Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/19/24
Area Forecast Discussion
National Weather Service Fort Worth TX
710 PM CDT Thu Apr 18 2024
...New Short Term, Aviation...
.SHORT TERM... /NEW/
/This Evening through Saturday Morning/
The cold front is currently located near a Bonham-Cleburne-Llano
line and will steadily continue south/southeast over the course
of this evening. Some convective development has been observed
over the last couple hours, mainly across western Central Texas
where large hail has been reported. The potential for scattered
showers and storms along the front will continue through this
evening as RAP analysis shows the front moving into an unstable
airmass with 2000-3000 J/kg MLCAPE and 7-8 degC/km lapse rates.
This parameter space will continue to promote strong to severe
storms capable of hail and damaging winds. There continues to be a
non-zero tornado threat with this activity, but low-level SRH is
generally unfavorable enough to keep this threat on the lower
side. The front will continue to move through the region,
eventually exiting completely near daybreak Friday.
The cold front will eventually stall across South Texas, leaving
our area fully entrenched within the cooler post-frontal airmass.
Cloud cover will stick around as mid- and low-level moisture will
not be completely scoured out behind the boundary. The afternoon
hours should remain relatively dry as a lack of lift should keep
most precipitation from forming until the late evening and
overnight hours. By this time, an upper level shortwave will move
into the Central Plains and spread increased forcing for ascent
overtop the cooler post-frontal airmass. Expect more widespread
showers and storms to blossom across North and Central Texas
during the early morning hours on Saturday. Sounding profiles show
steep lapse rates and enough deep layer shear/MUCAPE to promote
some stronger storms capable of small hail, but the overall severe
threat is low at this time. Instances of heavy rain are also
expected through Saturday morning as PWATs in excess of 1.5" will
be widespread across North and Central Texas.
Prater
&&
.LONG TERM... /Issued 224 PM CDT Thu Apr 18 2024/
/Friday Night Through Next Thursday/
...Scattered to numerous showers and storms expected Saturday
with the potential for localized heavy rainfall and flooding
concerns...
Large scale forcing will increase across the Southern Plains this
weekend as a mid-level shortwave trough approaches from the
southwest. Height falls will start overspreading the state Friday
night, inducing stronger warm and moist advection overtop the cool
near-surface airmass left behind by today`s cold front. The
ascending air should first yield thickening cloud cover with a
broad area of showers and thunderstorms developing overnight in
response to the strengthening low level jet.
NAM forecast soundings show the boundary layer will be strongly
capped making surface-based convection unlikely Friday evening.
Moderately strong elevated instability amid the ongoing isentropic
ascent should still lead to a rapid increase in the coverage of
showers and thunderstorms after midnight Saturday. The severe hail
threat will be inhibited by the tall, skinny CAPE profiles
(weaker parcel accelerations) in the forecast soundings. However,
steep mid-level lapse rates and adequate deep layer shear should
still support some instances of at least small hail Friday night
into Saturday morning.
The shortwave trough will eject across the region on Saturday as
the front continues to slowly push towards the coast. Scattered to
numerous showers with embedded thunderstorms are expected to
develop across the region with the area of greatest coverage
shifting from North Texas and the Big Country (Saturday morning
and afternoon) to Central and East Texas (Saturday evening/night).
Though a few strong storms cannot be completely ruled out,
widespread cloud cover and rain should limit heating/instability
and the overall potential for severe weather. The main concern on
Saturday will be localized heavy rainfall, especially in areas
where the soils are still saturated from heavy rainfall over the
past few weeks. Additionally, training storms and heavier
convective rain rates may lead to flood issues including minor
river flooding. Generally, 1-2.5 inches is expected though
isolated higher amounts are possible. The higher totals are
concentrated mostly near and east of the I-35 corridor.
In the wake of the departing shortwave, rain chances will end
Sunday morning from west to east as subsidence increases over the
region. After a weekend of well-below normal temperatures (highs
in the 60s, lows in the 40s/50s), temperature recovery will begin
early next week as the surface high shifts east and south winds
return amid mostly clear skies. Dry conditions should prevail
through mid-week before a potential Alberta Clipper positions
North and Central Texas beneath northwest flow ahead of a
developing western CONUS upper trough. As expected, there is
little model agreement beyond Day 7 (Wednesday) so this portions
of the forecast is likely to change over the weekend.
12
&&
.AVIATION... /NEW/
/00Z TAFs/
The cold front is currently between D10 and ACT, and will move
south through the rest of tonight. Isolated showers and storms
will continue to be possible along the front, with best impact
timing at ACT between 02-04Z this evening. Behind the front,
expect breezy northerly winds through the early morning. A blanket
of MVFR stratus will build northward across the region overnight
into tomorrow morning, though the exact northern extent is
uncertain at this time. Have continued the MVFR as a TEMPO from
13-17Z in D10 to account for the lowered probabilities and the
continued uncertainty. The stratus deck should scatter out by
early-mid afternoon tomorrow, with VFR prevailing once again.
Another round of stratus is expected just after the 30 hour mark,
and will be included in future TAFs.
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 56 71 58 65 50 / 20 5 80 90 90
Waco 59 74 62 70 51 / 40 5 50 80 100
Paris 54 69 53 59 48 / 40 20 80 90 80
Denton 52 69 54 62 47 / 10 5 80 90 90
McKinney 54 69 55 63 48 / 20 10 80 90 90
Dallas 57 72 58 64 51 / 20 5 80 90 90
Terrell 56 71 57 65 49 / 40 10 70 90 100
Corsicana 60 74 61 70 51 / 40 10 50 80 100
Temple 61 75 63 73 51 / 20 10 40 80 100
Mineral Wells 53 70 56 64 47 / 10 5 80 90 90
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Grand Rapids MI
832 PM EDT Thu Apr 18 2024
.KEY MESSAGES...
- Rain tonight, and slight chance lightning in southern Mich.
- Cooler Friday night, near freezing
- Multiple chances of frost/freeze next week
- Only chance of rain Monday night-Tuesday
&&
.DISCUSSION...
Issued at 340 PM EDT Thu Apr 18 2024
- Rain tonight, and slight chance lightning in southern Mich.
Virga and areas of light rain this afternoon will give way to a
period of rain overnight as a wave of low pressure along a cold
front tracks into the southern Great Lakes region. HREF and NBM QPF
indicate a good potential for at least 0.25 inches of rainfall, with
a narrower stripe of 0.50 to 0.75 inches possible from southwest
Michigan to the Saginaw valley. The HRRR and NAM-Nest soundings
around I-94 this evening have MUCAPE greater than 100 J/kg
originating from moist parcels at 800-750 mb underneath fairly steep
lapse rates that extend up to 500 mb (-20 C). So this elevated
convection in southern Michigan could produce a few lightning
flashes and rumbles of thunder, with the threat ramping up after
sunset.
- Cooler Friday night, near freezing
With increasing vulnerability to temperatures below 32 degrees among
blossoming vegetation, Friday night will kick off about a weeklong
pattern with threats of frost/freeze conditions (not every night of
the next seven, but several of them). Temperatures are expected to
drop into the mid 30s Friday night as progressively colder air is
transported into the area among westerly winds. However, a pressure
gradient will still exist given the center of high pressure being
back in the northern Plains, so this may keep the surface winds up
enough to prevent a sharper temperature inversion from becoming
established near ground level.
- Multiple chances of frost/freeze next week
One concern that is growing for the colder spell this weekend, and
cooler temperatures behind the Tuesday system are some frost/freeze
possibilities. Recent coordination with agricultural interests
including Michigan State extension, reveals that fruit trees are
entering a vulnerable period in their growth for most of the area,
except along the U.S.-10 corridor. The beginning of the growing
season has been coordinated with surrounding offices.
We are looking at multiple nights where temperatures will drop to
and a little below freezing. The nights with these concerns include
Saturday and Sunday nights, and Tuesday and Wednesday nights. We are
way too far out in time right now to fine tune details. This will be
something we will continue to monitor and issue headlines for if
needed as we come up to those conditions.
- Only chance of rain Monday night-Tuesday
The weather is looking very quiet for the area from this weekend
through next Thursday. The only caveat to this will be a system that
is forecast to move through the area from late Monday into Tuesday.
Behind the system that moves through on Friday, the area will be
under the influence of NW flow aloft downstream of the upper ridge
expected to be parked for a few days over the Plains. We will be
under increasing subsidence, with a cool flow from the North and
Northwest into early next week. This period should be rather dry
also, with a good deal of sunshine during the days. This may start
to create some Fire Weather concerns by later in the weekend after a
couple of dry days.
The one system that looks to affect the area after Friday`s system
will be a short wave that moves through late Monday through Tuesday.
This energy will have its origins from the upper low off of the
Western U.S. coast. It will tamp down the weak ridge over the
Plains, and move through the area. Right now, it does look like it
will have a sufficient low level feed of moisture from the Gulf to
provide good rain chances for the area at that time. I would expect
the rain amounts to end up a little less than advertised at the
moment with a lot of dry air that is expected to have to be
overcome.
Once the system on Tuesday moves out, we will see the upper ridge
over the Plains become re-established as a large upper low complex
moves in over the western portion of the CONUS. This will set us
back up with drier conditions as heights build for the rest of the
week.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 830 PM EDT Thu Apr 18 2024
Rain showers have begun and will continue overnight into tomorrow.
There will be a period of MVFR then dropping to IFR cigs and
vsbys beginning around 01Z. Best chances of IFR will be between
03Z to 11Z before rain tapers off.
Some low clouds will linger after the rain ends, and then
clearing should take place toward or just after daybreak Friday.
Winds will become a bit gusty from the NW Friday morning, with
gusts up to 30 knots expected.
&&
.MARINE...
Issued at 340 PM EDT Thu Apr 18 2024
Hazardous waves for small craft will likely build up between South
Haven and Whitehall early Friday morning and expand farther north
and south for at least a portion of the day. Will extend the small
craft advisory northward to Manistee and take it into Friday evening
based on latest model guidance. There may be a slight lull in the
conditions Friday night, mainly near South Haven, but the small
craft advisory may also need to be extended through the day
Saturday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 6 AM to 8 PM EDT Friday for LMZ844>849.
&&
$$
DISCUSSION...NJJ/CAS
AVIATION...Ceru/NJJ
MARINE...CAS
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
949 PM EDT Thu Apr 18 2024
.SYNOPSIS...
Showers and thunderstorms are possible Friday as a cold front
crosses the area, but unseasonably warm weather continues through
Saturday. Below-normal temperatures and widespread light rain is
expected Sunday with cool but drier weather on Monday. Drier and
warmer weather will return to the area Tuesday through Thursday
of next week.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 935 PM Thursday: A series of short wave troughs will push a
cold front across the TN and OH Valleys overnight. Guidance agrees
that mid/high clouds will continue to steadily thicken, with lower
clouds increasing toward daybreak. The 00Z run of the HRRR has
backed off considerably on the potential for pre-sunrise/pre-frontal
convection impacting the CWA...with more of a focus on late morning
(and keeping it confined to the mountains at that.) PoPs have
therefore been lowered across western areas, with likelies confined
to a sliver along the TN/NC border. A strong storm or two can`t be
ruled out across the far west toward sunrise, but a combination of
modest nocturnal instability and unimpressive shear parameters
should preclude a severe storm threat. QPF doesn`t look especially
heavy either, although some moderate amounts are possible. Min temps
will be around 10 degrees above normal.
Convection is expected to reignites during the afternoon as the cold
front itself moves in from the west. Indeed, the trend toward less
coverage of morning convection suggests better potential for
redevelopment during the afternoon. Best coverage will be over NC
and the central and eastern Upstate, with isolated coverage over the
Upper Savannah River valley. An isolated severe storm or two will be
possible with moderate CAPE and shear developing. Right now, it
doesn`t look to be especially organized even with the front moving
in. Again, some moderate QPF is possible but significant coverage of
heavy rainfall is unlikely. Highs will be a little tricky given the
clouds and potentially two rounds of convection. For now, have highs
around 10 degrees above normal.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 200 PM EDT Thursday: A cold front will be draped across the
center of the forecast area early Friday evening before gradually
pushing south and east Friday night into daybreak morning. CAMs show
the potential for lingering isolated convection through late Friday
evening, so have chance PoPs in place through late Friday night
across the western and eastern zones. The SPC Day 2 Severe Wx
Outlook has the western Carolinas in Marginal Risk for isolated
strong to severe storms, thus a few strong to severe storms will be
possible through the evening hours. The main potential impacts with
any storm that manages to become severe will be large hail and
damaging wind gusts. Lows Friday night will end up around 12-15
degrees above climo thanks to increasing cloud cover and convection.
The cold front will be located just south of the forecast area on
Saturday, which may allow additional isolated convection to develop
during the afternoon and evening hours. Have chance PoPs in place
again on Saturday to account for this potential, but the NAMnest
shows mostly dry conditions. Thus, confidence on PoPs for Saturday
is low. The severe weather threat looks to be lower on Saturday, but
we cannot not rule out an isolated strong storm or two if convection
manages to develop. Despite cloud cover lingering on Saturday, highs
will be around 4-8 degrees above climo across most locations.
However, the NC/TN border will likely see highs a few to several
degrees below climo behind the cold front.
The front will stall across the Gulf Coast Saturday night into
Sunday while sfc high pressure gradually builds into the central
CONUS leading to much cooler temperatures. Meanwhile, upper
shortwaves will track across the Southeast Saturday night into
Sunday leading to gradually increasing rain chances. Could not rule
out some isolated thunderstorms Saturday evening thanks to lingering
instability. However, thunder is not expected on Sunday thanks to in-
situ CAD leading to a more stable airmass. Have chance PoPs Saturday
night with likely to categorical PoPs on Sunday. Lows Saturday night
will end up around 4-7 degrees above climo, with highs on Sunday
ending up around 10-13 degrees below climo.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 230 PM EDT Thursday: Rain chances will linger through Sunday
evening before gradually tapering off overnight as the upper
shortwaves push east of the western Carolinas. Thus, have chance
PoPs in place through late Sunday night across the forecast area.
Lows Sunday night will end up near climo to a few degrees below
climo despite lingering cloud cover. The aforementioned sfc high in
the short term will gradually push into the eastern CONUS Monday
into Tuesday leading to drier conditions. CAD looks to linger
through Monday before gradually dissipating Monday night into early
Tuesday. This will lead to another round of below climo temps, ~7-11
degrees, Monday afternoon. Highs on Tuesday will be noticeably
warmer thanks to the sfc high being directly overhead the Carolinas
and leading to S/SSW`ly flow. Lows Monday night will end up a few
degrees below climo thanks to mostly clear skies. Lows Tuesday night
will end up a few degrees above climo ahead of an approaching cold
front. A cold front looks to track across the western Carolinas
overnight Tuesday into Wednesday, mainly leading to increased cloud
cover, especially along the western North Carolina mountains. Rain
chances also look to return with this front, but should remain
confined to the western North Carolina mountains. Thus, capped PoPs
to slight chance for now across these zones. Both highs and lows on
Wednesday will end up a few degrees above climo. Dry high pressure
will build back into the region behind the departing front Wednesday
night into Thursday leading to drier conditions and slightly cooler
temps.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: VFR conditions are expected to predominate
through this TAF period. Chances for showers and perhaps some TS
will increase ahead of a cold front toward daybreak Friday,
especially across western areas. Prob30s are included at all sites
except KCLT during the morning. While -SHRA is advertised at most
sites, -TSRA is included in the Prob30 at KAND. Convection is
expected to push east of the Terminal Forecast Area during the late
morning/early afternoon. However, conditions may become favorable
for redevelopment of scattered activity later in the afternoon, and
most sites get a second Prob30 for -TSRA during the afternoon. Winds
will generally be light/vrbl overnight...perhaps favoring a light
S/SW component at some sites. Winds will then increase from the SW
at 5-10 kts during the daylight hours Friday.
Outlook: As a cold front sags south across the area, another round
of convection is possible Saturday, mainly during the afternoon.
Rain and possibly isolated thunderstorms are expected to develop
north of the front on Sunday, likely resulting in restrictions for
at least the southern part of the area. Drier conditions return
Monday, continuing into Tuesday.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...DEO
NEAR TERM...JDL/RWH
SHORT TERM...AR
LONG TERM...AR
AVIATION...JDL
Area Forecast Discussion
National Weather Service Indianapolis IN
924 PM EDT Thu Apr 18 2024
.KEY MESSAGES...
- Severe storms and are possible through the early overnight and
locally heavy rain is possible through daybreak.
- Cooler but dry Friday through Monday. Some frost potential mainly
north Sunday morning, more widespread frost possible Monday
morning.
- Increasing rain chances next Tuesday, low chance for thunderstorms
&&
.FORECAST UPDATE...
Issued at 923 PM EDT Thu Apr 18 2024
Latest radar loop was showing a broken line of strong to severe
thunderstorms moving east and southeast across east central Illinois
with individual cells moving northeast around 30 mph. These storms
were within a SW-NE oriented instability axis with SB CAPE to 1500+
J/kg. Further west, CAPEs were only around 500 J/kg, over the lower
Wabash Valley, where the Severe Thunderstorm Watch extended to. HRRR
has had a good handle on this broken line of convection and moves it
over central Indiana 02z-06z. The combination of low level
convergence from frontal boundaries and a surface low tracking
through, moisture transport, instability and 30 to 40 knot deep
shear has lead to some upstream damage over the LSX, ILX and PAH
forecast areas.
CAMS in good agreement the squall line will gradually weaken as it
moves into the more stable air in place across east central and
southeastern parts of central Indiana. That said, the Watch
currently runs through 3 AM over parts of the lower Wabash Valley.
Radar was showing additional convection further northwest across
west central Illinois. This convection should roll across central
Indiana overnight with instability waning, not be a course for
concern regarding severe weather.
Upstream 6 hour MRMS QPE was showing a few localized areas of an
inch or so to 2 inches or so, but otherwise, don`t atnicipate to
many water concerns in addition to the ongoing river flooding.
Wind gusts will approach 25 mph and turn to the northwest overnight
in the wake of the cold front. The gusty winds and cloud cover will
temper the cold advection and should keep temperatures to no lower
than middle 40s to lower 50s by daybreak.
&&
.SHORT TERM (This evening through Friday)...
Issued at 317 PM EDT Thu Apr 18 2024
It`s another day of above normal temperatures and a conditional
threat for severe weather. Satellite shows high clouds currently
over central Indiana while surface observations show temperatures
warming into the 70s and dew points creeping higher over the SW
counties.
Thunderstorms will move in this evening, likely entering the state
between 8 and 10 pm and tracking eastward through the overnight
hours. The storms in question are currently over Missouri as of this
afternoon. As they approach, winds will start to increase to
around 10-15 mph with non-thunderstorm gusts possible through the
night. Withe the severe threat, confidence remains low given the
conditional nature. The latest CAMs show that variables may not
line up quite right, but if they do damaging winds will be the
main threat while an isolated tornado and isolated hail can`t be
ruled out. Isolated flooding may also be a concern as up to an
inch of rain will be possible as the line of storms moves through
a region that already has a pretty saturated ground.
The best threat for severe weather will be over the SW counties
where the best instability and moisture content will be. As the
storms reach the area, CAPE of 500 to 1000 J/kg are expected,
especially over those SW counties, but looks to drop to less than
500 J/kg over the following few hours. However, latest CAMs are
showing less than impressive shear and helicity over the area and
the surface low driving this system looks to lift as it reaches
central Indiana. Lapse rates of 7 C/km may still be around when the
line arrives but confidence is low and it seems more likely that
those will have dropped off beforehand.
The line of storms and the cold front causing them are expected to
move out of the forecast area by sunrise or shortly after. Highs
tomorrow will be lower and closer to normal, reaching only the mid
50s to low 60s. Otherwise, nice weather is expected for the day
tomorrow with only partly cloudy skies remaining.
&&
.LONG TERM (Friday night through Thursday)...
Issued at 317 PM EDT Thu Apr 18 2024
Friday night through Monday...
Quiet weather conditions are expected for several days as surface
high pressure remains dominant over the region. Aloft, guidance
shows a few upper level impulses traversing the region which could
help to keep clouds around at times over the weekend. A weak LLJ
associated with an upper disturbance moving through Saturday will
likely help promote breezy conditions. Gusts up to 25 mph are
possible during the day.
Expect temperatures to trend cooler heading into the weekend due to
cold air advection. Lows dropping into the 30s both Saturday/Sunday
night combined with relatively light winds could support the
potential for frost. There is higher confidence in frost Sunday
night into Monday morning at this time since guidance shows much
less cloud cover. Greater cloud cover from an upper level impulse
Saturday night leads to higher uncertainty. Highs are generally
going to range from the low 50s to near 60F over the weekend before
warming up early next week.
Monday night onward...
Rain chances return late Monday night into Tuesday as a shortwave
trough and associated low pressure system move across the Great
Lakes Region. Return flow ahead of the approaching system should
allow for temperatures to continue moderating. Sufficient moisture
return combined with increasing dynamics supports likely POPs on
Tuesday. The system is likely going to move out Tuesday night. Cold
air advection and surface high pressure building in behind the
departing low will allow for quiet weather conditions to return
briefly before another system approaches late next week.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 616 PM EDT Thu Apr 18 2024
Impacts:
- Showers and thunderstorms moving in 00Z-02Z and ending 09z-11z
- MVFR and briefly worse flying conditions will accompany the
convection and MVFR or worse will likely hang around a few
hours after the convection moves out
- Damaging winds to 50 knots possible in the stronger cells
- Winds will shift to NW, in the wake of the front, with gusts to
near 25 knots, after 05z-15z
Discussion:
Showers and thunderstorms, with the leading edge likely linear, will
sweep across central Indiana late this evening into the overnight.
Deteriorating flying conditions will accompany the convection and
low ceilings will hang around a few hours after frontal passage.
Damaging winds are possible mainly with the leading line and later
winds will turn northwest and gust to near 25 knots behind the cold
front.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...MK
SHORT TERM...KF
LONG TERM...Melo
AVIATION...MK
Area Forecast Discussion
National Weather Service Louisville KY
1115 PM EDT Thu Apr 18 2024
.KEY MESSAGES...
* Strong to severe storms possible Thursday night. Highest risk of
severe storms will be generally west of I-65.
* Much cooler weather this weekend. Next chance of rain arrives in
the Tuesday/Wednesday timeframe.
&&
.UPDATE...
Issued at 1114 PM EDT Thu Apr 18 2024
The northern edge of Severe Thunderstorm Watch #129 has been
spatially extended to the east a row or two of counties to account
for a section of the ongoing broken convective line that might
continue moving into an environment still marginally conducive for
damaging winds, as highlighted by the latest SDF ACARS. In addition,
watching for storm mergers and boundary collisions that could help
mix down momentum aloft. Overall, ML-based HRRR model guidance still
hints at a decreasing severe threat for the coming hours as the line
progresses to the east.
&&
.MESOSCALE...
Issued at 947 PM EDT Thu Apr 18 2024
A few discrete warms sector cells have been firing off ahead of the
main convective line, which has been expected and picked up well in
the earlier CAM runs. It appears these cells are popping up in an
area of localized theta-e advection and deep moisture convergence
axis, and underneath a pocket of positive vorticity advection. SPC
Mesoanalysis suggest these storms are firing along a gradient of
SBCAPE, but have struggled to become severe. Will keep an eye on
these.
Severe thunderstorm line is charging across eastern Illinois at this
hour, and is noticeably accelerating as the cold pool pushes it
further east. At this pace, believe the line will be arriving into
Dubois County by 0230z. ACARS sounding out of SDF does show some
SBCAPE lingering, but thinking MLCIN will help weaken the line as it
approaches the I-65 corridor by 04-05z. HRRR 00z data supports this
too, with low level stable layer expected to help weaken this
convective line in a few hours. Will need to keep tabs on additional
convection across south-central KY later tonight though, where there
is potential to remain unstable within the warm sector prior to the
cold front arrival.
&&
.SHORT TERM /THROUGH FRIDAY/...
Issued at 346 PM EDT Thu Apr 18 2024
Currently, satellite imagery is showing a warm front stretching to
the northwest through southern Indiana and central Kentucky. This
front arches to the west into a surface low in western Missouri. To
the north of this front, dew points are in the 40s and 50s. To the
south of the front, mid 60s, and as we head through the afternoon
and evening hours, the surface low, part of a larger cold front
extending to the north and south, will begin moving towards
Indianapolis. This will cause the warm front and cold front to
develop an inverted "V" look by 0z over southern Illinois, eastern
Missouri and western Kentucky. Dew points over southern Indiana and
central Kentucky will likely drop into the 50s as the region becomes
better mixed.
As 1-2z approaches, the surface low will be moving from Illinois
into central Indiana. The area under the aforementioned inverted "V"
will see dew points in the mid 60s. Again, this is the area in
between the warm and cold fronts. On the leading edge, the warm
front will likely kick off convection over western Kentucky and
southward while the cold front running through Chicago arches
southward through southern Illinois. As these two lines continue
eastwards. The front line could become the dominate line for
southern part of the cold front over Missouri and could combine with
the northern half of the cold front, or it could remain as two
separate lines and join with the cold front over southern Indiana.
It doesn`t make much of a difference, except some over central
Kentucky could get one or two lines of convection.
The timing is going to help us from a severe weather standpoint.
Since the fronts won`t move through until after sunset, an inversion
is expected to develop and make any convection elevated. This will
limit potential wind energy from reaching the ground. Overall shear
is fairly weak. Think the current SPC outlook is a little bullish
over our CWA.
Winds tonight will remain out of the south to southwest around 5-10
mph. A few gusts around 30 mph will be possible as the line of
convection passes, and as the cold front begins to move through
during the morning on Friday, winds will quickly veer towards the
north-northwest increasing cold air advection into the area. Winds
tomorrow will stay around 10 mph as they gust to 15-20 mph.
WAA will keep temperatures warm tonight, only dropping into the 50s
to low 60s. Tomorrow, the sun is expected to return, but CAA will
limit temperatures to the 60s. A few in the Lake Cumberland region
could hit the low 70s.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 346 PM EDT Thu Apr 18 2024
Friday Night through Monday Night..
Dry conditions are expected Friday night and into Saturday as a
surface high pressure system builds into the region with a dry zonal
flow pattern aloft. A southern stream system may graze the far
southern part of KY Saturday night and Sunday morning, but the
latest trends in the data suggests a drier forecast may end up
prevailing. Lows Friday night will dip into the upper 30s and lower
40s. Highs Saturday will be cool highs in the 60-65 degree range.
Lows Saturday night should be a bit cooler with lows in the upper
30s across much of the region. Areas south of the Cumberland
Parkway may only drop into the lower 40s. Continued cool conditions
are expected for Sunday with highs in the upper 50s to near 60.
Depending on cloud cover conditions Sunday night, we could see some
patchy frost in southern IN and the KY Bluegrass region as lows dip
into the mid 30s. Monday will see warmer conditions returning to
the area with temps warming up into the mid-upper 60s.
Tuesday through Thursday...
Forecast confidence continues to increase in another chance of
showers and storms coming into the region in the late Tuesday/early
Wednesday time frame as a shortwave trough aloft moves through the
region. The previous forecast of solid PoP coverage still looks
good here. Temperatures through the period will warm into the upper
60s to the lower 70s with overnight lows in the low-mid 40s.
&&
.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 744 PM EDT Thu Apr 18 2024
VFR conditions will deteriorate this evening as showers and
thunderstorms approach the region ahead of a cold front. Expect
impacts to ceilings and vis as thunderstorms roll through from west
to east, first at HNB in the next few hours, and later tonight at
LEX and RGA. The peak for convective activity will be from 02-09z
tonight. After the storms pass, ceilings will lower to MVFR and
likely below the 2k ft fuel alternate threshold near the pre-dawn
hours. There appears to be a short window where ceilings could drop
to IFR, so included a TEMPO group at all terminals for that as well.
We`ll gradually improve to VFR conditions again by late tomorrow
morning or early afternoon, with post-frontal winds from the north.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
MESOSCALE...CJP
UPDATE...ALL
SHORT TERM...KDW
LONG TERM...MJ
AVIATION...CJP
Area Forecast Discussion
National Weather Service Memphis TN
952 PM CDT Thu Apr 18 2024
...New UPDATE...
.UPDATE...
Issued at 952 PM CDT Thu Apr 18 2024
The first batch of showers and thunderstorms has moved off to the
east but round 2 is approaching the Mid-South along a cold front
stretching from central IL into northern AR. A fair amount of
instability is still present across the region with MUCAPE still
on the order of 1000-2000 J/kg. Surface-based instability appears
to be largely capped at the moment. Deep-layer shear has increased
over the past few hours with effective bulk wind shear now in the
40-45 kt range along and west of the MS River.
The increasing low-level jet has also carved out a looping
hodograph which has enhanced storm-relative helicity across the
area. The NQA VAD hodograph indicates 0-1 km SRH of 440 m2/s2
which is significantly more than the RAP13 has been alluding to.
This could lead to some embedded supercell structures within the
approaching line. Fortunately, the 0-3 km bulk wind shear is
limited to 25-30 kts from the west-northwest. This would provide
only marginally sufficient wind shear to support mesovortex
formation along the line which should limit the potential for
tornadoes. Damaging wind and large hail look to the be the
primary threat should this convection remain rooted in the
boundary layer.
MJ
&&
.MESOSCALE UPDATE FOR SEVERE WEATHER...
Issued at 533 PM CDT Thu Apr 18 2024
We`re finally beginning to see more robust storm development north
of Interstate 40. This is where the greatest instability is
located. Farther south, the cap is stronger and showers/storms are
really struggling to maintain/gain intensity despite an
approaching shortwave trough near the Arklamiss. The latest
analysis indicates MLCAPE (instability) on the order of 2000 J/kg
from near Memphis into southeast Missouri (with 0-3 km MLCAPE near
or above 100 J/kg). Mid-level lapse rates are fairly steep across
portions of AR/MO/TN by Mid-South standards (near 7 C/km) which
will support stronger mid-level updrafts and hail growth. One of
the negatives is the lack of stronger deep-layer shear. Bulk shear
isn`t all that bad at 35 kts or so, but that is more marginal for
supercell development, especially with 0-3 km SRH at or below 100
m2/s2. This suggests more in the way of multicells with weak
supercell characteristics in general. Large hail and localized
damaging wind are the primary concerns. Weak low-level wind shear
will keep the tornado threat low for now.
Storms upstream are expected to grow upscale into a linear mode,
moving into the Mid-South later this evening. The greatest
uncertainty will be whether or not the air mass preceding this
line of storms is able to remain surface-based instability. If so,
damaging winds will be a larger concern. If not, storms may remain
elevated which will limit the severe weather potential.
MJ
&&
.SYNOPSIS...
Issued at 333 PM CDT Thu Apr 18 2024
Scattered showers and thunderstorms will continue over the
Midsouth tonight, in advance of an upper level trough lifting
through the mid-Mississippi River Valley. Severe thunderstorms
will be possible, especially north of a Jonesboro Arkansas to
Jackson Tennessee line. Damaging winds and large hail will be the
primary threats. A few short-lived tornadoes will also be possible
through the early overnight hours, mainly to north and west of the
Memphis metro area.
Additional showers are expected across the Midsouth through early
Sunday, with isolated thunderstorms over north Mississippi. Severe
thunderstorm chances will be low. A reinforcing cold front will
push through the Midsouth Saturday night and early Sunday,
bringing low humidity and cool conditions for Sunday night through
early Tuesday.
&&
.DISCUSSION...
(This evening through next Wednesday)
Issued at 333 PM CDT Thu Apr 18 2024
Primary forecast concern remains severe thunderstorm chances
through tonight. SPC/RAP mesoanalysis showed mixed-layer CAPE of
1500-2000 J/kg along and west of the MS River. Mixed layer CINH
was estimated at zero across the Midsouth, but early afternoon
convective trends suggest consequential CINH remains. 12Z
soundings from LZK, SGF and JAN showed a stout elevated mixed
layer (EML) and underlying inversion. 17Z aircraft sounding from
LIT showed this EML remained strong, and based at 750mb. GOES
visible imagery showed multiple standing wave clouds over
northwest AR, suggestive of an overlying capping inversion.
Immediately west, frontal convergence was evident over far
northeast OK and southwest MO, but deep convection was limited to
areas further north along the front, over central MO.
To our south, thunderstorms persisted through most of the morning
and early afternoon. This convection initiated on an elevated
boundary, near the base of a relatively low (900mb) EML. This
convection was not initialized on early morning runs of the HRRR,
despite a pronounced upstream shortwave evident on GOES water
vapor imagery. The Arklamiss/central MS storms persisted into
central MS at midafternoon and have spread considerable high
cloudiness over north MS. This has limited surface heating and
ability to sustain deep convection - at least to this point.
Should a storm or two manage to break through the low level
capping inversion, robust CAPE and steep midlevel lapse rates will
support large hail over any portion of the Midsouth. Any of three
following features may aid in the breaking the convective cap: height
falls associated with aforementioned shortwave exiting the Arklatex,
strong surface heating, and general height falls associated with
the longwave trough passage over the mid-MS River Valley. None of
these are a sure bet, hence the lower typical Day 1 confidence
level in severe storms.
Should severe storms fail to materialize this afternoon, it
doesn`t mean we`re out of the woods. NAM and HRRR depict a
pronounced strengthening of 925mb SSW winds late afternoon and
evening. This is likely a contributing factor the looping model-
derived hodographs over eastern AR late this evening. If storms
manage to become surface-based, a mid to late evening QLCS
tornado threat may be realized over eastern AR. After midnight,
severe threat should diminish with strengthening low level
inversion, weakening elevated instability and weakening/veering of
the low level jet.
Comparatively tranquil weather will prevail Friday and Saturday,
as a surface cold front stalls over north MS, parallel to the
upper level flow. An open southern branch trough will lift into TX
on Saturday, with downstream moisture bringing showers mainly
south of I-40. A few thunderstorms will be possible over north MS,
but similar to yesterday, NBM thunder probabilities appear too
high/too far north Friday night through Sunday morning.
A reinforcing cold frontal passage Sunday night will bring dry and
cool conditions, with temperatures Sunday and Monday more typical
of early March.
PWB
&&
.AVIATION...
(00Z TAFS)
Issued at 615 PM CDT Thu Apr 18 2024
Showers and thunderstorms along a pre-frontal trough will move
east of MKL/TUP over the next few hours. Another round of showers
and thunderstorms will be possible later this evening into early
Friday morning along a cold front. Latest probabilistic guidance
shows a high potential for post-frontal MVFR/IFR low stratus to
develop across the area overnight into Friday morning. Conditions
will gradually improve later Friday morning into Friday afternoon.
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
PUBLIC FORECAST...PWB
AVIATION...CJC
Area Forecast Discussion
National Weather Service Morristown TN
911 PM EDT Thu Apr 18 2024
...New UPDATE...
.UPDATE...
Issued at 906 PM EDT Thu Apr 18 2024
Will slow the forecast arrival of showers and storms tonight
based on latest radar and hi-res CAM trends. Otherwise the
forecast for tonight generally still looks to be on track, so the
only other changes will be minor tweaks to temps and dew points.
&&
.SHORT TERM...
(This evening through Friday)
Issued at 246 PM EDT Thu Apr 18 2024
1. Showers and thunderstorms expected overnight, stronger storms
more likely, but not a certainty, west of Knoxville.
2. A second chance for scattered strong thunderstorms exists Friday
afternoon across the Tennessee valley. Gusty winds and large hail
possible with the afternoon thunderstorms.
Discussion:
Cold front begins the period across Missouri and will march
eastwards with time until making it to Tennessee by the end of the
short term Friday evening. A couple rounds of showers and
thunderstorms will exist in the warm sector ahead of the front.
First round of showers and thunderstorms is expected overnight
tonight. This means that the remainder of the evening today is
expected to remain dry, so that`s good news. Guidance indicates
showers and storms tonight will generally ride the midlevel heights
axis as the ridge continues to move off to our east by Friday
morning. Given the time of the day being the most unfavorable for
thunderstorm intensity and the ability of storms to mix winds down
to the surface, not feeling aggressive with the idea of strong
storms overnight. Additionally, the more recent CAM runs have backed
off on storm cell intensity and organization for overnight. HRRR has
trended towards an even more scattered, unorganized, depiction for
overnight into morning storms. Still, a few rumbles of thunder are
possible given elevated CAPE as the remnants of the convection from
Western Kentucky and Middle Tennessee move into East Tennessee.
Convection should exit or dissipate by mid-morning, yielding a few
hour pause until the second round during the afternoon. An
approaching 500 mb speed max moves from west to east across
Tennessee heading into peak daytime heating, increasing flow aloft
from 30 knots to 50 knots. Some of the guidance (notably the HRRR
and high res NAM) depict a quick and robust recovery into Friday
afternoon, along with a favorable convective initiation in the
Tennessee valley to take advantage of their modeled environments.
Hodograph shapes are fairly linear, and given the increasing flow
providing plenty of effective shear, a risk for damaging winds and
severe hail is possible. One big uncertainty is cloud cover is
expected to be present in the morning through the afternoon storms,
so not certain how that hinders the convective environment. Still,
the environment will need to be watched for strong thunderstorms.
&&
.LONG TERM...
(Friday night through next Thursday)
Issued at 246 PM EDT Thu Apr 18 2024
Key Messages:
1. Outside of rain chances on Sunday, drier and cooler conditions
are expected into early next week, especially on Monday.
2. Rain chances and more seasonal temperatures will return by
Wednesday and Thursday.
Friday Night through Monday
At the start of the period, subtle troughing will be in place across
the eastern U.S. with a strong upper jet to our north. A cold front
will be moving through the area ahead of high pressure expanding
from the northwest. During this time, lingering showers and storms
from the short term period will be exiting the area west to east
with a shift to northwesterly flow. This will advect cooler and
drier conditions into the area heading into the day on Saturday.
Subsidence and efficient mixing will certainly allow for a drop in
RH`s into the 30s, but luckily low-level winds will be fairly light,
not to mention the return of vegetation in most places. Heading
towards Sunday morning, focus will turn towards a developing Gulf
low, following the recent CAA. During the daytime, a shortwave will
approach from the west with increasing upper divergence as the jet
becomes centered over the northeast. The result will be increasing
PoPs, especially further south where better moisture exists. By
Monday morning, high pressure will be expanding from the west again,
which will produce additional subsidence. Depending on how much
cloud cover and MSLP gradient-induced winds linger, patchy frost
will be at least possible in the morning hours. Notable height falls
and recent CAA will keep temperatures fairly cool.
Tuesday through Thursday
High pressure will keep the area dry and mild on Tuesday. Heading
towards Wednesday, another shortwave will pass to the north with a
surface front also drifting southeastward from the central Plains.
This will lead to an increase in rain chances Wednesday and
Thursday. The overall pattern currently indicates a setup supportive
of showers with only limited thunder coverage due to fairly cool low-
levels. Moisture will also be fairly limited for the time of year,
given PWATs of only around 1 inch.
&&
.AVIATION...
(00Z TAFS)
Issued at 710 PM EDT Thu Apr 18 2024
Some showers and thunderstorms will be around at times especially
later tonight into Friday. Will carry tempo or prob30 thunder
groups for the times when probability looks highest, but timing
confidence is still not high. There is also a high chance (around
70 percent) that conditions will become MVFR at least for a
period Friday morning, so will include that as well all sites.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 65 80 57 73 / 80 40 10 20
Knoxville McGhee Tyson Airport, TN 63 75 54 68 / 80 80 20 10
Oak Ridge, TN 62 77 53 69 / 90 80 10 10
Tri Cities Airport, TN 56 73 51 66 / 50 80 20 10
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...
LONG TERM....BW
AVIATION...
Area Forecast Discussion
National Weather Service Paducah KY
644 PM CDT Thu Apr 18 2024
.KEY MESSAGES...
- Thunderstorms expected to develop this afternoon/evening.
Widespread damaging winds (30%) will be the prominent hazard
with the main line, while large hail (15%) and isolated
tornadoes (5%) may also occur.
- Much cooler Friday through the weekend, as highs/lows in the
80s/60s transition to 60s/40s. Some upper 30s are possible
both weekend nights, and if skies clear/winds diminish, some
frost potential exists then...with the better chance of that
occurring being Sunday night.
&&
.DISCUSSION...
Issued at 106 PM CDT Thu Apr 18 2024
We are closely tracking a warm front`s lift across the area, in
advance of a developing and approaching broader/stronger storm
system that will produce an all hazards potential severe weather
event later this afternoon/evening. Soupy upper 60s surface dew
points are in our south already, with lower 70s just about to
enter. As the warm sector lifts this pm, the increasing moist
tongue with temps rising into the 80s will help instability
balloon, with 2000-3000 J/KG Available Potential Energy for
Convection at most unstable in the layer.
CAMs all model active convection. Some (FV3/ARW) are a little
faster and more robust, while others (NAM) are on the opposite
end of that, but all agree on the main line approaching late
today and blasting thru the area this evening. The FV3/ARW
support an aggressive bowing of the northern structure of the
line, which is a slight evolution from previous runs. The HRRR
and NSSL also bow, but are more solidly split with warm sector
convection out ahead, and then main line convection with the
cold front`s approach. We still like a basic 18-21z warm sector
threat, followed by the main threat timing of the potential
bowing line from 21-03z.
After fropa, storm threat will diminish though some lingering
pop may survive thru the overnight. Low clouds may linger
til/shortly after daybreak, after which we`ll see that
cooler/drier air work its way in/across the FA. We are still
forecasting a transition from our 80s/60s highs/lows to 60s/40s
with this airmass change, that will last thru the weekend. Some
upper 30s are possible both weekend nights, with perhaps Sunday
night the better chance for frost with clearing skies/diminished
winds.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 644 PM CDT Thu Apr 18 2024
Scattered SHRA/TSRA could effect eastern portions of the region
early this evening, before a long line of strong to severe
storms sweeps quickly eastward across the entire region
beginning around 01Z and likely leaving the area by 06Z. Very
strong winds are likely with the main line of storms. MVFR
ceilings will arrive with the line and a period of IFR ceilings
may eventually develop overnight into the early morning hours.
Ceilings will lift to VFR by midday. South winds will shift to
the northwest behind the line of storms and gusts 20-25kts will
be possible through the remainder of the forecast.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
DISCUSSION...
AVIATION...DRS