.......TF
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
646 PM CDT Thu Aug 10 2023
...Updated 00Z Aviation...
.Discussion...
Issued at 407 PM CDT THU AUG 10 2023
Key Messages:
- Friday Morning Thunderstorms Northern Missouri
- Strong To Severe Storms Friday Late Afternoon
- Heat Index Values Above 100 Along and South of Interstate 70 Friday
Discussion:
H5 ridging today provided clear skies at the start. Daytime heating
though provided enough destabilization in the boundary layer to
develop cumulus clouds across much of the region. Without any
forcing nearby though the cumulus have been inhibited from becoming
deep enough to precipitate across the area. The rest of the
afternoon will feature more of the same, conditions begins to change
tonight.
There is a stronger PV anomaly located over western Alberta
with a stronger vort max associated with it. This has been working
to de-amplify a few ridge axes across the north-central and central
CONUS over the past 6 hours, and will continue to do so heading into
the evening. A few short-wave perturbations have emanated downstream
in the H5 flow. The first area of enhanced vorticity is currently
located over central Nebraska where cloud cover has been increasing.
This will move toward northeast Kansas and northern Missouri during
the overnight hours, and will increase kinematic forcing by the
early morning hours of Friday. Meanwhile, there is a developing
surface cyclone near the Texas Panhandle Region that has
strengthened with another short-wave perturbation on the backside of
the H5 594dam high. The stronger dCVA has allowed the surface
cyclone to deepen, and will be turning flow lower-level flow
southerly into the forecast area overnight. This will increase
dewpoints overnight and increase instability. HREF mean values for
MUCAPE during the early morning hours of Friday are around 1500
J/kg, with maximums around 2250 J/kg. RAP/HRRR soundings indicate a
low-level inversion developing ahead of the nose of WAA. However,
mid-level lapse rates will be near 8.0 C/km, along with stronger
deep layer shear. 0-6km bulk shear values will be near 40-45 kts.
With convection being elevated, expect storms to realize about 30-35
kts. These thermodynamics and deep layer wind shear may help to
sustain updrafts. The limiting factor is that the overall forcing
and convergence does not appear overly strong. A stronger low-level
jet could help increase moisture convergence though. HRRR simulated
convection is more scattered in nature (based on simulated
reflectivity), but perhaps could become more widespread dependent on
the strength of the LLJ and insentropic ascent ahead of the WAA. The
HRRR along with other CAMs seem to favor forcing closest to where
the mid-level vorticity maximum tracks, and this is mainly north of
Hwy. 36. Storms will move east-southeast along the this weak trough
axis. While the hodographs in northeast Kansas and northern Missouri
demonstrate a moderate degree of curvature, most of this is confined
closer to the surface. Elevated storms Friday morning will
experience the portion of it that is straight. The magnitude of the
shear the shear can support stronger updrafts, thus would expect the
primary hazard with early morning convection to be hail around
quarter size. Perhaps a few concentrated wind gusts are possible,
but HRRR/RAP soundings indicate stronger static stability within the
boundary layer, which would make it hard for stronger wind gusts to
reach the surface. Most of the CAM solutions have elevated
convection and the weak short-wave exiting the eastern portion of
the forecast area by 12-13z Friday morning.
In the afternoon, the main PV anomaly will be moving through
Manitoba. There is another short-wave with a stronger vort max that
develops with this and moves out of the northern Rockies and into
the Central Plains by the late morning hours. Meanwhile, the surface
cyclone over the Texas Panhandle continues to strengthen, enhancing
flow through about 700mb and also resulting in surface troughing
that extends into the southwestern Ozarks. This will push a warm
front northeastward and increase WAA through the afternoon. The flow
will bring in additional moisture from the Gulf Region, which will
send dewpoints back into the lower 70s. Expecting to see
temperatures climb through the day, especially south of Interstate
70 where skies should be clearer removed from the morning convection
in northern Missouri. Temperatures are progged in the mid 90s for
our southern forecast area, with NBM 25th-75th ranging between 93
and 100 degrees. Therefore, heat index values will reach between 103-
107 in our southern counties, and have issued a Heat Advisory for
that area. For counties along and just north of Interstate 70,
confidence is a bit lower because we may see increased cloud cover
with the weak trough from Friday morning. Ensemble probabilities are
similar for areas near Interstate 70, but am concerned most of the
members may be underestimating the cloud cover potential. Heat index
values further north, including the KC Metro, still could push the
100 degree mark, but could struggle to reach advisory criteria. Will
allow the next shift to further assess 00z guidance from this
evening and determine confidence in heat issues closer to Interstate
70. The second story to Friday afternoon will be the potential for
additional convection late in the afternoon and into the evening.
Compared to Friday morning, forcing across the region should be
better with warm front advancing northward, strong mid-level vort
max, outflow boundary potential, and differential heating
reinforcing the warm front or convergence along the outflow
boundary. Theta-e advection on the southern part of the boundary
will likely increase SBCAPE to nearly 3000 J/kg per 12z HREF mean.
Assuming cloud cover stays north of Intestate 70, model soundings
are mixing out the boundary layer enough to result in lapse rates
near 8.5 C/km, with mid-level lapse rates around 7.7 to 8.0 C/km.
There will likely be a weak inversion due to the previous passage of
the warm front, presenting CINH around -50 J/kg. But there should be
enough forcing to overcome it, if mixing does not completely erode
the cap by the afternoon. The CAMs are in decent agreement in
simulating convection initiation between 21-23z along the thermal
boundary, mainly between Interstate 70 and Hwy. 36. There may be
some isentropic ascent shower activity further north. The
thermodynamic environment will be supportive of stronger updrafts,
and closer to the mid-level vort max and surface thermal boundary is
where the HREF updraft speed maximums are located. This also lies
along an axis of stronger surface pressure falls with troughing
extending from the cyclone over the Texas Panhandle. As the nose of
the H5 wind maximum reaches the area, 0-6km bulk shear will increase
to around 45 kts. Overall, hodographs will be quite lengthy from
eastern Kansas and across most of Missouri. At the start of the
afternoon, the lower portions of wind profile will not have a lot of
cyclonic shear, however, 3-6km hodographs will start to have a bit
more curvature as the mid-level vort max approaches. The overall
magnitude of shear along with the increasing directional changes
will be capable of supporting a supercell storm mode. At the onset,
if the low-level winds have not completely backed and keeps 0-1km
shear lower while storms are discrete with higher shear above, this
may foster larger hail growth. With LCLs at the start of CI near
1000m, downdrafts with discrete convection will have time to become
greatly negatively buoyant, presenting a threat for damaging winds.
At the onset, the tornado threat for our forecast area looks lower,
as at the time of forecast CI most of the low-level vorticity would
be more crosswise. The higher LCLs also would make it difficult for
tornadoes. Heading into the start of the evening, expecting a low-
level jet to develop that will start to increase 0-1km shear and
provide more cyclonic curvature in the lower-levels while further
lengthening the hodograph. 0-1km SRH should start to increase as
this happens, and may help to favor low-level mesocyclone
development, while increasing streamwise vorticity especially along
the boundary. However, as the LLJ kicks in, if there are multiple
storms around, they may quickly congeal and end a discrete storm
mode. Therefore, this would make it difficult for a tornado threat
to materialize over eastern Kansas and into Central Missouri. Lower
portions of the model soundings still indicate steep boundary layer
lapse rates with strong theta-e deficits, thus a congealed storm
cluster could still produce a strong cold pool and present a
damaging wind threat. Mid-level lapse rates will remain around 7.7
to 8.0 C/km, which could still support larger hail even if storm
mode does not remain discrete. Eventually the for the mid-level vort
max pushes east-southeast out the area, and most CAMs simulate
convection exiting our forecast area in the 02-03z timeframe.
Saturday, short-wave trough clears the area. The 594dam H5 high over
the southern Plains shifts eastward and provides subtle height rises
over area, which only returns us to more zonal flow. However there
is another trough dropping out of the Northern Rockies, and at the
surface the response is to return flow southwesterly once again.
Therefore, with no true cold front, temperatures only drop a few
degrees on Saturday with the previous night`s convective activity.
Attention then turns to Sunday as a positively titled trough moves
across the middle Missouri River Valley and into the western Great
Lakes Region. A high theta-e airmass will still likely be in place
across the area that will provide more energy for active showers and
thunderstorms. Strong instability with shear associated with the
vort max will present another opportunity for organized severe
weather potential. Ensemble probabilities continue to favor SBCAPE
values in excess of 1000 J/kg, and values about 2000 J/kg may become
possible. Will note that in a few of the ensemble members, the
trough is simulated to close off. If this happens, this will create
more uncertainty with the track of the best forcing across the area,
as well as how the ridge in the south may try to push it northward.
Be prepared for active day Sunday, and activity could continue into
Monday.
&&
.Aviation...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 642 PM CDT THU AUG 10 2023
VFR conditions are expected to persist through the period.
An area of showers and thunderstorms is expected to pass north of
the terminals overnight tonight. Residual cloud cover and
variable winds from storm outflow are anticipated through the
morning hours. Another round of showers and thunderstorms is
expected activity expected to start just outside this period.
There is some uncertainty on timing which may result in storms
initiating a little earlier.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...Heat Advisory from noon to 8 PM CDT Friday for KSZ057-060.
MO...Heat Advisory from noon to 8 PM CDT Friday for MOZ043>045-053-
054.
&&
$$
Discussion...Krull
Aviation...Pesel
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1035 PM EDT Thu Aug 10 2023
.SYNOPSIS...
Mainly afternoon and early evening shower and thunderstorm chances
should linger over the region this weekend and into early next week.
Temperatures over the weekend will be above normal with Sunday
afternoon temperatures feeling like 100 to 105 degrees for areas
along and south of Interstate 85. A weak cold front moves in on
Monday with greater chances for rain.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 1030 PM EDT Thursday: A weak frontal boundary continues to
drift across the CFWA from north to south. This was enough to
initiate a few showers along the NC/SC border, but most of the
activity has fizzled. A few northwest flow showers continue to stream
across the NC/TN border. Updated PoPs and temperatures based on
current observations and trends per hi-res models. The forecast
remains on track at this time.
Otherwise, the front will continue pushing thru and stall just south
of the FA, then lift north into the Upstate during the day Fri. The
HRRR is an outlier with a possible morning MCS traversing along this
bndry btw 12-16z, so have given more weight to other less active and
drier models. By the afternoon, the stationary bndry will likely
become activated and begin to produce showers and thunderstorms
mainly across the SC zones. With deep saturation, instability will
be hard to come by, yet the latest NAM is showing arnd 1100 J/kg by
the later afternoon. There exists a possibility of training cells
and with PWATS nearing 1.9 inches, isolated hydro issues may arise.
With persistent cloud cover, esp south, max temps shud be held abt 5
degrees below normal. Dewpoints will reach arnd 70 F in sw/ly flow,
so muggy conds will be in store.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 150 pm EDT Thursday: The upper air pattern over the Conus will
flatten during the short term, with a de-amplifying trough moving
away from the East Coast, and the subtropical ridge attempting to
build into the Southeast. The result will be rising heights and
increasingly hot conditions over the weekend, with max temps
expected to reach the mid-90s across much of the Piedmont by Sunday.
Afternoon Heat Index concerns will be the primary short term hazard,
with some potential for Heat Advisory criteria being met, especially
Sunday afternoon. In terms of the convective potential, diurnally-
driven showers and storms will be sparse on Saturday, as forecast
soundings continue to indicate capped and/or high/unattainable LFC
conditions. In fact, better chances may exist overnight Sat/early
Sunday, as convection originating from a frontal zone draped across
the Ohio Valley and vicinity could make a run toward the southern
Appalachians w/in W/NW deep layer flow. However, PoPs are limited to
the 20-30% range and confined to the mountains for the time being.
Forecast soundings look a bit more favorable for deep convection on
Sunday, and it looks like a more typical mid-summer diurnal cycle
can be expected, with widely scattered showers and storms over the
mtns and foothills, and isolated activity over the Piedmont.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 200 pm EDT Thursday: The pattern will re-amplify significantly
atop the East early in the period, as a significant short wave
trough/evolving upper low migrates from the northern Great Plains at
the start of the period, to New England by the end of Tuesday.
Associated frontal zone is forecast to cross our region during the
Mon/Tue time frame, although timing differences are beginning to
emerge among the major global models, with the ECMWF being
considerably slower with progression of the upper trough/front.
Either way, the approach of the front will enhance the potential for
convection to move into the forecast area from upstream, while
conditions should be favorable for at least diurnal convection Mon
afternoon. Solid chance PoPs are therefore carried over the mtns,
with low chances across the Piedmont Mon afternoon. Considering the
evolving timing uncertainty, 20-30 PoPs are also carried into
Tue.
Beyond Tue, chances increase that a low theta-E air mass will settle
over the Southeast and Mid-Atlantic, largely bringing a temporary
end to convective chances, although the most token of small PoPs for
diurnal convection are carried Wed afternoon and again Thu
afternoon. Hot conditions begin the period, with above-normal
temperatures expected Mon, with temps expected to settle to
slightly-below-normal levels during the latter half of the
extended.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: VFR conditions expected through this evening
for all terminals. Guidance continues to hit vsby/cig restrictions
hard, mainly across the NC mountains/foothills. Thus, have included
IFR to LIFR restrictions for KAVL and KHKY around daybreak Friday
and handled this with a TEMPO. Inconsistent trends regarding shower
and thunderstorm activity for Friday continues. There is an uptick
in coverage per model guidance with timing variations. Decided to
throw in a PROB30 for TSRA and associated restrictions mention at
all TAF sites from mid-morning through the afternoon hours Friday,
depending on location. Best chances will be in the Upstate sites, so
placed VCTS in the prevailing line to best capture the potential,
but timing remains an issue. Winds will generally be out of the
southwest at all terminals on Friday, while KAVL maintains more of a
south-southwesterly component, but could toggle between
northwesterly later in the TAF period.
Outlook: Daily shower and thunderstorm chances with associated
restrictions will continue late this week into the weekend. Fog/low
stratus restrictions will be possible each morning as well,
especially in the mountain valleys.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...DEO
NEAR TERM...CAC/SBK
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...CAC
Area Forecast Discussion
National Weather Service Gray ME
1145 PM EDT Thu Aug 10 2023
.SYNOPSIS...
A cold front crosses the area tonight bringing scattered
thunderstorms across New Hampshire and Maine this evening.
Northwest flow prevails tomorrow, which will clear skies and
bring cooler, but windier conditions to northern New England.
Winds slacken tomorrow night with radiational cooling occuring
Saturday morning. Pleasant weather is expected on Saturday, with
clouds thickening Saturday evening. Scattered thunderstorms
move into the area on Sunday. A more significant system crosses
the region on Tuesday, though timing is very uncertain at this
time.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
1145 PM Update...A north to south band of moderate rain with
embedded thunder is now moving swiftly across the area with the
back edge quickly approaching the NH/ME border. Have mainly
adjusted PoPs to better align with this trend. Brief bouts of
heavy rain will still be possible with this band as it moves
through western Maine and will clear eastern zones before
daybreak. No additional changes were made to QPF with
additional amounts generally around an inch possible near the
coast over a 3 hour period. Behind the band of rain fog will
likely develop and last until sunrise.
810 PM Update...No major changes to the going forecast with the
main focus on refining PoPs and tweaking QPF based on latest
runs of hi res guidance and upstream observations. A band of
mostly moderate rain is moving across VT with some embedded
thunder and observations suggest this rain is generally falling
at rates less than 0.5 inch per hour. Instability is low and
latest RAP analysis suggests ML CAPE will remain below 500 J/kg
with PWATs less than 1.5 inches. Have slightly bumped up QPF in
Grafton County to around an inch and along coastal Maine with
these two areas being highlighted as where some locally higher
amounts may occur overnight. Overall, given the relative low
PWATs and lack of instability the concern for hydro issues is
low and will continue to monitor any areas that see repeated
rounds of heavier bouts of rain.
448 PM Update...Have increased PoPs across the western Maine
foothills where some thundershowers have developed and persisted
longer than hi res guidance has suggested. These showers have
put down a quick half inch of rain, but are moving along at good
enough clip to mitigate hydro concerns. Have also made some
minor adjustments to PoPs through the first part of tonight
based on some of the incoming 18Z guidance without any
significant changes to the going forecast. Overall convective
parameter space suggests any additional storms will likely stay
below severe thresholds and will mainly be watching for areas
that may see repeated rounds of heavy downpours through tonight.
Previously...
A cold front crosses the area tonight bringing showers with
embedded thunderstorms across the area. The line of storms is
about to cross into Vermont as of 3:30PM and will likely make
its way into Maine around sunset. The regional models have
backed off quite a bit on the precip amounts in the last runs so
we opted not to issue a flood watch, however I can`t rule out an
isolated flood advisory if an area gets run over by several
cells. This front looks to be quick moving with good dynamic
forcing for low-level frontogenesis. In terms of the severe
threat, this front will be passing in the late
afternoon/overnight hours, offset from the diurnal instability
trend and therefore limiting the potential for severe storms.
Showers taper off after midnight as dry air starts to make its
way in, however low level moisture from the recent rainfall will
likely create patches of fog tonight.
&&
.SHORT TERM /6 AM FRIDAY THROUGH 6 AM FRIDAY/...
After the sun rises tomorrow morning, mixing will quickly set in
allowing fog to lift out making for a pleasant yet breezy day.
Westerly flow sets in through the day bringing breezy winds
gusting up to 25-30 mph before high pressure starts nosing in
towards the end of the day. Seasonal temperatures are expected
with highs in the upper 60s to low 80s north to south under
sunny skies. Some upslope showers may linger in the morning
north of the mountains, however these should clear out by the
afternoon. Cooler air fully sets in tomorrow night as
temperatures fall into the 50s ahead of another front approaches
for the weekend.
&&
.LONG TERM /FRIDAY THROUGH THURSDAY/...
After a cold front swipes the region Friday afternoon, high
pressure should briefly build in from behind. Saturday morning
will start cooler, as calm winds and clearer skies provide the
opportunity for radiational cooling. Increasing cloudiness
associated with an incoming shortwave could help keep
temperatures cooler through the day on Saturday.
By Sunday morning, the aforementioned shortwave arrives in
northern New England. Some isolated to scattered thunderstorms
cross the region overnight. Modest CAPE (700-1500J/kg) and DCAPE
(~500J/kg) values indicate some gusty winds could be possible
with developing storms. QPF clusters show the most rainfall
likely falling across northern NH and north of US2 in western
Maine. This system poses a low risk of significant impacts to
the region.
Drier air briefly moves through the region on Monday before another,
more concerning system arrives by the end of the day on Tuesday.
Confidence is somewhat high for the existence of Tuesday`s system,
but guidance is quite uncertain with timing. A dynamic low
pressure system over the Great Lakes could occlude and deepen as
its fronts work its way into the Northeast. A southerly low-
level jet over New England at 850mb will provide ample moisture
to work with. PWATS appear to be in the 1.5-2 inch range for
this event. Heavy thunderstorms could set up and put down a
rather significant amount of precipitation. With this in mind,
this system has potential to bring flooding to the region.
Ensembles show a widespread of arrival times, from as early as
Monday night and as late as Tuesday afternoon. The timing of this
system will be crucial to determine the types of impacts expected. A
Tuesday afternoon outcome would likely include some sort of
severe weather threat across the region, while that likely would
not be the case if the storm moved through the overnight hours
on Monday.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
Short Term... Ceilings thicken and lower tonight as a cold front
crosses the area bringing gusty winds and heavy rain with
embedded thunderstorms. A brief period of TSRA restrictions is
likely for most terminals tonight. Clearing sets in tomorrow
morning with most areas returning to VFR through the short term
period.
Long Term...
Generally VFR Flying conditions expected through the day Saturday.
Isolated thunderstorms Sunday could bring VIS and CIGs down in some
spots. LEB, HIE and AUG are the most at risk for flight restrictions
during the day Sunday. VFR flying conditions expected for Monday
with significant reductions on Tuesday and Wednesday, down to
IFR/LIFR as heavy rain and thunderstorms cross the region. Flight
conditions should recover by the end of the week.
&&
.MARINE...
Short Term... A cold front will cross the waters tonight
bringing showers and gusty winds overnight as it passes. Breezy
winds then continue tomorrow as skies clear and flow shifts
from the west. High pressure then settles over the waters for
the first part of the weekend before another round of showers is
possible.
Long Term...
Variable winds around 10kts Saturday, shifting to southerlies
at 10-20kts on Sunday. An isolated thunderstorm or two is
possible Saturday night. Winds then shift to westerlies by
Monday morning at around ~10kts. Wave heights of 2-3 feet are
expected, with a few 4 foot waves possible farther away from
shore. Southeasterlies are likely on Tuesday with the passage of
a large scale system. At this time, at an SCA is possible with
a few gusts of 20kts expected. Wave heights of 3-5 feet are
expected in the open water Tuesday and Wednesday, with 1-4 feet
wave heights possible in Casco and Penobscot Bay. Winds slacken
and shift to westerlies at ~10kts for Wednesday-Friday.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
SYNOPSIS...Palmer
NEAR TERM...Schroeter/Thunberg
SHORT TERM...Thunberg
LONG TERM...Palmer
AVIATION...Palmer/Thunberg
MARINE...Palmer/Thunberg
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
926 PM EDT Thu Aug 10 2023
.SYNOPSIS...
Weak high pressure keeps the end of the work week dry
before showers and thunderstorms return Friday night through Saturday.
A more impactful system is forecast to move into the region on
Monday, bringing renewed storm chances.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Added low-end PoPs across west-central and central OH late
tonight based on recent HRRR updates. These runs show isolated
showers along and ahead of a nearly stationary frontal boundary
draped from Cleveland back through Chicago. Outside of these
rather unimpressive-looking showers, expecting a quiet August
night with perhaps some river valley fog from northeast
Kentucky into south-central Ohio.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
A weak ridging and associated surface high will still be the
primary weather influencer as we head into Friday. However, the
next shortwave is close on its heels and begins to move
southeast toward the area during the day on Friday.
At the surface, a loosely organized, open-wave phase low moves
east toward the Great Lakes region and the ILN area ends up in
the warm sector of this disturbance, which promptly returns
southerly flow near the surface. Temps/Tds echo this by
rebounding back into the mid/upper 80s (temps) and uppers 60s
(Tds) on Friday. In conjunction with this, showers and storms
may be forced out ahead of the main disturbance Friday evening into
the Saturday early morning hours, as a LLJ rounding the parent
disturbance nudges into our northwestern counties. Overnight
lows into Saturday only fall to the upper 60s.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
On Saturday morning, broad troughing will exist to the north of the
Great Lakes region, with ridging over the southeastern states. This
will create a generally west-northwesterly upper flow pattern across
the Ohio Valley, with a respectable height gradient as a result of
the features to the north and to the south. The pattern will only
undergo some occasional incremental changes through the long term
period, with this generally active flow pattern expected to continue
well into next week.
The first chance for active weather within this pattern will be on
Saturday, as a weak wave within the upper flow traverses the region,
and a cold front moves into the Great Lakes -- though the front may
never make it all the way southward through the ILN forecast area.
It is possible that there could be multiple rounds of storms, as
early morning convection upstream of the area may move in during the
morning hours. Additional storms could then develop in the
afternoon. This is the most uncertain part of the forecast, as
morning activity could have an impact on what happens in the
afternoon. However, if morning storms do not adversely impact the
environment, the overall scenario will be favorable for some severe
weather on Saturday afternoon and evening. Both shear and
instability appear sufficient for a severe threat. However, forcing
is another source of uncertainty, as the upper wave is not
particularly strong -- and the cold front will likely be well to the
north. PoPs will be kept in the chance range with this forecast,
until a better handle on storm timing/coverage becomes clear.
A much stronger wave (possibly a closed upper low) will be moving
into the Great Lakes on Monday. A surface low may also accompany
this feature, likely moving eastward across Michigan. There is high
confidence in showers and thunderstorms moving through the area on
Monday, and the wind shear parameters are certainly quite favorable
for severe weather -- especially for August. Uncertainty with this
part of the forecast appears tied to two factors -- timing (models
are not in great agreement) and the possibility of widespread rain
limiting instability. The forcing and shear would suggest some
hazardous weather could occur, particularly if the timing ends up
near peak diurnal heating on Monday. SPC has a portion of the area
outlooked on Day 5 for this threat.
An expansive area of surface high pressure will likely bring drier
conditions to the area for Tuesday and Wednesday, though some model
runs indicate that the flow over the Great Lakes may remain active,
so there could be some chance of precipitation by Wednesday or
Thursday. For now, the forecast will be kept mostly dry.
Temperatures should get well into the 80s on Saturday and Sunday,
though the forecast on Saturday is a little bit uncertain due to the
convective potential described above. For Monday, showers and storms
may keep temperatures slightly cooler, but behind the Monday system
(which does include a potent cold front) Tuesday looks to be the
coolest day of the extended period.
&&
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
VFR conditions will continue at most sites through the period.
Only exception could be some patchy fog at LUK and perhaps ILN
early Friday morning. Have included in LUK`s TAF due to higher
confidence.
Otherwise, expect the next disturbance to slide southeast out
of the Great Lakes late Friday. While precipitation/storms may
hold off until after the TAF window, expect there will likely
be increasing cumulus after 18Z during max heating.
OUTLOOK...Thunderstorms possible Friday night and Saturday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...CA
NEAR TERM...
SHORT TERM...CA
LONG TERM...Hatzos
AVIATION...
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
913 PM CDT Thu Aug 10 2023
.SYNOPSIS...
Issued at 908 PM CDT Thu Aug 10 2023
After a pleasant and dry night with low temperatures in the mid to
upper 60s, warmth and humidity will increase tomorrow ahead of the
next storm system slated to slide through the area early Saturday.
Multiple rounds of storms will move through central Illinois
tomorrow, with the strongest of them capable of localized damaging
winds and hail.
&&
.UPDATE...
Issued at 913 PM CDT Thu Aug 10 2023
Current forecast is on track this evening. Mostly clear skies will
continue overnight with clouds increasing during the early morning
hours due to a complex of storms moving into the CWA. All models
have some precip moving into the CWA tomorrow morning and also are
in good agreement on timing. The only differences are in the
intensity of the storms and how far south they will extend. Based
on new guidance, current forecast/grids look good. Did clean up
pop/wx grids for tomorrow, but messaging is still the same...so no
major update planned at this time.
Auten
&&
.DISCUSSION...
Issued at 203 PM CDT Thu Aug 10 2023
------------------------- [Key Messages] -------------------------
1. 60% chance for thunderstorms tomorrow morning. These storms may
become severe as they move southeast into the afternoon.
2. Another round of severe thunderstorms will be possible Saturday
afternoon if the front hasn`t cleared our area by then.
3. Additional chances for storms late Sunday. Severe potential still
uncertain.
-------------------------- [Discussion] --------------------------
Mid level water vapor satellite shows the next weather maker on tap
is all the way out in the high Plains, but the deterministic ECMWF,
CMC, and GFS each suggest this system will be a fast mover, and
will arrive here Friday morning to produce some storm activity.
As moisture transport increases ahead of this shortwave 500mb vort
max, we`ll find ourselves increasingly unstable with steepening
mid level lapse rates (~7-7.5C/km) by late morning tomorrow, which
suggests that if these storms do in fact hold together, as the
CAMs are currently suggesting, we could find ourselves dealing
with a hail risk with the strongest updrafts. The linear storm
mode could limit the chances of this hazard somewhat (by reduction
in area of moist/unstable air surrounding individual updrafts),
but then there`s also the risk for gusty to damaging winds once
the storms become surface based given model-forecast DCAPE values
over 1200 J/kg with soundings suggesting steep low level lapse
rates and ample mid-level dry air for entrainment and
evaporational cooling for downburst initiation. In addition, the
HRRR is suggesting this line will re-intensify as it drifts
southeast into the I-70 corridor, where it has the line splitting
into cells which it suggests will develop 48+kft cloud tops by
around 1-2 PM. Meanwhile, the NAMNest suggests that line will fall
apart but then leave in its wake an outflow boundary which will
act as a focus for renewed convection during the late afternoon;
this may be an even worse scenario as dewpoints climb into the
upper 70s to produce 4000-5000 J/kg of MUCAPE which, together with
0-3km helicity over 250m^2/s^2, will result in 7+ supercell
composite values conducive to intense discrete cells capable of
all (i.e., wind, hail, tornadoes) hazards.
The parent upper trough is progged to be nearest to us to provide
the best kinematics for sustained convection early Saturday morning,
hypothetically when thermodynamic profiles are less conducive to
severe weather. Nonetheless, we`ll be on the lookout for severe
weather with the first wave late Friday morning-early afternoon
(mainly east of I-57), with the possible second in the
afternoon/evening, and with the possible third on Saturday
- particularly if the front slows or stalls before clearing our
area which is often an issue with systems that approach us like
this one (i.e., with the best forcing well to our north and a
weakening cold front arriving from the north/northwest). The CSU
MLP has the severe risk coming down from 15% wind+hail and 2%
tornado to 5% wind+hail from Friday to Saturday.
In other news, it`ll be quite the uncomfortably humid and warm day
tomorrow, and, depending on cold frontal timing, perhaps on Saturday
as well. The CAMs are suggesting dewpoints in the mid to upper 70s,
which, based on how their dewpoints were underforecast during our
heatwave a few weeks ago, could even be a few degrees underdone.
So, with temperatures in the upper 80s we`re likely to have heat
indices in at least the mid to upper 90s, and possibly low triple
digits, outside of storms.
Then all eyes turn to the Sunday system. From the NAEFS, IVT values
of 500-700 kg/m/s are forecast as a 2sd above-climatology positive
(i.e., westerly) zonal component of the 700-500mb wind arrives
across our CWA ahead of the deepening upper trough. Unsurprisingly,
the EPS mean brings PWATs to around 2 inches, or 150% of climatology
(above the 90th percentile from KILX soundings), across our
southeast Sunday night-early Monday, giving us reason to further
investigate heavy rain potential for possible hydrological/flooding
issues. A NAM forecast sounding from near the Illinois River at 00z
Monday shows a deep warm cloud layer, but fortunately also Corfidi
upshear vectors in excess of 30 kt which should damper the
flooding risk somewhat - making it conditional on training of
storms rather than backbuilding or slow storm motion. The
hodograph for that time period is a bit of an arc as winds veer
quickly with height in the lower levels, from southeast at the
surface to southwest at h85 and west at h7, so it appears that
with EBWD of 50-60 kt instability could actually wind up our
limiting factor for severe potential with generally <2500 J/kg
MUCAPE. We`ll keep an eye on this one, but at this time it appears
the best overlap in instability, shear, and a forcing mechanism
(i.e., the cold front) will be to our west where SPC has a 15%
contour for D4.
While early next work week is looking quite cool in the wake of the
trough with strengthening cool advection bringing 850mb temps to sub
10 degC across our north Monday night, at least according to the
deterministic models, uncertainty in even the upper pattern becomes
significant towards midweek. NBM probabilities for high temperatures
greater than 80 degF fall to only around 50% on Monday and Tuesday,
but further out the 10th to 90th percentile range for probable maxTs
from NBM grows, becoming as large as 78 to 92 degF by Friday in
Springfield. Even on Wednesday, one cluster, comprised of 20% of the
LREF GE, has an expansive ridge across the western 2/3 of the
country; another, made of 27% of the GE, has a shortwave ridge
across the Ohio Valley and trough across the northern High Plains;
clusters 3 and 4, in contrast, have near normal heights over central
Illinois as we`re sandwiched between a trough to our north and
ridge to our south. Given we`ve got a couple potentially strong
systems expected to pass through the region between now and early
next week, model predictability will just be a struggle, and we`ll
need to take each day at a time with the forecast, though at this
point it`s looking like early next week could be somewhat fall-
like.
Bumgardner
&&
.AVIATION... (For the 00z TAFs through 00z Friday Evening)
Issued at 624 PM CDT Thu Aug 10 2023
VFR conditions will prevail at all sites this evening and
overnight with only scattered cirrus clouds expected. Convection
will develop well west of the area tonight and move into the area
tomorrow morning and affect all sites. Will have mid clouds
arriving about 2hrs before the convection then will start
convection at the sites and bring vis down to around 4sm with
showers and VCTS. Will keep cigs at VFR levels, but will have some
scattered clouds below 3kft with the showers. Will have precip
just for two hours and then clear everything out at each site
around noon. Could be some CU type clouds around, but for now will
just have broken cirrus for the afternoon hours. Could be some
additional storms tomorrow, but those may hold off til tomorrow
night. Winds will be west-southwest tonight, then southwest
tomorrow. Westerly winds are possible when the storms are moving
through. After storms, winds should become southwest again. Wind
speeds will be light tonight, then increase to around 10 kts
tomorrow. Gusty winds up to around 20-25kts will be possible with
storms and afterwards.
Auten
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Memphis TN
936 PM CDT Thu Aug 10 2023
...New UPDATE...
.UPDATE...
Issued at 926 PM CDT Thu Aug 10 2023
Current satellite as of 930 PM CDT depicts a few cloud shields
over north Mississippi associated with areas of ongoing
convection. There is also an east-west oriented low cloud deck
near the TN-MS state line that will continue to meander all
evening. Overnight, winds are expected to go calm with pockets of
clear skies across much of the area. In conjunction with all the
standing water around from several days` worth of heavy rain, this
is a slam dunk signal for dense fog. the 00Z HRRR run depicts a
wide swath of visibility less than one mile overnight, especially
across northeast Arkansas. A Dense Fog Advisory is now in effect
for much of the Mid-South overnight from 2AM to 8AM Friday. The
eastern and southern extent of the advisory was a bit of a
question mark given the ongoing convection and cloud cover, but
there are a few "hot spots" notorious for fog (Jackson and
Corinth, to name a few) that we wanted to include. Other than the
addition of fog overnight, the forecast is on track.
CAD
&&
.SYNOPSIS...
Issued at 243 PM CDT Thu Aug 10 2023
Additional showers and thunderstorms may develop this afternoon
and evening in northwest Mississippi. A few of these storms could
become strong to severe with damaging winds and small hail being the
main threats. Otherwise, expect a warming trend to begin on
Friday and last through the weekend before a cold front approaches
the Mid-South on Monday.
ANS
&&
.DISCUSSION...
(This evening through next Wednesday)
Issued at 243 PM CDT Thu Aug 10 2023
A quasi-stationary front remains situated over north Mississippi
this afternoon. Behind this front, temperatures remain in the
upper 70s to low 80s. Residual outflow boundaries from this
morning`s convection may aid in convective initiation this
afternoon for portions of northwest Mississippi. Mid level lapse
rates are expected to remain lack luster. However, bulk shear
around 30 kts and SBCAPE values in excess of 2000 J/kg could
allow storms to become strong to severe with damaging wind and
small hail possible. By late evening, convection should wane
across the region.
A warming trend will begin Friday as the upper level ridge slowly
pushes eastward, eventually centering over the ArkLaMiss. A Heat
Advisory has been issued for areas in eastern Arkansas and
northwest Mississippi due to heat index values forecast to reach
and exceed 105F. Additional warming is expected through the
weekend, with Excessive Heat Warnings likely needed by Sunday.
Luckily, this pattern will not last long as an upper level trough
ejects a cold front to the region on Monday.
Behind the front, expect temperatures and dewpoints to decrease.
Highs for the beginning of next week will be in the upper 80s to
lower 90s. Rain chances are likely throughout the week as we
return to northwest flow. It is too early to tell the exact
impacts of rain next week, but be prepared for a wet and unsettled
pattern.
ANS
&&
.AVIATION...
(00Z TAFS)
Issued at 653 PM CDT Thu Aug 10 2023
Primary aviation weather concern remains low stratus overnight. MEM,
MKL and JBR will remain on the cool side of a remnant outflow
boundary/effective cold front across north MS. Current KNQA/TMEM
VAD wind profile data show the low level inversion depth to be
below FL010. It is in this layer that stratus will likely form.
Skies should clear from west to east through late evening, behind
a departing shortwave disturbance. IFR onset should follow shortly
thereafter. Light winds and well above normal soil moisture
should result in IFR/LIFR persistence until the onset of strong
surface heating toward 15Z.
PWB
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Dense Fog Advisory from 2 AM to 8 AM CDT Friday for ARZ009-018-
026>028-035-036-048-049-058.
Heat Advisory from noon to 8 PM CDT Friday for ARZ009-018-
026>028-035-036-048-049-058.
MO...Dense Fog Advisory from 2 AM to 8 AM CDT Friday for MOZ113-115.
Heat Advisory from noon to 8 PM CDT Friday for MOZ113-115.
MS...Dense Fog Advisory from 2 AM to 8 AM CDT Friday for MSZ001>005-
007-008-010>014.
Heat Advisory from noon to 8 PM CDT Friday for MSZ001-007-008-
010>012-020.
TN...Dense Fog Advisory from 2 AM to 8 AM CDT Friday for TNZ001>004-
019>022-048>054-088>091.
Heat Advisory from noon to 8 PM CDT Friday for TNZ088.
&&
$$
PUBLIC FORECAST...ANS
AVIATION...PWB
Area Forecast Discussion
National Weather Service Morristown TN
1028 PM EDT Thu Aug 10 2023
...New UPDATE...
.UPDATE...
Issued at 1019 PM EDT Thu Aug 10 2023
All forecast elements are in great shape tonight. Skies are
mostly clear with the exception of far southern TN. This along
with light winds across the BL and recent rains will allow for fog
to expand rather quickly over the next couple of hours.
Chances of showers are still uncertain tonight. A weak upper wave
should move east overnight with an increase in 900-800mb flow.
This may be just enough to get showers going. The HRRR continues
to show some of this activity moving across our southern zones so
the current PoP forecast looks good.
&&
.SHORT TERM...
(This evening through Friday)
Issued at 301 PM EDT Thu Aug 10 2023
Key Messages:
1. Some showers and embedded thunderstorms are possible
overnight, but no severe weather is expected.
Discussion:
Visible satellite imagery shows some clear low level convergence
just south of a front, along the TN/KY border from middle TN
eastward into the Tri Cities area this afternoon. Some scattered
showers are forming in the vicinity of this low level forcing and
this should continue through late this afternoon before we lose
support from daytime heating. Models forecast the front to slowly
shift south through the evening and overnight hours. Skies should
clear out in its wake, allowing for development of low clouds and
fog tonight especially north of I-40 where copious amounts of
rain have been seen over the last few days.
Later tonight, another shortwave is expected to move by to our
south. There`s mixed reviews on how far north precip associated
with this feature will make it. Some of the latest high res
guidance along with the NBM show rainfall extending north of the
I-40 corridor late tonight and into Friday morning. If the front
makes it to the south end of the CWA tonight, it`s hard to imagine
rainfall making it that far north. Do have some slight chances
extending north of I-40 but believe the focus of rainfall will be
mainly along the TN/GA line and rain chances reflect that.
Otherwise, not a lot going on in the short term which is a welcome
change frankly.
&&
.LONG TERM...
(Friday night through next Thursday)
Issued at 301 PM EDT Thu Aug 10 2023
Key Messages:
1. Multiple rounds of showers and storms are possible from Saturday
through Monday with some stronger storms possible.
2. Hot temperatures are expected through the weekend, followed by
milder conditions next week.
Friday Night through Monday
At the start of the period, a general troughing pattern will be in
place across the eastern U.S. with the upper jet over the region.
There will also be broad and deepening low pressure to our north,
which will increase southerly flow across the eastern U.S. With the
broad southerly flow and increased moisture, much warmer conditions
are expected in comparison to what has been seen in recent days.
Based on the consensus, the combination of WAA and humidity look
sufficient for places in the Southern Valley to reach at least near
heat advisory criteria on Saturday. Another concern for the day will
be yet another chance of convection, potentially widespread. Global
and high-res model guidance all suggest a convective environment
consisting of impressive instability (SBCAPE > 2,000 J/kg GEFS mean)
and fairly weak but non-zero shear. It is certainly difficult to
tell where convection may develop and progress. However, several
solutions are suggesting development to our northwest and
progression into the area by later in the day.
A similar pattern will remain in place on Sunday with variable
indications of shortwaves near the area, possibly in the presence of
decent thermodynamics. By Monday, focus will turn towards a more
robust closed low and developing system along the Northern Tier of
the U.S. This system will likely provide a more sheared environment
than during the previous days. The location and extent of the best
forcing still remain unclear with the best conditions potentially
being near or just north of our area. In any case, the first half of
the extended period looks to remain very active with varied chances
for strong to severe storms and additional rainfall after recent
flooding. Based on these indications, confidence remains too low for
specific messaging any particular day. However, it is likely that
messaging will be needed for a specific day, regarding strong to
severe storms.
Tuesday through Thursday
By mid-week, a drier and more settled pattern is expected as
troughing shifts further to the east and high pressure expands into
the area. Isolated rain chances can’t be completely ruled out, but
most places will likely remain dry for at least a few days. The
advection of drier air will also allow for overnight temperatures to
drop lower than what has been seen for several days.
&&
.AVIATION...
(00Z TAFS)
Issued at 652 PM EDT Thu Aug 10 2023
Main aviation concern tonight will be fog development. Afternoon
CU will gradually diminish with loss of heating leaving mostly
clear skies overnight. Fog is most likely at TRI where LIFR
conditions are forecast. Lesser potential at TYS with only MVFR
forecast, and not expecting fog developing at CHA. Any fog will
scatter out a couple hours after sunrise. However, low CIGS at CHA
is possible as increasing 900-800mb flow develops. VCSH begins
near CHA around 12Z. Elsewhere, confidence in VCSH activity is to
low to mention. Otherwise, VFR is expected to prevail through much
of Friday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 72 87 71 92 / 40 30 10 30
Knoxville McGhee Tyson Airport, TN 69 85 69 89 / 10 20 10 20
Oak Ridge, TN 68 85 70 88 / 10 20 0 20
Tri Cities Airport, TN 66 82 66 86 / 10 20 10 20
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
UPDATE...Diegan
SHORT TERM...CD
LONG TERM....BW
AVIATION...Diegan