Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/24/24
Area Forecast Discussion
National Weather Service Columbia SC
821 PM EDT Mon Sep 23 2024
.SYNOPSIS...
High pressure building over the SE US will keep warm conditions
over the Southeast into the first half of the work week.
Multiple shortwaves crossing the region will bring chances for
precipitation through much of the week. Confidence remains on
the lower side in the forecast beyond midweek as there is still
uncertainty associated with the evolution of an upper trough
moving toward the region and the track of a likely developing
tropical system in the Gulf.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Key Message(s):
- Isolated convection may linger through the near term
Water vapor imagery shows a shortwave working over the top of a
ridge centered to our south. This shortwave will allow
convection to persist through the evening and possibly into the
early morning. The RAP shows elevated instability over the area
of around 1000 J/kg through the night supporting the chance of
thunderstorms. Storm movement will be fast enough to limit the
threat of flooding and stable low levels should prevent wind
gusts.
Light northerly winds at the surface will help advect slightly
cooler air into the northern forecast area. This should yield a
similar setup to the previous morning with low stratus over
northern portions of the area. Temperatures will be mild
overnight with lows in the upper 60s to low 70s.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Key Message(s):
- Upper ridge continues to bring above average temps.
- Marginal Risk for Severe Weather Tuesday Afternoon and Evening
north of Columbia.
The upper level ridge axis will shift slightly eastward Tuesday with
above average temperatures continuing. Models do indicate the
potential for lingering stratus through the morning across the
northern portions of the forecast area once again, so there will be
at least somewhat of a temperature gradient with highs in the low
90s in the south to mid 80s across the north. Bit of a question mark
as to the development of showers and storms Tuesday afternoon as
HREF mean soundings show the potential for a capping inversion
across the area, but also weaknesses in the ridge and some weak
convergence across the northwestern portions of the area. As a
result, isolated to widely scattered showers and storms are
possible with highest coverage in the NW. Some of these storms
may be a bit organized with deep layer shear approaching 30
knots near the SC/NC border. A marginal risk for severe weather
remains in place north of Columbia.
The upper ridge continues to shift eastward Wednesday with a
deepening trough over the lower Mississippi Valley that there
remains good consensus among models will develop into a cut-off low
pressure system. Even some of the faster guidance keeps an impacts
from PTC Nine well to our south through Wednesday. This will lead to
fairly uneventful weather Wednesday with temperatures above normal,
although likely a few degrees cooler than Tuesday and little chances
for rain.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Key Message(s):
- Likely tropical system continues to develop in the Gulf, but
uncertainty remains in its track.
- Chances for precipitation increase toward the end of the week.
National Hurricane Center is issuing advisories on Potential
Tropical Cyclone Nine. High confidence that PTC 9 will develop into
a tropical cyclone in the northwest Caribbean or southeast Gulf of
Mexico and move north towards the Gulf Coast. Increasing confidence
in the storm making landfall as a hurricane but uncertainty remains
in the track as it interacts with an upper low moving in the
Mississippi Valley. Most guidance (global models and ensemble
members) do generally take the center west of the area but exact
impacts depends on how close the center moves towards the area
and the degree of weakening as it moves inland. For now, the
biggest impact will likely be moderate to potentially heavy
rainfall that could develop as early as Thursday afternoon,
although most ensemble members at this point favor heaviest rain
Thursday night. With the current track of the storm, however,
tornado potential as well as strong winds are possible with
ensemble guidance indicated highest potential for gusts above
40mph in the CSRA (around 50 percent chance probability).
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
VFR conditions expected through at least 06z. IFR ceilings at
CAE/CUB developing toward morning.
Scattered to broken cumulus across the area this evening. Radar
indicating a few showers and thunderstorms in the area. Widely
scattered showers moving over an upper ridge may continue into
the overnight as suggested by the HRRR. But based on radar trends,
the showers are not expected to impact terminals at this time.
Low clouds to the north of the area near the SC/NC border are
expected to move south into central SC late tonight. The highest
probability of restrictions appears to be at CAE and CUB. Will
continue previous forecast of IFR ceilings at these sites.
Otherwise, MVFR fog may develop at OGB and AGS toward daybreak.
Focus for showers on Tuesday appear to be north and west of the
area with upper ridging in the area limiting development.
Scattered to broken cumulus/alto cumulus through the day. Winds
mainly south or southwest less than 10 knots.
EXTENDED AVIATION OUTLOOK...Restrictions along with strong
winds becoming possible Thursday through Saturday associated
with a potential tropical system moving west of the forecast
area.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...None.
GA...None.
&&
$$
Forecast Discussion at weather.gov/mqt.
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
MARINE...None.
&&
$$
UPDATE...Huyck
DISCUSSION...Levens
AVIATION...Huyck
MARINE...Levens
Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
628 PM CDT Mon Sep 23 2024
.KEY MESSAGES...
- Light Rain Shifts Eastward Through The Evening
- Light Rain Possible Tuesday Afternoon into Late Evening
- Active Weather Possible Friday Through The Weekend
&&
.DISCUSSION...
Issued at 216 PM CDT Mon Sep 23 2024
Mid-level tough axis is still working its way across our forecast
area, but the bulk of the robust kinematics associated with it have
shifted well east of the area. Surface anticyclone has managed to
move in underneath it, and the cold front has completely moved out
of Missouri and Kansas toward the southeast. Weak mid-level lift
will help maintain the stratus cloud cover and light precipitation
activity through the remainder of the afternoon. Based on radar
trends, this will primarily be east of Interstate 35. The cloud
cover will keep temperatures much cooler this afternoon, generally
in the mid 60s. This trough axis will move east of the Mississippi
River Valley between 08-10z Tuesday morning, and surface anticyclone
should be centered around the eastern Plains. There is a PV anomaly
sitting over the Canadian Prairie Provinces that is expected to drop
another lobe of vorticity into the Central CONUS through Tuesday
morning, while mid-level ridging amplifies over the western third of
the CONUS. This vort max will ultimately provide a closed-low system
that deterministic guidance has been depicting for the last few
days, hanging around the area for most of the weak. Although the
kinematics do not appear overly robust, there is potential for an
axis of weak convergence to setup somewhere along the Missouri River
Valley and eastern Plains late Tuesday afternoon and into the
evening that could generate light shower activity. There has been an
increase in measurable rainfall probabilities from various ensemble
suites late Tuesday into early Wednesday, generally 20 to 30 percent
chances for measurable rainfall, though for a threshold exceeding
0.10 inches those probabilities drop to below 10 percent. Amongst
both CAMs and coarser model guidance, most solutions only produce a
few hundredths of an inch of QPF. Weak instability may develop if
the clouds thin out enough, the HRRR does try to produce activity
that is more convective in nature, but the instability may never get
there, so for right now would expect mostly general rain shower
activity if anything materializes at all.
For the remainder of the week, the mid-level closed-low system will
keep the cooler airmass in place. Most ensemble suites have
converged better on keeping it centered nearly directly overhead of
Missouri, leading to high temperatures mainly in the mid 70s. Most
points in our forecast area have an inner-quartile range between 72
and 76 degrees, with far northeast portions of the area maybe only
seeing the upper 60s through the week. In general, morning low
temperatures will be in the mid 50s. Then aside from the Tuesday-
Wednesday light activity, there is not currently any other robust
signal for measurable rainfall, though will point out that as long
as cloud cover lingers isolated sprinkles cannot be ruled out
through Wednesday and Thursday.
Attention then turns to Friday and the remainder of next weekend.
The mid-level closed-low system should still be parked overhead,
while ridging continues to amplify over the western third of the
CONUS. There is a tropical wave moving through the Caribbean that is
likely to become a named tropical system at some point, which
appears to have a decent probability of coming ashore. However, this
system has not yet fully developed, and at this point still cannot
put any high amounts of trust into medium-range deterministic
solutions. The GFS still tries to depict a mid-level Fujiwhara
effect with the 500mb closed-low and the tropical cyclone sometime
Friday into Saturday. Most atmospheric variables and parameters in
the ensemble output shows you the wide spread in any potential track
as well as intensity of tropical cyclone activity. Inner-quartile
temperature spread for most points in eastern Kansas to Central
Missouri is over 10 degrees, ranging from the the mid 60s to nearly
lower 80s. QPF spread is also large heading into the weekend,
between just a few tenths to nearly 2.5 inches for inner-quartile
spread. And looking at a postage stamp view of 6-hour QPF from
individual members, you can see drastic changes in overall track of
any kind cyclone. With that being said, confidence in any specifics
is very low for the weekend forecast. Probabilities are high for
some kind of measurable rainfall, but with respect to any flooding
concerns and extremes it cannot be determined at this time. In
addition, if we see a tropical airmass move into the area, that
could bring enough instability to generate stronger thunderstorms,
but a more easterly solution could keep our area much more stable
thermodynamically as the stronger kinematics would approach the
area.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 628 PM CDT Mon Sep 23 2024
Conditions overnight will vary from MVFR to potentially LIFR.
Low clouds are splitting eastern KS and western MO with northern
areas seeing higher MVFR to VFR ceilings and low MVFR to IFR
ceilings south. It looks more likely than not (about 60%) that
this line will transition south through the KC area terminals.
But that then allows for the development of fog (~40% chance for
visibility <1 mile) and/or low clouds (~60% chance for ceilings
<1000 ft) to develop/ build back into the terminals. Have added
some mention of fog and low clouds to all sites given the
increased probabilities. These conditions linger into tomorrow
morning with improving conditions late in the morning as winds
increase from the west and eventually northwest.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...None.
KS...None.
&&
$$
DISCUSSION...Krull
AVIATION...CDB
Area Forecast Discussion
National Weather Service Louisville KY
926 PM EDT Mon Sep 23 2024
.KEY MESSAGES...
* Strong to severe storms possible Tuesday, especially in the
afternoon along and east of I-65. Gusty winds will be the main
severe threat, with small hail a secondary threat.
* Drought-easing rainfall in the forecast as the remnants of a
tropical system move into the region Friday. Stay tuned to latest
updates from NHC on the forecast path/strength of this system.
&&
.UPDATE...
Issued at 925 PM EDT Mon Sep 23 2024
Convection is winding down rapidly in the vicinity of a diffuse
front draped east-to-west across Kentucky. Expect a few dry hours
across our portion of the Ohio Valley, but know that the next round
is already in sight with a batch of showers and a few embedded
thunderstorms crossing from eastern Missouri into southern Illinois.
Look for precip to arrive just before daybreak Tuesday, perhaps with
some isolated thunder. The stronger storms are expected Tuesday
afternoon, when we`ll likely have enough instability for a few of
those storms to become severe.
This update will mainly clean up wording to reflect timing of the
next round of showers.
&&
.SHORT TERM /THROUGH TUESDAY/...
Issued at 339 PM EDT Mon Sep 23 2024
This afternoon and Tonight...
The remnants of a cold front remain draped across the region this
afternoon, with waves of showers and storms moving from west to east
along the boundary. Widespread coverage of clouds and precipitation
along and north of I-64 so far today has created a gradient in
heating and instability which splits the FA in two. North of this
gradient, stable conditions should suppress convection at least in
the near term, while greater instability across south central and
southeastern KY (up to 2000 J/kg MLCAPE) will promote additional
convective initiation over the next several hours. A few strong
storms have already developed, and a continued risk for gusty winds
and small hail will continue into the evening hours, primarily along
and south of the western KY/Bluegrass Parkways.
This evening into tonight, the 500 mb trough over the central Plains
will move toward the Mississippi Valley and amplify, strengthening
deep-layer flow over the Ohio and Tennessee valleys. In response to
the upper trough amplification, a LLJ core is expected to develop,
with 35-40 kt SW winds progged over western KY late tonight into
tomorrow morning. This SW LLJ should condition the atmosphere for
additional waves of showers and thunderstorms as PW values maintain
at around 1.6-1.9". Hi-res sounding progs show a stable layer near
the sfc with around 1000 J/kg MUCAPE aloft, so while the risk for
strong to severe storms will be low, thunderstorms with heavy
rainfall and lightning will continue to be possible overnight. With
the rich moist air mass in place, diurnal temperature ranges will
continue to be suppressed, with lows only expected to fall into the
mid 60s to around 70 tonight.
Tomorrow...
Tomorrow, the upper trough will continue to shift eastward, with jet
dynamics becoming more supportive for broad low-level rising motion
as an area of upper diffluence moves into the Ohio Valley. As the
coupled sfc/upper disturbance strengthens, a sfc low will develop
across MO, moving northeast just north of the Wabash Valley during
the day on Tuesday. The sfc front that is overhead today should be
well north of the area by late tomorrow morning, placing the area
within the warm unstable sector. At the same time, strong flow aloft
for this time of year will allow for 35-40 kt of deep-layer shear,
which will be supportive of organized clusters of convection. The
main uncertainty lies in how unstable we can get tomorrow,
especially if we have multiple waves of convection that move through
late tonight into tomorrow morning. As an example of this, 12Z HREF
mean SBCAPE tomorrow afternoon is around 1500 J/kg along and east of
I-65. However, 10th percentile SBCAPE is less than 200 J/kg, while
90th percentile SBCAPE is around 2500 J/kg. As a result, tomorrow`s
severe risk definitely has a significant bust potential, but also
has a relatively high ceiling as well. By the window of peak
instability tomorrow afternoon, surface winds should be fairly
veered across much of the area, so the main severe threat with any
strong storms would be gusty or damaging straight-line winds, with a
secondary threat being small hail. 12Z HRRR neural network
probabilities indicate the greatest threat for damaging winds east
of I-65 into eastern KY, with the peak timing between 18-22Z Tuesday
(2-6 pm EDT). Multiple waves of convection are possible, continuing
until sfc FROPA Tuesday evening. While antecedent conditions will
allow us to receive quite a bit of water without significant issues,
HREF localized probability-matched mean swaths of QPF greater than
2" do open up the possibility for localized flooding issues tomorrow
afternoon and evening.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Issued at 339 PM EDT Mon Sep 23 2024
Busy week ahead as we deal with first a cutoff upper low
meandering across the mid-MS Valley and then what becomes of the
remnants of a well-modelled and still not named tropical system!
Tuesday evening, deterministic and ensemble guidance are in
excellent agreement, placing the center of a 567 dm 500-mb low over
northern Missouri. This location keeps our area in a southwesterly
flow aloft at least for that evening, with a moist environment still
in place. CAM`s respond by keeping in widely scattered storms,
mainly south of the I-64 corridor and east of I-65. As we get
through the day Wednesday, the upper low sinks into the AR/MO border
area, bringing some drier air briefly into our region. Cloud cover
that day still should help limit any available instability, so that
day stands the best chance to be low on pops and relatively cool
high temperatures (near normal for late September). By "low" on pops
I should say that still keeps in some likely-range chances (60-70%)
in our southeastern counties, whereas southern IN and northern KY
stay in the 20-30% range.
For Thursday we see a transition, as the upper low continues its
trek southward but interacts with the tropical system moving ashore
somewhere along the NE Gulf Coast. The GEFS spreads for locations of
the upper low are fairly high, whereas the Euro EPS and GEPS have
more confidence. The latter two ensemble solutions allow more
moisture to get pumped into our region, whereas the GEFS keeps more
of it over the Deep South. That obviously has a big impact on how
much precip we can get into our area, especially as we move into
Friday! Latest NBM guidance looks in line with the grand ensemble
data, both for the daytime period Thursday and getting into Thursday
night.
NBM PoP guidance looks pretty good for Friday/Friday night, given
the current NHC forecast for this systems track...again in line with
pops on the grand ensemble. A little concerned by 12Z GFS solution
showing our area getting gapped...with the remnant center hung up in
the Apalachians and the cutoff low much farther southwest, over the
Arklatex. Again, in line with NHC forecast and 00Z EPS/GEPS and 12Z
CMC/Euro solutions, think NBM guidance pops look pretty good. Will
make an adjustment to wind and wind gusts up from NBM, based on Euro
EPS guidance showing median peak gusts in the 30-40 mph range.
Higher values aren`t out of the question, but trending upward seems
a good bet here.
As far as hydro issues with the rains this week...areal average
rainfall totals for this week/weekend based on current forecasts
look to range from 2-4". This much rainfall on the drought grounds
we have currently would barely bring some of our low-flow rivers in
southern KY up to action stage. It would take 5-6" of rainfall to
get them barely into minor flood stage. So it would seem we can
handle (and we need it!) this much rainfall, but will message the
chance for localized flooding possible.
The weekend and start to next week are a bit more up in the air as
far as confidence, as a lot will depend on distance to the merged
cutoff upper low to our area. Still will hang onto fairly cloudy
skies and even solid chances (30-50%) for measurable rainfall each
day.
Given the moist conditions, expect smaller diurnal temperature
ranges each day this period...with high temperatures near normal and
lows above.
&&
.AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 713 PM EDT Mon Sep 23 2024
Cold front is now draped just south of SDF and LEX, with low clouds
and light easterly winds to the north and mainly lingering
stratiform rains to the south, as the more vigorous convection has
now pushed south and east of the terminals. Main question this
evening is whether low clouds will fill in sufficiently to restrict
cigs. Have gone with borderline IFR/MVFR for HNB, but will keep SDF
and LEX VFR with a mention of few-sct low stratus. Winds will be
light out of the E-SE through the night, then veer to SW by midday
Tuesday as the front waves back north as a warm front.
A couple different waves of precip on Tuesday, with the first from a
weakening MCS in the morning. Can`t rule out thunder but figure the
main impact for most will be rain. Will carry a TEMPO for morning -
SHRA with minimal restrictions.
Warm sector will feature SW winds just over 10 kt with gusts pushing
20 kt in the afternoon. Incoming system will provide enough lift for
at least scattered convection, which will be sufficiently hit-and-
miss to carry only TEMPO groups.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...RAS
SHORT TERM...CSG
LONG TERM...RJS
AVIATION...RAS
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1052 PM CDT Mon Sep 23 2024
.KEY MESSAGES...
- There in a marginal risk for strong to severe thunderstorms
this afternoon and evening mainly across southeast Missouri and
southern Illinois. Damaging winds are the main threat.
- Conditions will clear Tuesday, leaving dry conditions for the
mid- week period.
- Uncertainty remains in the return of rain Thursday through the
weekend.
&&
.SHORT TERM... (Through Late Tuesday Night)
Issued at 207 PM CDT Mon Sep 23 2024
The region is socked in with heavy cloud cover once again today,
stunting temperatures significantly. As of 2 PM temperatures have
struggled to top 70 degrees in most areas. The mass of showers and
thunderstorms that moved into the area this morning have been
steadily moving northeast through the forecast area while another
area of showers is moving into central Missouri. A weak surface low
has developed across southwest Missouri in response to the
approaching mid-level shortwave, with its attendant stationary front
stretched across the Missouri-Arkansas border. As the mid-level
shortwave approaches additional showers and thunderstorms will spawn
across southern Missouri and Illinois this afternoon and evening.
How many develop and how strong they become depends on how much
instability is able to build, which has been limited by the
aforementioned heavy cloud cover. Current RAP analysis shows 500-
1000 J/kg of MUCAPE across the southern forecast area with higher
values across the warm sector south of the boundary. A few
thunderstorms could organize in the 30-40 kts of 0-6 km shear to
become strong to severe this afternoon. Damaging winds would be the
main concern in areas that are able to clear out and mix a little,
but an isolated case of 1" hail also cannot be ruled out.
The best environment for severe thunderstorm development will be
south of our forecast area where greater instability, as well as
enhanced lift and shear from the front will give thunderstorms an
extra boost. In this area, proximity to the front will locally
enhance the tornado potential (2%), despite ambient 10 kt 0-1 km
shear. If the front were to push northward over the next few hours,
these conditions could move into the southern CWA.
Showers and thunderstorms will linger into the overnight hours,
largely across eastern Missouri and western Illinois. With
precipitable water remaining near the climatological maximum for
this time of year (1.50-1.75") and the potential for convective
elements, heavy rain is once again a possibility with individual
thunderstorms. The 3 hourly PMM indicates up to 2 inches of
additional rainfall are possible within the areas of heaviest
precipitation. The progressive nature of the thunderstorms and 3
hour flash flood guidance still near 2-3" will keep flooding at bay,
though ponding of water in low lying areas is expected.
Showers and thunderstorms will linger into tomorrow across the area
as the mid-level trough associated with the previously mentioned
shortwave slides into the region. These are not expected to be
strong as moisture begins to erode with the approach of a surface
high into the mid-Mississippi Valley. Temperatures will begin to
rebound tomorrow from their unseasonably cool values today thanks to
increase insolation and less precipitation, highs will peak in the
low 70s.
Delia
&&
.LONG TERM... (Wednesday through Next Monday)
Issued at 207 PM CDT Mon Sep 23 2024
The mid-level trough will inch southward during the mid-week period,
with mid-level height rises and the advancing surface high keeping
conditions dry. At the same time many ensemble systems point to a
tropical system (Potential Tropical Cyclone Nine) pushing northward
into the Gulf of Mexico. By the start of the weekend the tropical
system is expected to get caught in the mid-level trough`s flow,
increasing moisture advection into the lower and mid-Mississippi
Valleys. The two systems will continue to interact while a Rex Block
sets up over the CONUS. Recent runs have shown a northward shift in
the system, the result is increasing precipitation chances for the
second half of the work week and weekend. As previously mentioned,
many of the ensemble systems depict this scenario, which is
resulting in very high PoPs (70-80%) in the extended period. These
PoPs seem too high given the uncertainty with the development,
strength, and movement of this tropical system, but confidence is
not high enough to make any significant changes.
Temperatures through the week will remain largely near normal.
Although more sunshine and less clouds and precipitation would
prompted more effective warming, particularly later in the period.
Delia
&&
.AVIATION... (For the 06z TAFs through 06z Tuesday Night)
Issued at 1050 PM CDT Mon Sep 23 2024
Expect IFR flight conditions to continue through mid-day Tuesday as
a large area of low-level stratus blankets the region. Isolated
showers continue to be possible overnight at all terminals. Light
winds will favor the development of fog with accompanying reduced
visibilites. Visibilites are forecast to improve after sunrise on
Tuesday morning as winds increase. VFR flight conditions are
expected to return late Tuesday afternoon with northerly winds
persisting.
MMG/Carney
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Raleigh NC
945 PM EDT Mon Sep 23 2024
.SYNOPSIS...
Mid-level disturbances, in moist, southwesterly flow aloft, will
interact with a stalled surface front that will weaken over the
Carolinas through mid-week.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 945 PM Monday...
Consecutive runs of the HRRR continue to support the development of
showers and isolated storms after midnight and expanding in coverage
through the overnight and towards daybreak, However, its has been
relatively inconsistent on placement and have decided to cap most
locations at chance PoP (25-54% chance). Convection is expected to
develop as strengthening low-level WAA and moist isentropic ascent
occurs at the base of an elevated instability axis of 500-1500 J/kg
of MUCAPE. Severe and flooding threat remains low as the surface is
protected by a stable layer beneath the inversion and showers/storms
motions should prevent heavy rain from lingering over any one area
for too long. Most locations where precip occurs, should receive
between a tenth and 0.5 of an inch. Isolated instances of 1-2 inches
may be possible where multiple rounds occur, which most locations
outside of urban areas will be able to handle as flash-flood
guidance in 6hrs is 2.5-4 inches across the Piedmont. Synoptic
pattern and forecast rational remains the same and is discussed
below.
Previous discussion as of 355 PM Monday...
A sub-tropical, 500 mb anticyclone along the Gulf coast will
continue to drift ewd and across nrn FL tonight, while its
accompanying ridge will progress across the South Atlantic states.
Convectively-perturbed, wswly to swly flow will be directed from the
lwr MS Valley to the OH Valley and cntl Appalachians, between that
ridge and a couple of shortwave troughs that will pivot across the
Upr Midwest and mid MS Valley. Cntl NC will consequently remain in
anticyclonic flow and a subsident regime through the mid/upr-levels
through early tonight, after which time the convectively-perturbed
flow will spread ewd and across the wrn and w-cntl Carolinas. Weak
low-level jet development, with ~20-25 kt sswly flow likely at 925
mb, will likely result across the Carolinas overnight. That flow
will be directed nearly perpendicular to a surface front, now
accompanying a weak frontal low over cntl SC, which may retreat
slightly nwd across nrn SC and into perhaps the far srn NC Piedmont
through this evening. WAA related to the LLJ will favor both a
gradual increase in MUCAPE, elevated atop the stable boundary and
stratus layer that has remained in place over the NC Piedmont today,
and also isentropic upglide that will increase the risk of elevated
showers and isolated storms over cntl NC (particularly areas from I-
95 wwd) overnight-Tue morning. Widespread low overcast should
otherwise redevelop in the unseasonably moist/humid regime
characterized by PWs of 1.75-2", with low temperatures in the 60s.
&&
.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 245 PM Monday...
The stalled boundary is forecast to be draped NW to SE from the
southern/western Piedmont, arcing into the southern Sandhills to
start the period. With time, the boundary will lift north as a warm
front during the afternoon and evening, perhaps reaching southern VA
come Wed morning. Aloft, shortwave troughing will be present across
the Mid-Mississippi Valley, while ridging will be over the southwest
Atlantic. The resultant flow will be southwesterly, with a few
disturbances tracking through in the morning, aftn/eve, and
overnight period.
Morning isolated to scattered showers or storms will be possible
across eastern sections of central NC as a disturbance tracks across
the area. The highest PoPs are favored over the Triangle,
east/northeast Piedmont, and into the Coastal Plain. Outside of
these showers, widespread low stratus and patchy fog will be present
north of the aforementioned boundary. As the front starts to lift
north, however, we should see erosion of the stratus from SW to NE,
slowest in the north and northwest. As a result, highs should range
below normal in the mid 70s in the far north, to above normal in the
mid 80s in the S and SW.
Another round of scattered showers and storms will develop in the
late afternoon/evening, continuing into the overnight hours as a
secondary disturbance tracks through. The front and differential
heating will aid forcing for ascent, along with 2000-2500 J/kg of
MLCAPE. A Marginal Risk of severe storms is still in place across
the western Piedmont, owing to deep-layer shear of 35-40 kts and
DCAPE of 800-1000 J/kg, supportive of a damaging wind threat.
Isolated large hail cannot be ruled out as well, given nearly
uniform hodographs in place. CAMs vary on where storms initiate, but
a general consensus appears across the far western Piedmont, before
advancing east-northeast in the evening to overnight. Highest PoPs
are across the NW and Triad and lowest in the SE.
As we go into the late-evening hours, storms appear to become at
least partially elevated, and PW`s upwards of 2 inches (140-percent
of normal) with SW WAA aloft will support a flash flood threat in
training storms atop the lingering boundary. The 12z HREF is showing
a signal for 2-3+ inch rainfall totals in two areas. One area
stretches along and just SW of the Triad into VA, while a second
area stretches along US-1 into the Triangle. Given these two
regions, WPC has introduced a Marginal Risk for excessive rainfall
over much of central NC to cover the uncertainty. Convective
coverage should start to favor northern areas overnight into Wed
morning as the boundary slowly shifts north. Overnight lows will be
in the mid to upper 60s.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 335 PM Monday...
Wednesday and Wednesday night: Aloft, a low will cutoff and meander
over the ARKLATEX region as the northern stream trough continues
eastward through the Great Lakes and Northeast. Meanwhile, high
pressure will ridge northwestward through the Carolinas/lower mid-
Atlantic. At the surface, high pressure over eastern Canada will
ridge sswwd along the Northeast and mid-Atlantic coasts. Meanwhile,
what is currently Potential Tropical Cyclone Nine will lift
northward into the eastern Gulf of Mexico, then is expected to
deepen and move quickly nwd through the eastern Gulf toward the Big
Bend area of FL. An inverted trough will extend nwd from the Gulf to
along the srn/ctl Appalachians, west of the aforementioned ridge, as
another trough extends ssewd through the OH Valley/nrn Appalachians
from a low moving ewd through the nrn Great Lakes. The confluent
sly/sely flow will advect warm, moist air into the area. There will
likely be plentiful cloud cover, which may limit daytime heating and
thus potential instability. The 12Z NAM forecast soundings show
MUCAPE around 1000 J/Kg, effective shear around 30 kts and PWATs in
the 1.5-1.8 inch range across central NC during the aft/eve. Given
the warm, moist, potentially unstable environment, expect any
ongoing showers to continue into the day Wed and cannot rule out
some storms as well. Highs should range from around 80 degrees NW to
mid 80s south with lows mainly in the mid 60s to around 70 degrees.
Thursday and Friday: A Rex Block will set up over the eastern US,
with the low over the ARKLATEX and the low over southeast Canada,
bisected/blocked by a ridge extending nwwd from a high off the
Southeast US coast and another high over the Desert Southwest
ridging newd into the Great Lakes. The other feature at play is
Potential Tropical Cyclone Nine, which is forecast to move inland
near the Big Bend area of FL on Thu, lift nwd through the Southeast
US Thu night, then get wrapped up into the low over the ARKLATEX
Fri. It is yet to be determined if the Block will be strong enough
to keep PTC9 with the low or whether it will shear out over the nrn
mid-Atlantic Fri night. There is still some uncertainty with the
expected track of PTC9 as it moves nwd through the Southeast US and
where it goes thereafter. Latest operational model guidance suggests
the center may stay west of central NC (NC mtns), putting central NC
in the NE quadrant of the system on Fri. Heavy rainfall/flooding,
strong, gusty winds, and tornadoes will all be possible from Thu
night through Fri night. Latest rainfall forecast from the WPC has 2-
2.5 inches along the Yadkin River to half an inch/inch in the east.
With the overcast, rainy conditions Thu and Fri, highs should be
near to slightly above normal, mid/upper 70s to low/mid 80s, while
lows will be well above normal, in the mid/upper 60s to low 70s.
Saturday onward: The mid/upper level pattern may become more of an
Omega block than a Rex block over the weekend as the low to the
northeast shifts sewd over the nrn Atlantic, pushing the high/sub-
tropical ridge wwd, while the other low sits over the ARKLATEX
region. At the surface, as the remnants of PTC9 tries to continue
nwd along the Appalachians Fri night/Sat, high pressure over
southeast Canada will shift swwd through the Northeast and mid-
Atlantic coasts and overtake the system by Sat night/Sun. The medium-
range guidance diverges quite a bit over the weekend and it is
unclear whether high pressure will dominate or whether a low will
lift through and along the Southeast US coast late Sun/Mon. If, when
and how much precipitation there will be will depend on how that all
plays out, so will hold off on those specifics for now. As for
temperatures, generally expect temperatures to gradually decrease
from Sat to Mon.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 720 PM Monday...
IFR-MVFR ceilings are likely to redevelop in a persistently moist
regime in place overnight-Tue morning. The low overcast should then
slowly lift with diurnal heating once again during the late morning
through afternoon Tue. Additionally, there will be a chance of
showers, mainly west and south overnight. There will be a good
chance of showers/thunderstorms with diurnal heating on Tue, as a
series of disturbances aloft overspread and interact with a frontal
zone that will waver over the region.
Outlook: A persistently, unseasonably moist air mass in place over
cntl NC will favor repeated overnight-early day low ceilings and
visibility restrictions and also an above average chance of showers
and storms this week. The chance of both may be exacerbated by the
influence of Potential Tropical Cyclone Nine Thu-Sat.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...MWS
NEAR TERM...Swiggett/MWS
SHORT TERM...Kren
LONG TERM...KC
AVIATION...Badgett/MWS
Area Forecast Discussion
National Weather Service Springfield MO
600 PM CDT Mon Sep 23 2024
.KEY MESSAGES...
- Marginal (1 of 5) Risk for severe thunderstorms this afternoon
and evening across the eastern Ozarks. Potential hazards will
be damaging wind gusts up to 60 mph, large hail up to the size
of quarters. There is a very low chance of a tornado east of a
Gainesville to Salem line.
- Rainfall is likely this afternoon through this evening (60-90%
chance). Most locations will see an additional 0.10 to 0.50
inch of rainfall through tonight, with localized amounts of 1
to 2 inches east of Springfield.
- Much cooler temperatures will occur this week with highs in
the 70s.
- Rainfall chances (50-80%) continue to increase for late in
the week as confidence increases on track of the next system.
There is the potential for widespread and prolonged rainfall
with this system by Friday and Saturday.
&&
.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 218 PM CDT Mon Sep 23 2024
Current Conditions and Synoptic Pattern: Water vapor and upper
air analysis continues to show a slow moving shortwave across
Iowa into Kansas. Surface low pressure was located near West
Plains with a trailing front. An area of showers has developed
across southwest Missouri behind the main front in an area of
increased lift as the upper level jet noses into the area.
Clouds have kept temps down into the 60s to lower 70s with the
exception of south central Missouri where temps have increased
into the upper 70s. This is also where a pocket of 1000j/kg of
ML CAPE exists. We are currently in a lull of bulk shear
however a mid level speed max was moving up the Red River and
will likely increase bulk shear to 40kts by later this
afternoon.
This afternoon and evening: Lift will continue to increase and
expect a gradual uptick in showers and thunderstorms, especially
along and east of Highway 65 this afternoon, lasting through
late evening. Areas along and east of a Branson to Salem line
are in a marginal severe risk as this area is overlapped with ML
CAPE around 1000j/kg and increasing shear. A few multicells and
perhaps even some low topped supercells look to form late this
afternoon and evening. Latest RAP sounding for Oregon county
around 4-6pm shows the potential for around 1500j/kg of ML CAPE<
35-40kts effective shear which would be enough for a few severe
storms with large hail up to the size of quarters (if the
supercell threat was higher then the expected hail size would
need to be increased) and damaging winds up to 60 mph. There is
a low tornado risk briefly as the low passes with southeast
winds however this window looks brief with surface winds quickly
becoming southwesterly. Hodographs mainly look long and
straight which could promote a few splitting cells. The window
for severe storms is mainly from 3pm-9pm.
PW values of 1.5-1.6in will continue to promote heavy rainfall
rates. Latest HREF data suggests pockets around 0.5inch with
localized areas seeing 1-2 inches east of Highway 65. This could
produce a localized flash flood threat this evening. Most of the
heavier rainfall will have ended by 9pm however scattered
showers will likely continue across the eastern Ozarks through
the overnight hours as the shortwave trough moves through.
Locations further west will likely have low clouds and patchy
fog. Low temperatures will likely reach the upper 50s west of
Springfield.
Tuesday: Additional shortwave energy looks to drop down into the
area during the day which will promote clouds and cool temps
with northerly winds. Seeing a signal in short term guidance
that drizzle or light rain showers will occur across areas
northeast of Springfield during the day. If confidence increases
in this scenario then precip chances will need to be increased
(even though amounts would be very light). High temps in the 70s
are likely with the coolest readings (perhaps upper 60s), across
the northeast CWA.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 218 PM CDT Mon Sep 23 2024
An unsettled stretch is shaping up during the late week into the
weekend as an upper low drops south into Missouri and
potentially interacts with the developing Potential Tropical
Cyclone Nine. Guidance has come into decent agreement that the
upper low will move south over Missouri on Wednesday. There is a
10-20% chance of rain east of Springfield during the afternoon
however not expecting widespread rain.
The track of the tropical system will be key from Thursday into
the weekend as ensembles still continue to struggle with its
exact track through the southeast US. Ensemble clusters all
support rain across the area Thursday and Friday, especially
given the lift from the upper low and increasing moisture. It
should be noted that the multi modal mean in the ensemble
clusters shows the potential for over 2 inches of rainfall.
ECMWF extreme forecast index/shift of tails also shows the
potential for an anomalous rainfall event across the eastern
half of the area. Lastly, the latest NBM is showing greater than
a 60 percent chance of at least 3 inches of rainfall Thursday
through Saturday. With all this said, confidence is increasing
that a period of prolonged excessive rainfall is increasing
somewhere across the region, with increasing signals for the
eastern half of the area being in this zone. This will all be
dependent on the track of the tropical system and its
interaction with the upper low therefore stay up on the forecast
through the week. Temperatures will likely remain below average
through the week and into next week with precip and north
winds.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 600 PM CDT Mon Sep 23 2024
A system and associated frontal passage continue to bring
scattered showers and a few thunderstorms to the area. This
activity will slowly dissipate through the late evening from
west to east. Periods of MVFR to IFR flight conditions can be
expected with this activity, as result of reduced visibilities
and ceilings.
As the precipitation clears east of the terminals, some
guidance suggests areas of fog may build into the area. This may
result in reduced visibilities of 2 to 4 miles at times, though
the extent of dense fog remains uncertain towards sunrise
Tuesday morning. Nonetheless, IFR ceilings persist for most of
the area into Tuesday morning before improving to MVFR/VFR by
late Tuesday morning into the early afternoon. Winds are
forecast to be west to northwest at 5 to 10 knots through the
period.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
KS...None.
MO...None.
&&
$$
SHORT TERM...Burchfield
LONG TERM...Burchfield
AVIATION...Perez