Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/01/23
Area Forecast Discussion
National Weather Service Birmingham AL
1037 PM CDT Fri Mar 31 2023
...New SHORT TERM...
.MESOSCALE UPDATE FOR SEVERE WEATHER POTENTIAL...
Issued at 730 PM CDT FRI MAR 31 2023
A line of discrete supercells currently extends from east-central
Texas through west-central Tennessee, though are quite separated in
distance (compared to the northern portion of the overall mid
latitude cyclone). The northern-most supercell in our region is
near/north of I-40 in western Tennessee and has a history of
damaging tornadoes from Little Rock to northeast of Memphis.
Mesoanalysis indicates better low-level wind shear and moisture in
its current environment. Farther south, RAP mesoanalysis shows ML
LCLs rise to 1,000-1,250 m, indicative of drier PBL conditions, and
this is evident on our 00z RAOB. Our RAOB also depicts a capping
inversion ~700 mb. However, these LCLs should drop in the upcoming
evening hours, and instability should increase in Central Alabama as
the warm sector moves east with higher dewpoints. Environmental
parameters across this warm sector include 500-1,500 J/kg MLCAPE and
50-65 kts eff. bulk shear, supportive of the ongoing severe
thunderstorms and supercells we`ve seen so far today. 0-1 km SRH
is increasing to 300 m2/s2 across far northwest AL and the TN
Valley, and these values should increase to 300-400+ m2/s2 as the
925-850 mb jet increases during its upcoming nocturnal transition,
broadening hodograph curvature.
Throughout the evening hours, we`ll continue to watch these
discrete supercells as they move east. Latest hi-res guidance
indicates a parameter space supportive of their continued progress
toward Central AL overnight, though with a decrease in
instability and overall support aloft as they become more linearly
organized. Most favorable dynamics/cold air aloft remains well to
our north, and more appreciable height falls aren`t expected
across Central AL until after ~06z. In fact, current GOES-East
imagery is showing these supercell updrafts struggling to maintain
the rigor displayed during the late afternoon. Given the widely
spaced distribution currently observed, severe chances may be
trending down a bit. Nonetheless, we`re closely monitoring
conditions over the next few hours. If current strength maintains
or increases, there could be a need for a Tornado Watch for
portions of the area, mainly for our northwest counties where the
best overall parameters and dynamics are forecast into the
overnight. Stay tuned.
40/Sizemore
&&
.SHORT TERM...
(Tonight through Saturday)
Issued at 1015 PM CDT FRI MAR 31 2023
Finally starting to see some additional development south of
Memphis along the Mississippi River. There are still a few
supercells evident on local radars in Tennessee. Model depictions
overnight continue indicating a mix of supercell and QLCS
potential as it enters the northwest after midnight. SBCAPE
values are still forecasted to improve over Central Alabama in the
next 2-4 hours. Upper level westerly winds will increase, low
level jet winds will increase, Theta-e advection improves, SRh
values off local radars north are around 500 and Bulk Shear is
still high enough for organized severe. The best lift remains just
north of the area overnight. Therefore, the risk areas will not be
changed as the best potential for severe weather remains along and
north of I-20 overnight. It appears there will be a good chance of
at least a few supercells near the area. The timing has been
slower the past 6 hours, and will back up the timing once again.
Not mentioned anything until after midnight northwest. The focus
for the storms moves rather slow across the state and this leaves
a small potential for severe storms south into Saturday. Surface
based winds will also increase overnight outside of the storms.
These gusts may reach 40 mph at times. May have do expand the
timing on these gusts northwest farther into the night.
75
&&
.LONG TERM...
(Saturday night through next Thursday)
Issued at 231 PM CDT FRI MAR 31 2023
Long term forecast remains on track this afternoon, and the
previous discussion remains valid. Made minor adjustments to rain
chance and temps, but nothing that would change expected impacts.
Will hold off on adding anything in the HWO.
14
Previous long-term discussion:
(Saturday night through Thursday)
Issued at 342 AM CDT FRI MAR 31 2023
Quasi-zonal flow aloft temporarily sets up to start off the long
term period. High pressure will sink southward into Kentucky and
Tennessee, with northerly winds across Central Alabama becoming
light towards daybreak especially in sheltered locations. Can`t
completely rule out some patchy frost in the coldest far northern
locations Saturday night but most areas will remain in the 40s.
Pleasant conditions are expected for much of Sunday with
increasing high clouds during the afternoon. A relatively weak
southern stream shortwave currently off the coast of southern
California will eventually move across the area Sunday night and
Monday. There is still some model spread regarding the timing and
strength of this wave but overall expect increasing rain chances
late Sunday night into Monday morning with the highest chances
south with isentropic lift also occurring north of the warm front.
A few elevated thunderstorms will be possible but not expecting
anything severe at this time. Some surface-based instability does
develop in our southwest counties by Monday afternoon as the warm
front lifts northward, and while some isolated strong storms can`t
be ruled out this will be well behind the shortwave.
A vigorous shortwave and associated strong surface low will lift
northeastward from the Central Plains to the Upper Midwest Tuesday
and Tuesday night, with downstream ridging amplifying from the
Gulf to the East Coast. If a storm could develop Tuesday
afternoon it would be strong but currently expect the atmosphere
to remain relatively capped. At this time height falls with this
system look to remain northwest of the area. The pre-frontal line
of showers and storms will not arrive until very late Tuesday
night or more likely Wednesday morning. The LLJ will be weakening
through the morning Wednesday with flow becoming parallel to the
front. CAPE-shear parameter space would be potentially supportive
of at least isolated severe storms, but probabilities for a more
"organized" severe risk are too low to mention anything in the HWO
this far out. Southwest flow aloft will continue through the rest
of the week as ridging over the eastern Gulf causes the front to
stay in our vicinity, resulting in continued chances for showers
and storms. Will have to keep an eye on rainfall totals for any
flooding concerns.
32/Davis
&&
.AVIATION...
(00Z TAFS)
Issued at 735 PM CDT FRI MAR 31 2023
There were not many significant changes made this package. The
forecast trends were held together. The cold front and pre-frontal
line of convection approach the state around 06z. Ahead of these
features, winds will be gusty at times. Southerly winds will be 10-
20kts with some gusts as high as 30kts or so. Ceilings will drop
to MVFR from 04-06z. Thunder was mentioned as VCTS north and
PROB30 south. From 17z to 21z, clouds and rain chances decrease
northwest to southeast. Winds veer to the west at this time and
gusts to 20kts or so are possible until 00z.
75
&&
.FIRE WEATHER...
Showers and storms will move through the area tonight and
tomorrow morning, with drier air quickly spreading into the area
behind an advancing cold front. Min RH values will range from 25
to 35 percent Saturday afternoon, and 28 to 38 percent Sunday
afternoon.
Strong winds from the south today will become southwesterly by
early tomorrow morning, westerly by tomorrow afternoon, and
northwesterly by tomorrow evening. 20ft wind speeds up to
16-18mph can be expected during this time, before winds weaken
Saturday night.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 61 79 39 71 / 100 20 0 0
Anniston 64 79 42 72 / 100 40 0 0
Birmingham 64 79 43 72 / 100 20 0 0
Tuscaloosa 65 81 44 73 / 100 20 0 0
Calera 66 80 45 72 / 100 30 0 0
Auburn 66 81 47 72 / 30 70 0 0
Montgomery 68 83 48 73 / 40 60 0 0
Troy 68 83 51 76 / 10 60 0 0
&&
.BMX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 4 AM CDT Saturday for the following
counties: Fayette-Lamar-Marion-Pickens-Tuscaloosa.
Wind Advisory until 1 PM CDT Saturday for the following
counties: Blount-Calhoun-Cherokee-Clay-Cleburne-Etowah-Jefferson-
Randolph-Shelby-St. Clair-Talladega-Walker-Winston.
&&
$$
SHORT TERM...75
LONG TERM....14
AVIATION...75
Area Forecast Discussion
National Weather Service Corpus Christi TX
652 PM CDT Fri Mar 31 2023
...New AVIATION...
.SHORT TERM...
(Tonight through Saturday night)
Issued at 349 PM CDT Fri Mar 31 2023
Key Messages:
- Weak frontal boundary will stall across South Texas tonight.
- Patchy fog, possibly dense at times, each night.
- Above normal temperatures through the weekend.
- Isolated to scattered showers and thunderstorms across the west
Saturday.
A weak frontal boundary has been slow to move into the northwestern
CWA this afternoon, but is expected to drift into the area and stall
overnight. This will lead to light and variable winds tonight. The
general direction will east to northeast. Some lower dewpoints are
forecast to move into the LaSalle and McMullen counties, but the
remainder of the CWA will remain humid leading to the potential for
fog to develop. The SREF shows the best chance of fog with
visibilities less than 1 mile, along the coast with lesser chances
farther inland. The NAM and HRRR also indicate fog and dense fog
along the coast. However, other guidance just shows light fog. A
cloud deck is also expected, which will inhibit radiational fog from
developing. For now, have gone with patchy fog tonight across the
southern and eastern 2/3rds of the CWA and across the bays and
nearshore waters. If trends indicate visibilities lowering to less
than 1 mile across the waters and less than 1/2 a mile across inland
areas, then a Dense Fog Advisory may be needed later tonight.
The stalled boundary is expected to lift north as a warm front
Saturday afternoon or evening with winds veering to the east and
southeast. Moisture convergence along the warm front combined with
an mid/upper level short wave will contribute to isolated/scattered
showers and thunderstorms Saturday, mainly across the Rio Grande
Plains and Brush Country.
Despite the weak frontal boundary, temperatures will remain above
normal Saturday, but should be a couple of degrees cooler than
today`s values.
&&
.LONG TERM...
(Sunday through next Thursday)
Issued at 349 PM CDT Fri Mar 31 2023
Key Messages:
- Max temperatures likely to exceed 100 degrees Tuesday next week
from Live Oak/Kleberg (75%) to La Salle/McMullen (95%)
- Cold front Wednesday becomes rather stationary along the coast,
leading to showers and storms into the weekend
- Likely above normal precipitation (55-65%) April 6-10th
Quasi-zonal flow Sunday through Tuesday will lead to significant
warming as 850mb temperatures become very unusual with NAEFs
indicating 97.5-99.5th 850mb temperature percentiles and ECMWF
Extreme Forecast Index (EFI) 0.7-0.9. This will lead to maximum
temperatures in the triple digits mainly along and west of HWY-77
Monday and Tuesday. NBMv4.1 probabilities of max temperatures over
100 continues to range from 75 to 95% in the aforementioned area on
Tuesday. Maximum heat indices could exceed 105 over western Kleberg
into the Brush Country.
A strong closed mid-level low over the Rockies will deepen and move
east-northeastward across the Great Plains into the Upper Midwest
Tuesday into Wednesday. This will reflect a surface cold front
through South Texas Wednesday morning, reaching the coast in the
early afternoon with fairly good model agreement. Once the front
reaches the coast or nearshore waters, a coastal surface trough or
low is expected to form along the Middle to Lower Texas Coast. The
combination of a surface boundary, ample moisture advection with
PWATs around 1.9" (near max record), efficient 300K isentropic lift,
and a series of shortwaves aloft will lead to chances of showers and
at least a slight chance of thunderstorms Wednesday heading into the
weekend. A noticeable discrepancy between the GFS and ECMWF is the
position of the series of shortwaves aloft 850-500mb. The ECMWF is
the wetter solution with the shortwave positive vorticity advection
over South Texas owing to greater rainfall, whereas the GFS is
slightly shifted northward with less rainfall across South Texas.
Temperatures will cool significantly Wednesday into the latter half
of the week with the cold front, overcast skies and rainy conditions.
&&
.AVIATION...
(00Z TAFS)
Issued at 646 PM CDT Fri Mar 31 2023
While VFR conditions are in place at this time for all terminals,
expect CIGS to decrease for eastern sites through the evening and
overnight. MVFR to IFR conditions are expected. COT and LRD could
see some MVFR conditions for a few hours toward morning. VIS
restrictions are also possible east, mainly in the MVFR to IFR
range. Fog will be more prominent near the coast. A weak boundary
will be in the area tomorrow and a few showers, and maybe a
thunderstorm are possible for LRD and COT terminals. For now just
have SH in the TAFS, but may need to add TS tomorrow. Have MVFR
CIGS through the end of the period at CRP while other sites
improve during the late morning or afternoon. VCT has the
potential to stay MVFR as well, but currently expecting the
boundary to drift south of this site for a time, improving
conditions.
&&
.MARINE...
Issued at 349 PM CDT Fri Mar 31 2023
A weak to moderate southerly flow is expected tonight. Winds will
become northeast to east Saturday as a weak frontal boundary stalls
across the area. Weak to moderate east to southeast flow returns
Saturday night. A weak to moderate southerly flow is expected
tonight. Winds will become northeast to east Saturday as a weak
frontal boundary stalls across the area. Weak to moderate east to
southeast flow returns Saturday night. Moderate to occasionally
strong onshore flow of 15 to 20 knots is expected Sunday through
Tuesday night in advance of an approaching cold front Wednesday.
Shower and thunderstorm chances return Wednesday and will likely
continue into next weekend.
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 70 84 69 88 / 10 10 10 10
Victoria 66 85 66 85 / 10 10 10 10
Laredo 71 90 70 94 / 10 20 10 0
Alice 68 88 67 93 / 10 20 10 10
Rockport 69 81 70 82 / 10 10 10 10
Cotulla 66 90 70 95 / 10 20 10 10
Kingsville 69 87 68 92 / 10 10 0 0
Navy Corpus 71 79 70 82 / 10 10 0 10
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
SHORT TERM...TE
LONG TERM....EMF
AVIATION...PH/83
Area Forecast Discussion
National Weather Service State College PA
1119 PM EDT Fri Mar 31 2023
.SYNOPSIS...
A wet end to March for most as rain spreads west to east across
central PA through the evening and into tonight. Not an April
Fool`s joke: High winds and severe thunderstorms could knock
down trees and cause numerous power outages on Saturday. The
active weather will be driven in part by a large temperature
swing on the order of 30-40 degrees between Saturday afternoon
and Saturday night. Sunday will be the pick of the weekend with
decreasing wind and plenty of sunshine. Warmth will build
through early next week with temperatures surging well above
normal and feeling very spring-like.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Mid evening update. May cut down POPS a bit more here for
the period after Midnight. Most of the convection heading
northeast across western Lake Erie. One cell over central
Ohio.
Early evening discussion.
Made another small change early this evening. Based on rapid
decrease of showers on radar, lower POPS the next few hours to
match others.
More information below.
Main change late this afternoon was to lower temperatures and
wind speeds across much of the region. Clouds earlier resulted
in temperatures not warming much today.
Earlier discussion below.
Last day of March will feature showers through the evening. Max
12hr QPF ending 00Z Sat is fcst across the NW Alleghenies with
amounts in the 0.25-0.50" range. We don`t expect much rain to
fall to the southeast of I-81 thru 00Z. Max temps rebound +5 to
+15F from yesterday with highs in the upper 40s over the
northeast mtns to around 60F in the LSV.
Periods of rain continue tonight with some heavier downpours and
rumbles of thunder possible after midnight into early Saturday
morning. Big upward swing for min temps in the mid 40s-50s or
+15-25F warmer than last night and equally warmer than climo. We
also anticipate a non diurnal/rising trend overnight.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Made some large changes to timing of POPS and weather. First
front moves into the area during the morning, which may pull
a lot of the better moisture off to the east.
The second cold front moves into the area during the afternoon.
This front will have the dynamics to work with, but may be
hurting for low level moisture. The amount of clearing and
low level heating will be important. Main change was to have
a break between the two fronts.
Earlier discussion below.
Saturday (first day of trout season in Pennsylvania) looks very
windy with a dual severe t-storm threat and non-tstm high wind
hazard in play.
SPC has upgraded the convective outlook from level 1 to 2 out of
5 (Slight risk) given notable signal for a strongly forced low
topped line or cluster to race across at least part of the area
during the midday to afternoon timeframe. The 00Z 3km NAM and
HRRR depict the timing and evolution of this feature quite well.
Early morning rain should exit the eastern zones, followed by
clouds breaks allowing for very deep BL mixing and steep lapse
rates beneath the dry slot. This will be favorable for downward
momentum transfer of very strong mean flow >50kts 0-6km which
could result in a number of sfc wind gust of similar magnitude.
Despite lack of tree foliage, this scenario would likely result
in significant tree damage and potentially lead to numerous
power outages. Based on the latest hires guidance, it appears
the threat is maximized over the northern half of central PA.
In addition to the convective risk, a formidable and potentially
damaging non-tstm high wind event remains possible in the Saturday
afternoon-evening timeframe. Any preceding low topped convective
line should only enhance this risk given larger pressure rises
over a short duration. No change to the high wind watch for this
cycle with max gusts 55-60mph still focused over the Laurel
Highlands and south central Alleghenies. We would anticipate
making the call on high wind warning and wind advisory within
the next forecast cycle on the dayshift today. A wind advisory
is a virtual slam dunk at this point for most if not all of the
CWA.
Much colder, post-frontal WNW flow will deliver a rain to snow
shower transition across the western Alleghenies later Sat night
with a minor accumulation <1 inch possible by Sunday morning.
Building high pressure will bring an end to any lingering snow
showers across the western high terrain early Sunday, with
clearing skies and a noticeably cooler and drier airmass briefly
returning to close out the first weekend of April.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Not a lot of change to this section, some minor adjustments.
Overall still an active weather pattern for the lower 48.
Earlier disucssion below.
All guidance points to fair weather Monday, as high pressure
passes off the Mid Atlantic coast and an ensuing southwest flow
advects much warmer air into the state. A weak shortwave passing
north of the region should push a dying cold front into PA
Monday night, which is likely to stall over the region into
Tuesday. Low level convergence and a plume of anomalous pwats
along the front should support a fair amount of cloud cover and
the chance of showers esp NW Monday night and Tuesday. However,
lack of large scale forcing supports only limited POPs.
All medium range guidance supports very warm conditions midweek,
peaking on Wednesday, as the stalled front lifts north of the
state ahead of an upstream trough. Diurnal heating, combined
with falling heights ahead of the trough, should translate to an
increased chance of showers Wednesday during the day,
especially over the W Mtns. Ensemble mean 850mb temps around 11C
could support temps pushing 80F in southern valleys if there`s
enough sunshine.
Model spread and forecast uncertainty increase the second half
of next week regarding the timing of the upstream trough.
However, all guidance tracks the associated surface low well north
of PA, with a trailing cold front and potential showers coming
through in the Wednesday night to Thursday AM time frame. Temps
slip back toward seasonal norms by Friday.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
A moist southerly flow preceding an approaching cold front will
produce low cigs tonight, primarily where the flow is forced to
ascend the higher elevations of the N Mtns. Model soundings and
ensemble prob charts support a continuation of IFR/LIFR through
the night over the N Mtns. Elsewhere, expect conditions to
trend toward predominantly MVFR later tonight, associated with
showers arriving ahead of the approaching front. Another concern
will be the potential of low level wind shear associated with
the arrival of strong winds aloft. Bufkit forecast soundings
indicate it will a borderline case for reaching LLWS criteria.
Rapid clearing is anticipated behind the exiting cold front
early Saturday morning. However, increasingly gusty southwest
winds are expected to develop by Saturday afternoon ahead of a
more potent cold front approaching from the west. The cold
front, which should barrel through central PA between 18Z-22Z,
will be accompanied by a brief shower or thunderstorm in many
locations. Some of the storms could contain wind gusts between
40-50kts. Behind the front, strong westerly winds will impact
the entire area. Bufkit soundings support gusts to around 40kts
into the evening hours. Upsloping flow is also likely to yield
MVFR cigs and light snow showers across the W Mtns Saturday
evening.
Outlook...
Sun...Early AM low cigs possible Laurel Highlands.
Mon...No sig wx expected.
Tue...AM low cigs possible N Mtns.
Wed...AM low cigs possible eastern PA. PM tsra impacts possible,
mainly western PA.
&&
.CLIMATE...
With the last day of March upon us, here is a quick look at
monthly temperature, precipitation, and snowfall totals at
Harrisburg and Williamsport along with departure from normal.
Harrisburg through 3/30:
Avg. Temp = 42.9F (+1.3F)
Total Precipitation = 2.77 (-0.80")
Total Snowfall = T (-5.5")
Williamsport through 3/30:
Avg. Temp = 40.0 (+1.5F)
Total Precipitation = 2.53 (-0.49")
Total Snowfall = 6.6" (-0.6")
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 8 AM Saturday to 2 AM EDT Sunday for
PAZ004>006-010>012-017>019-025>028-034>037-041-042-045-046-
049>053-056>059-063>066.
High Wind Warning from 8 AM Saturday to 2 AM EDT Sunday for
PAZ024-033.
&&
$$
SYNOPSIS...Steinbugl/Martin/Gartner
NEAR TERM...Fitzgerald/Steinbugl/Martin/Gartner
SHORT TERM...Fitzgerald/Steinbugl/Martin
LONG TERM...Fitzgerald/Martin/RXR
AVIATION...Fitzgerald
CLIMATE...
Area Forecast Discussion
National Weather Service Cheyenne WY
713 PM MDT Fri Mar 31 2023
.UPDATE...
Issued at 703 PM MDT Fri Mar 31 2023
Gusty winds continue at CYS and points east, therefore, the High
Wind Warnings for Laramie County, and Kimball and Cheyenne
counties in Nebraska have been extended until 03Z. The Winter
Storm Warning for Dawes County and Advisories for northern Sioux
County and Box Butte County were allowed to expire, though light snow
may persist for a few hours. Additionally, the High Wind Watches
starting at 15Z Saturday for northwestern portions of the CWA were
upgraded to High Wind Warnings and Bordeaux was added.
&&
.SHORT TERM...(Today - Sunday)
Issued at 222 PM MDT Fri Mar 31 2023
A very windy day across much of the Interstate-80 corridor between
Rawlins and Sidney. The usual wind prones of Arlington and the south
Laramie Range and foothills have been consistently gusting in the
upper 50s and low 60s, verifying the High Wind Warnings for these
areas. Even central Laramie County has been hitting wind gusts over
58 MPH, verifying the Warning. Added east Laramie County, Kimball,
and Cheyenne County into a High Wind Warning for this afternoon as
Hi-Res guidance showed winds creeping up this afternoon due to winds
aloft strengthening. Hi-Res guidance shows winds easing this evening
below high wind criteria due to the weaker mixing potential and
increased cloud cover. Warnings from Cheyenne over to Sidney expire
at 00Z Saturday.
High Wind Warnings continue for the wind prones already in effect
through Saturday evening. 700 mb CAG-CPR height gradients remain
elevated through Saturday night which will help support the 55 to 60
kt winds aloft through the day. There is the possibility that these
Warnings will need to be extended into Sunday morning as the height
gradients, winds aloft, and downward omegas support high winds
through Saturday night.
High winds look to become more widespread late Saturday afternoon as
flow becomes more zonal with a 100 kt jetstreak and associated upper-
level disturbance just north of the CWA. 700 mb winds aloft look to
max out around 70 kts with this more widespread event. This event
looks like an excellent mountain wave set-up based on the 500 mb
height pattern and the omega field. Based on wind gusts seen today,
would not be surprised if some locations see gusts over 70 MPH. The
best spot to see some of these stronger gusts would be along the
Interstate-25 corridor between Chugwater and Glendo. Based on this,
added east Platte County to the current High Wind Watches in effect
tomorrow through Sunday. Bordeaux will likely also be considered for
some sort of wind headline as well, and potentially areas further
east. Winds will likely ease Sunday afternoon as gradients weaken.
Aside from winds, the rest of the weekend shouldn`t be too bad as
the zonal flow will keep the area relatively mild. Looking at highs
mostly in the 50s for areas east of the Laramie Range and 30s to 40s
for areas to the west. Clouds will be on the increase during the day
Sunday, especially areas to the west. Moist west to southwesterly
flow ahead of the next system will lead to light snow developing
over the mountains during the day on Sunday.
.LONG TERM...(Sunday Night - Friday)
Issued at 222 PM MDT Fri Mar31 2023
...POTENTIALLY HIGH-IMPACT WINTER STORM WILL IMPACT PORTIONS OF
SOUTHEAST WYOMING AND THE WESTERN NEBRASKA PANHANDLE EARLY NEXT
WEEK...
Medium-range deterministic models as well as GEFS/EPS members have
come into better agreement w/ regard to the overall evolution of a
potentially significant storm system poised to impact a large part
of the region through the extended forecast period. Models suggest
an intense 120+ knot H25 jet streak digging rapidly south and east
along the west coast of California from Sunday night through early
Monday, carving out of a sharp western US trough which will likely
rapidly deepen over the 4 Corners by mid-day Monday. Rapid surface
cyclogenesis will be well underway over northeastern Colorado late
Monday afternoon in response to deep, strongly difluent flow aloft
in advance of the approaching system. Models are in good agreement
with a sub-990 millibar Colorado Low initially developing over far
east central Colorado, then drifting ENE across northwest Kansas &
south central Nebraska from Monday Night through Tuesday. Analysis
of low positions from various Ensemble systems suggests models are
now in significantly better agreement with regard to the track and
overall intensity of the surface cyclone. Confidence appears to be
increasing that at least some portion of the CWA should experience
significant winter impacts from this system, although the expected
storm track would tend to favor areas north of I-80 but especially
east central Wyoming into the northern Nebraska Panhandle.
Snow will begin developing over western areas late Sunday night w/
a more notable increase in coverage and intensity expected Monday/
Monday night as intense & persistent low-level frontogenesis takes
shape in the right entrance region of a 125-knot 250 mb jet. Quite
the impressive fetch of Pacific moisture available to this system,
with the NAEFS suggesting IVTs above the 90th percentile extending
from the coast of southern California to southeast Wyoming. BUFKIT
soundings suggest deep column saturation with very steep mid-level
lapse rates, along with significant omega through an impressive 5-
10k foot dendritic layer. Significant low-level convergence should
be present along a SW-NE oriented near-surface frontal zone, which
should set up roughly from the central Laramie Range northeastward
toward CDR. Deep low-level warm air advection & isentropic upglide
will be present along this boundary, which will most likely become
oriented parallel to the mid & high level moisture plume. Snowfall
rates will be intense in the vicinity of this boundary, perhaps in
excess 2 inches per hour. The exact placement of this boundary may
be paramount in which areas are most significantly impacted, maybe
even resulting in freezing drizzle south of the boundary w/ warmer
low levels limiting ice crystal growth. However, all areas along &
north of the boundary will see significant snowfall. Heaviest snow
should fall late Monday through early Tuesday w/ some accumulation
lingering into Tuesday night.
Deterministic runs of the GFS/ECM/GEM & even the UKMET are showing
excellent agreement w/ a swath of 1 to 3 foot snowfall amounts for
areas along and north of a line from Rawlins-Chugwater-Alliance w/
a very sharp cutoff along the I-80 corridor in far southeast Wyo &
the southern Neb Panhandle. GEFS members suggest 80+ percent probs
of 6+ inches along this same corridor using a 10:1 ratio, with 50+
percent probs of 12+ inches. Latest European ENS members are quite
similar to the GEFS. Further, GEFS plumes for Chadron show notable
clustering between 1.5 and 2.5 inches of QPF, although we do still
have a good bit of spread indicating significant uncertainty. Even
so, confidence is rapidly increasing that snowfall totals could be
measured in feet for many areas between Monday and Tuesday. Latest
NBM v4.1 shows 50+ percent probs for 6 or more inches of snow over
the entire CWA with 15 percent probs of 24+ inches from Converse &
Niobrara counties into the northern Nebraska Panhandle, especially
along the Pine Ridge. 50th %iles come in at a minimum of 5-8+ inch
amounts w/ 12-15 inch amounts over the northern tier of zones. Our
confidence is quite high that snowfall will be measured in feet in
much of the area, although the biggest challenge right now will be
pinning down the precise location of the surface boundary.
Wind gusts 35-40 MPH will also be possible with the strong surface
pressure gradients in place, so blowing snow will be an issue even
for an early April event. Highly anomalous 700-mb temperatures at/
below -12 deg C suggests surface temperatures in the lower 20s and
general thermal profiles supporting 15 or 18 to 1 ratios. Could be
tough to get true blizzard criteria based on current data, but the
impacts will still be significant w/ severe blowing/drifting quite
likely. While overall confidence has increased significantly, will
wait to analyze a few more model cycles prior to issuing headlines
for this event. Winter Storm Watches will likely be necessary very
soon.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 520 PM MDT Fri Mar 31 2023
Still dealing with low flight conditions across the northern
Nebraska Panhandle at KCDR and KAIA for a for more hours this
evening. KCDR and KAIA have been reporting IFR/LIFR conditions in
snow. Latest HRRR and RAP mesoscale guidance pulls this snow east
after roughly 02Z...so VFR conditions shortly after that. Winds
ease towards sunset with VFR conditions the remainder of each TAF.
&&
.FIRE WEATHER...
Issued at 229 AM MDT Fri Mar 31 2023
No fire weather concerns this weekend and through most of
next week as a few Pacific storm systems push across the Rocky
Mountain Region and adjacent plains. These storms will bring strong
winds, a good chance for accumulating snow, and colder temperatures.
A brief warm up is expected this weekend with daytime humidities
lowering to around 20 to 30 percent each afternoon.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until 9 PM MDT this evening for WYZ118-119.
High Wind Warning from 9 AM Saturday to noon MDT Sunday for
WYZ101-104>107-109.
High Wind Warning until noon MDT Sunday for WYZ110-116-117.
NE...High Wind Warning until 9 PM MDT this evening for NEZ054-055.
&&
$$
UPDATE...AM
SHORT TERM...SF
LONG TERM...CLH
AVIATION...GCC
FIRE WEATHER...TJT
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
753 PM EDT Fri Mar 31 2023
.UPDATE...
During the next two to three hours, there will be a rapid increase in
ascent across Se Mi as a 60-70 knot low level jet noses into Se Mi.
This increaed low level inflow will drive elevated instability
(possibly up toward 1200 J/kg of CAPE). The 00Z DTX sounding, latest
ACARS soundings from srn Lower Mi and nrn Indiana, and most recent
RAP soundings suggest a fair amount of boundary layer stability will
prevail through at least 06Z. This will make it challanging for
severe wind gusts to reach the surface. However, with this amount of
elevated instability and extremely strong forced ascent, large hail
(greater than one inch diameter) is going to be a concern with the
storms tonight. This will be especially true across the southern half
of the forecast where there will be a higher degree of elevated
instability. The storm reports out of northern Indiana have also been
primarily large hail. In terms of the forecast itself, it remains
valid. The only change will be to add some fog across the Saginaw
Valley and thumb region this evening.
&&
.PREV DISCUSSION...
Issued at 638 PM EDT Fri Mar 31 2023
AVIATION...
A rapidly deepening low pressure system will track across eastern
Iowa and into southern Wisconsin this evening. Intense low level wind
fields will lift across Indiana into Srn Lower Mi this evening.
While these winds will largely be elevated and thus inhibit strong
sfc gusts, they will drive a plume of deep layer moisture and
elevated instability across Se Mi. This will result in widespread
rain with scattered thunderstorms. The latest hi res suite continue
to suggest thunderstorm timing will be between 02Z and 05/06Z across
Se Mi. The warm front that lifted into the I-69 corridor this
afternoon now appears to have become stationary. Ongoing low level
moisture transport across this frontal system has already allowed IFR
and lower conditions from PTK northward with some VLIFR conditions
across MBS, conditions that will prevail through the evening.
As the sfc low lifts toward northern Lake Mi overnight, a strong
push of subsidence will expand across Se Mi in the wake of the
occluded front. This is likely to scour low clouds out and will end
showers/thunderstorms after 06/07Z. Model soundings suggest a weak
near sfc stable layer may keep peak wind gusts within the post
frontal environment overnight at or below 25 knots, even though 2-3k
ft wind speeds will be 45 to 50 knots.
For DTW...The region of thunderstorms upstream is expected to
traverse the metro area between 02Z and 04Z. There may be a brief
break in the convection between 04Z and 05Z before a line of
convection moves across the area in the 05Z to 06Z time frame.
DTW THRESHOLD PROBABILITIES...
* High in ceilings below 5000 feet this evening and on Saturday. Low
overnight.
* Moderate in thunderstorms this evening.
PREV DISCUSSION...
Issued at 425 PM EDT Fri Mar 31 2023
DISCUSSION...
Thunderstorm potential tonight is the primary issue in this forecast
cycle as a powerful low pressure system migrates across the Midwest
and Great Lakes. Afternoon observations show the warm front making
northward progress through southern Lower MI at pace close to model
estimates. Generous coverage of warm sector clouds also follows the
general model trend of both coverage and boundary layer stability
estimates. Warm sector stability is also holding up well against the
peak of meaningful late March/early April daytime heating, judging
by the wave texture in low clouds shown in visible imagery, and
likely with further support from lingering mid level subsidence
associated with the short wave ridge. HREF forecasts of surface
based CAPE and individual model soundings show surface/boundary
layer stability then holding as ongoing IL/IN convection reaches
Lake MI and SW Lower MI around 00Z. Zero surface based CAPE is then
projected after 00Z over all of SE MI while MUCAPE fails to reach
1000 J/kg. This supports the elevated case and less severe potential
this evening while a new round of moisture transport/theta-e
advection maintains coverage and moderate intensity. That leaves
storms along the cold front as the final concern for any severe
conditions tonight as it moves into the region toward midnight.
Closer examination of forecast soundings across hi-res model
membership indicates a few hours of near neutral boundary layer
thermal profiles. This suggests enough potential to monitor for
damaging wind gusts in any storms that can remain organized near the
Ohio border while the front itself is also capable of a few 40 mph
wind gusts across the rest of SE MI.
The front sweeps showers and thunderstorms out of Lower MI not long
after 06Z tonight. Low to mid level cold advection and associated
gusty wind potential then follows for the late night into Saturday
morning. At first glance, the wind field appears strongly forced by
the intense mid level circulation/vort max, although the surface
based stable layer mostly holds or is reestablished during the late
night pointing to low level cold advection and momentum transport
somewhat disrupted by elongation of the surface pressure pattern.
For the rest of Saturday, cloud and precipitation character become
cold core dominated during Saturday as the mid level trough axis
moves nearly overhead by afternoon. Forcing associated with the
primary vorticity maximum is accompanied by 500 mb temperature
dropping to around -25C, both of which support renewed coverage of
showers during the morning through about mid afternoon and then
ending as the system exits eastward.
High pressure building into the region Saturday night lasts through
Sunday. It brings dry weather at the expense of slightly below
normal temperatures, especially by Sunday morning as the day starts
off after lows in the mid to upper 20s. This is followed by a quick
temperature rebound to start next week as a new long wave ridge
builds over the Midwest and Great Lakes. Guidance high temperatures
return to around 60 Monday and make a run toward 70 by Wednesday.
MARINE...
A warm front associated with a strong low pressure system across the
upper Mississippi Valley will continue lifting slowly northward
through the central Great Lakes into tonight. Meanwhile, the surface
low will track further northeastward from central Lake Michigan this
evening, to central Lake Huron tonight, and eventually into the St.
Lawrence River valley by late in the day Saturday. The strong low
pressure system will further deepen into the mid 980s hPa with the
system`s powerful cold front sweeping through the local waters late
tonight and into early Saturday morning. As the surface low tracks
across the Great Lakes, it may break off into two distinct low
pressure centers with impressive dynamics in place.
Continued northward transport of warm, moist air will lead to fairly
stable over-lake conditions across the local waters with prevailing
southerly flow limited to gusts below gales through the first half
of tonight. As the center of the low approaches tonight, winds will
turn northeasterly across the northern Lake Huron basin and
southwesterly across the remaining local waters. Strong cold air
advection behind the cold front passage along with a northerly wind
shift will lead to a period of gales across all of the local waters,
with the strongest winds across the open Lake Huron basin. Gale
Warnings are in effect for all of Lake Huron, Lake St. Clair, and
western Lake Erie late tonight through late Saturday evening.
Widespread rain with embedded thunderstorms will be possible as the
low pressure system tracks across the region this evening and
through tonight. Especially across the far southern half of Lake
Huron, Lake St. Clair, and western Lake Erie, there is a low
potential for thunderstorms to produce gusty winds in excess of 35
knots with a strong low-level wind field in place. The best
potential for this occurrence will be from 8pm-2am.
Wind speeds will rapidly decrease Saturday night as high pressure
from the upper Midwest builds into the Great Lakes and ends the
threat for gales. As the high pressure drifts southeast throughout
the day Sunday, another low pressure system moving across the
northern Great Lakes Monday will bring an increase in winds speeds
again approaching gale strength.
HYDROLOGY...
A strong low pressure system tracking through the central Great
Lakes brings another round of showers and a chance of thunderstorms
tonight. Additional rainfall totals of 0.25 to 0.75 inch are
expected, combined with similar amounts from this morning, for event
totals of 0.75 to 1.5 inches before the system exits late tonight.
The flood hazard remains minimal in this event, especially given the
lengthy afternoon break affording drainage a chance to keep pace.
Ponding of water on roads and minor flooding of prone poor drainage
areas remain possible. Within-bank rises on area rivers and streams
is also likely and which will continue through the weekend.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Warning from 4 AM to 10 PM EDT Saturday for LHZ361>363-421-422-
441>443-462>464.
Dense Fog Advisory until 4 AM EDT Saturday for LHZ361>363-421-422-
441>443-462>464.
Lake St Clair...Gale Warning from 4 AM to 10 PM EDT Saturday for LCZ460.
Michigan waters of Lake Erie...Gale Warning from 4 AM to 10 PM EDT Saturday for LEZ444.
&&
$$
UPDATE.......SC
AVIATION.....SC
DISCUSSION...BT
MARINE.......IRL
HYDROLOGY....BT
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Fort Worth TX
640 PM CDT Fri Mar 31 2023
...New Short Term, Aviation...
.SHORT TERM... /NEW/
/Tonight through Saturday Night/
A powerful storm system continues to move through the central
CONUS tonight with a severe weather outbreak underway across parts
of the Mid-South and Midwest. The tail end of this activity is
draped across the far southeast parts of our CWA where a strong
Pacific cold front is moving through. Latest RAP objective
analysis indicates around 2000 J/kg of MLCAPE in this area which
continues to support robust updrafts and a few strong/severe
cells. This activity will move out of our area in the next hour or
so and we`ll be done for the rest of the night through Saturday.
In the wake of the frontal passage, much drier air has filtered
into North Texas with dewpoints in the teen and 20s along with
brisk westerly winds. These winds will diminish in the next couple
of hours as we lose daylight, but areas of blowing dust across
West Texas have spread into the region and skies will likely be
hazy for a few hours.
Cooler air behind the actual cold front will spill southward early
Saturday morning resulting in northerly winds. Other than some
passing cirrus through the day, Saturday is shaping up to be a
nice day with highs in the 70s and low humidity.
Dunn
&&
.LONG TERM... /Issued 145 PM CDT Fri Mar 31 2023/
/Sunday and Beyond/
An active and complex weather pattern is expected next week across
North and Central Texas. As a ridge slides east of the area and a
trough approaches from west this weekend, southerly flow will return
and bring warm, moist air into North and Central Texas by Sunday.
The front expected to push through our area today (Friday) will
reverse and advance northward as a warm front by Sunday afternoon.
Daytime heating, dryline development, the advancing warm front, and
an approaching shortwave embedded in the flow may provide the
ingredients for thunderstorm development Sunday afternoon and
evening. At this time, hail and damaging winds would be the
primary hazards. Keep in mind that the timing of each of these
features may modify the forecast. With the loss of daytime heating
and the exiting shortwave, rain/storm chances will diminish by
Sunday night.
By Monday into Tuesday, a large-scale trough across the western
CONUS will approach and a surface low will develop north of the
region, which will yield a tight gradient and usher in gusty
southwest winds. Expect temperatures to be well above normal
Monday and Tuesday across Texas. Elevated to near critical fire
weather concerns should be expected on Tuesday in particular,
especially west of the I-35 corridor where strong southwesterly
winds, above normal temperatures, and low relative humidity values
are expected.
There remains some uncertainty in the broad trough progression this
far out, but expect a cold front to push into North and Central
Texas in the late Tuesday/early Wednesday time frame. Several
embedded shortwaves will also yield a wet pattern for the latter
half of the week as well.
Schroeder
&&
.AVIATION... /NEW/
/00Z TAFs/
VFR will prevail through the period with westerly winds
diminishing after sunset. Some haze from blowing dust will reduce
visibilities slightly through this evening, but these should
improve after dark. A wind shift to the north is expected around
sunrise as a cold front spills southward. VFR will prevail on
Saturday with light northerly flow becoming more easterly late in
the day. Outside of the gusty winds this evening and blowing dust
to the west, no significant aviation concerns are expected through
Saturday.
Dunn
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 53 74 54 78 63 / 0 0 5 50 20
Waco 49 76 53 81 64 / 0 0 5 40 20
Paris 50 71 46 73 60 / 0 0 0 50 30
Denton 48 72 49 76 59 / 0 0 0 50 20
McKinney 48 72 49 75 62 / 0 0 0 50 20
Dallas 54 75 54 78 64 / 0 0 5 50 20
Terrell 50 73 51 78 63 / 0 0 5 50 30
Corsicana 51 76 54 81 65 / 0 0 10 50 20
Temple 48 80 54 82 64 / 0 0 5 40 10
Mineral Wells 47 75 51 82 57 / 0 0 0 50 10
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Grand Rapids MI
755 PM EDT Fri Mar 31 2023
LATEST UPDATE...
Aviation
.DISCUSSION...(This evening through next Friday)
Issued at 343 PM EDT Fri Mar 31 2023
-- Slight Risk of Severe Thunderstorms Late Evening --
Broad consensus from the HREF and WoFS that the thunderstorm complex
in western IL as of 3 pm will move into far southwest Lower MI
around 7 pm, followed by a broken line of thunderstorms ahead of the
cold front a few hours later. These will primarily be supported by
warm air and moisture transport in the 900-800 mb layer from a 50-60
knot low-level jet, and lifted/cooling air ahead of a deepening mid-
level cyclone.
The substantial low-level and deep-layer shear with an increasingly
high momentum synoptic low-level wind field does bring concern for
severe weather in southern Lower Michigan this evening. However the
threat for tornadoes and widespread severe wind gusts will be
suppressed a little by a weakly stable near-surface layer (and more
stable to the north of I-96 where there is a stationary surface
front). One big question is how much convective inhibition above 800
mb will prevent widespread weaker convective development that would
interfere with a potentially strong mesocyclone or two arriving in
SW Michigan from Illinois after 7 pm, as depicted in the 18Z HRRR
and WoFS. With either the LLJ convection or the cold frontal
convection, it`s plausible that stronger updrafts capable of
producing hail entraining with pockets of dry mid-level air would
result in downdrafts capable of reaching the surface.
See the Hydrology section for information about the potential for
flooding.
-- Windy in Spots Late Tonight and Saturday --
Just behind the cold front underneath clearing skies late tonight, a
west-southwesterly jet of 40 to 45 knots just 1000 feet off the
surface may result in strong winds for a brief time in parts of West
Michigan. Contemplated a short duration wind advisory for this but
despite the cold air advection, the low-level lapse rates right near
the surface do not appear to be unstable enough to promote frequent
strong gusts.
Mid day Saturday, a jet of strong north winds on the back side of
the low pressure system developing over mid Lake Michigan may skirt
the lakeshore and impact areas south of Holland toward St Joseph. A
wind advisory may be needed there if confidence builds in the HRRR
solution.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 755 PM EDT Fri Mar 31 2023
Isolated storms have formed out ahead of the approaching line and
has brought TSRA to GRR and AZO. Storms will be in the vicinity
of BTL and MKG by 01Z. Expect rounds of showers and storms through
the evening with IFR to LIFR cigs and vsbys in TSRA between now
and 06Z. LLWS should occur at all TAF sites from O5Z to 11Z. After
06Z MVFR will return though cigs could drop in isolated storms
overnight. Conditions will improve Saturday however post frontal
MVFR and gusty wind will be expected after 14Z tomorrow.
&&
.MARINE...
Issued at 205 PM EDT Fri Mar 31 2023
Other than the wind gusts on Lake Michigan that may occur with
thunderstorms between 7 PM and midnight, there are two periods of
gales that are of concern through Saturday. First is the potential
for west-southwest gales after the storms and cold front clear
late tonight. There may be a lull in the gales part of Saturday
morning, then gales to 45 knots from the north are likely late
Saturday morning through the afternoon on the back side of the
exiting low pressure system.
&&
.HYDROLOGY...
Issued at 343 PM EDT Fri Mar 31 2023
The first round of rain that came through West Michigan this
morning has dropped between 0.5 and 1.0 inches of rain across most
of the area. A 2nd round of rain is on track for this evening,
with similar amounts of rain (0.5 to 1.0) expected again. All of
this water will find its way to the streams and rivers in the area
over the next few days. While this will bring several rivers to
bankfull, the places we think are most likely to see some minor
flooding are along the Muskegon River downstream of Croton Dam
(Newaygo and Bridgeton).
Depending on where the strongest thunderstorms track this evening,
it`s also possible that a few bullseye locations could see
additional rain amounts closer to 2 inches tonight. If this happens,
it`s possible some general (areal) flooding could occur as well.
Probably this would primarily cause some overflow in the smallest
creeks and streams, as well as resulting in standing water on roads
and in poor drainage areas. While it`s hard to know where this is
most likely to happen, it would probably be along one of the
lakeshore counties, as these storms will overall be weakening as
they track eastward.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 11 PM EDT this evening for LMZ844>849.
Gale Warning from 11 PM this evening to 8 PM EDT Saturday for
LMZ844>849.
&&
$$
DISCUSSION...CAS
AVIATION...Ceru
HYDROLOGY...AMD
MARINE...CAS
Area Forecast Discussion
National Weather Service Lincoln IL
852 PM CDT Fri Mar 31 2023
.SYNOPSIS...
Issued at 852 PM CDT Fri Mar 31 2023
A line of thunderstorms will continue to track eastward across the
I-57 corridor into Indiana late this evening. After that, expect
windy and dry weather for the remainder of the night.
&&
.UPDATE...
Issued at 852 PM CDT Fri Mar 31 2023
0145z/845pm radar imagery shows a line of strong to severe
convection extending from Danville...to Shelbyville...to near
Salem. The storms are quickly tracking off to the east-northeast
and will push into Indiana after 03z/10pm. Damaging wind gusts and
isolated tornadoes will be possible. Once the storms end, gusty
westerly winds will bring sharply colder/drier air into central
Illinois with overnight low temperatures ranging from the middle
30s along/west of I-55...to the lower to middle 40s along/south of
I-70.
&&
.SHORT TERM...(This evening through Saturday)
ISSUED AT 336 PM CDT Fri Mar 31 2023
20z/3pm mesoanalysis shows a moderately unstable/highly sheared
warm sector environment characterized by MLCAPEs of 1000-1500J/kg
and 0-3km shear in excess of 40kt west of the I-55 corridor.
Several clusters of strong/severe convection are ongoing...with
most of the activity now along/north of a Macomb to Bloomington
line. Based on radar trends and HRRR forecasts, it appears this
convection will exit the northern KILX CWA into northern Illinois
within the next 1-2 hours. After a brief lull, additional cells
firing further upstream ahead of an advancing cold across central
Iowa/Missouri will quickly pivot into the area by late
afternoon/early evening. Most CAMs suggest the cells will congeal
into a squall line, then race eastward into Indiana by 9pm-10pm.
The primary threat with the line will be damaging wind gusts in
excess of 70mph: however, a few tornadoes will also be possible.
Once the cold front passes and the storms depart, winds will veer
to the west and temperatures will plummet. Readings will drop from
current values in the upper 60s and lower 70s to early morning
lows ranging from the middle 30s in the Illinois River Valley to
the middle 40s south of I-70. Blustery and chilly conditions will
prevail on Saturday as the pressure gradient tightens between
departing low pressure and a high building into the Plains.
Forecast soundings and numeric guidance indicate W/NW gusts
reaching 40-50mph Saturday morning before gradually subsiding
during the afternoon. High temperatures will be considerably
cooler than today...only reaching the middle to upper 40s.
.LONG TERM...(Saturday night through Friday)
ISSUED AT 336 PM CDT Fri Mar 31 2023
Quiet weather will be on tap for Sunday as temperatures quickly
rebound back to seasonal values in the upper 50s and lower 60s. As
a weak front drops southward and stalls in the region, low chance
PoPs for showers are warranted Sunday night into Monday.
After that, attention turns to another powerful storm system
progged to track from the southern Rockies into the Upper Midwest
early next week. As the upper system approaches from the west, the
stationary frontal boundary will lift back northward as a warm
front on Tuesday. Given increasing instability/shear, there will
be a risk for strong to severe storms Tuesday/Tuesday
night...before a cold front sweeps through Illinois by early
Wednesday morning. At this time, will focus highest PoPs Tuesday
afternoon and evening, with rapidly decreasing rain chances by
Wednesday. High temperatures will soar into the middle to upper
70s on Tuesday, but will drop back into the lower to middle 50s by
Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 700 PM CDT Fri Mar 31 2023
Primary line of strong to severe convection is taking shape along
the I-55 corridor early this evening...with a secondary line
northwest of the Illinois River. Based on radar trends, it appears
the storms will arrive at KDEC/KCMI by 01z, then push east of the
terminals by 02z. The line further northwest appears it will brush
KPIA over the next hour, then lift northeastward out of the area.
Once the convection departs, winds will veer to the west and gust
30-35kt through midnight. Winds will likely temporarily decrease
overnight before the pressure gradient tightens and W/NW gusts
increase to 35-45kt by Saturday morning. Winds will remain
strong/gusty through the afternoon before diminishing toward
sunset. VFR ceilings are expected tonight: however, MVFR ceilings
poised to the northwest will filter southward into the area by
morning. Based on HRRR/NAM forecast soundings, have introduced
MVFR at KPIA by 11z, then further southeast to the I-72 sites by
13z.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 1 PM CDT Saturday for ILZ027>031-036>038-
040>057-061>063-066>068-071>073.
&&
$$
UPDATE...Barnes
SYNOPSIS...Barnes
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Barnes
Area Forecast Discussion...UPDATED
National Weather Service Indianapolis IN
945 PM EDT Fri Mar 31 2023
.Mesoscale Update...
Issued at 945 PM EDT Fri Mar 31 2023
The supercell in Clay County, Illinois should reach Sullivan and
Vigo County by 10:30pm. Latest KVWX VWP-derived hodograph shows a
very favorable low-level shear environment for supercells and
tornadoes. Continued 2-m theta-e advection and large scale ascent
from approaching trough may effectively erode current area of
inhibition on the Indiana side of the state line. Eventual merging
with the surging QLCS is expected, but until then there may be at
least a small window spatiotemporally for tornadoes, albeit
somewhat low probability given thermodynamic limitations mentioned
above, at least into Sullivan County.
Additional convection southwest of our area will continue to merge
and move northeastward impacting Knox, Daviess, and Martin
counties also by approximately 10:30pm.
&&
.Mesoscale Update...
Issued at 842 PM EDT Fri Mar 31 2023
Deep closed low is currently located over eastern Nebraska and is
moving eastward now. Intense DCVA and associated strong forcing will
primarily track over the northern portion of the area into the
southern Great Lakes and this should be where a more
intense/widespread wind threat should evolve, from the line of
convection in northwest Illinois. Further south, trailing more
positively tilted vort maxima and still appreciable midlevel height
falls will likely still be sufficient for linear evolution with
time. Another factor favoring at least a quasi-linear trend is
veered low level flow and generally straight hodographs supporting
splits and cell mergers which have been observed over western
Illinois the last hour or two.
0-3-km shear vector orientation is more parallel to these
southernmost segments that will impact much of central Indiana into
the evening, somewhat limiting the QLCS mesovortex/tornado threat
some. Nevertheless, any embedded mesocyclones or localized surges
and resultant line reorientations will need to be watched closely
for tornado potential. Even if shear vector orientations aren`t
optimal, the magnitude of shear is particularly high and can
compensate.
Latest ACARS from IND shows a trend toward stronger ascent with
cool/moist PBL below capping EML deepening as CIN decreases. Near-
term model guidance continues to show a fairly narrow corridor of
enhance instability and little/no inhibition ahead of the QLCS. In
fact, thermodynamic profiles may be quite favorable for deep
coupling with stronger momentum aloft, and strong winds (locally
significant). Wind damage continues to be the main threat.
&&
.Mesoscale Update...
Issued at 646 PM EDT Fri Mar 31 2023
Latest ACARs soundings and the 21Z HRRR 0 hour forecast soundings
are both showing that the previously mentioned cap at 850mb is
eroding away with only a minor bump noted at 2235Z. Parcels are
still not surface based, but this won`t stop any ongoing storms that
move into the area. Thoughts from earlier this afternoon are still
in line with the main timeframe for severe weather being from 9PM to
12AM.
Latest radar imagery shows a line that has become to congeal across
western Illinois into Missouri with widespread severe weather being
reported along the line. With Indiana well within the exit region
of the jet and a strong push of southwesterly flow behind the line,
there shouldn`t be any problem keeping this complex together as it
arrives into Indiana. Models are maintaining the thought that the
thermodynamic profiles will be favorable by the time of storm
arrival.
Relevant portions of previous discussions below....
A sounding from Purdue in Lafayette showed at around 545PM the cap
that was advertised earlier remains in place with good shear.
Instability remains generally locked above the cap. Latest ACARs
soundings over IND show a similar profile. Expectations are that
this will erode between 6PM and 8PM with the severe threat rapidly
ramping up afterwards.
Expect additional discussions through the evening.
&&
&&
.Short Term...(This evening through Saturday)
Issued at 301 PM EDT Fri Mar 31 2023
***SEVERE WEATHER EXPECTED TONIGHT***
- Central Indiana now under a MODERATE RISK for severe weather.
- Main Severe Threat tonight will be damaging straight line winds to
70 mph
- Showers/Storms Possible late this afternoon
- WIND ADVISORY 800 PM - Sat 500 PM
Surface analysis this afternoon shows deep low pressure in place
over western IA. This was providing a quick southwest flow in place
across Indiana and the Ohio Valley. Dew points have crept into the
lower 50s. THe initial moisture plume as shown by GOES16 has now
shifted farther east of Indiana and the rest of the afternoon should
be spent within the warm and somewhat dry sector. Radar mosaics show
convection developing upstream in two areas. Severe storms were
developing over N MO and IA, and also over Arkansas and MO. The
storms over Arkansas and MO will be the storms of concern for
Central Indiana tonight. Water vapor imagery shows negatively tilted
upper low over NB. This low was providing diffluent flow aloft over
the Mississippi Valley where storm development was currently ongoing.
Tonight...
ACARS soundings this afternoon at IND show an inversion remaining in
place within the lower levels. This will keep convective development
from progressing over the next 2-3 hours. However as some clearing
and drier air arrives from the west, heating may allow this
inversion to weaken, allowing a more unstable column aloft to allow
convection. Showers developing over southern IL may be the trigger
for this, and thus we will need to continue some chc pops through
the afternoon and early evening.ight and people should be prepared
to activate their severe weather preparedness plan.
As the squall line exits overnight, some clearing is expected within
the dry slot as forecast soundings show a quickly drying column
overnight as cold air advection begins. Thus will trend toward
decreasing cloudiness overnight, however strong dynamics will remain
present aloft. Furthermore the strong pressure gradient across the
area will allow for the continued wind gusts of 30-40 mph. Thus the
wind advisory will be in effect at that point. We will expect lows
mainly in the lower 40s.
Saturday...
Models continue to suggest strong dynamics will still be pushing
across the Great Lakes on Saturday as an associated upper trough
axis is dragged across Central Indiana. Strong winds will persist
across the area on Saturday as a LLJ of near 50 knots will remain
aloft ahead of the trough axis. Forecast soundings show initially a
dry column in the wake of the cold front. However as convective
temperatures in the mid 40s are reached, forecast soundings show
lower level saturation amid cyclonic flow in place across the
region. This is indicative for convective showers. Thus will include
chance pops by late morning and afternoon. The wind advisory will
remain in place, as the ongoing strong pressure gradient will remain
in place, but will gradually diminish by late afternoon as the low
departs northeast and the gradient weakens. Expect only minimal
temperature rises to highs in the middle 40s as cold air advection,
and showers will remain in play for the afternoon.
&&
.Long Term...(Saturday night through Friday)
Issued at 305 PM EDT Fri Mar 31 2023
* Temperatures well above normal at times, particularly Monday-
Wednesday
* Showers and thunderstorms at times early to mid week, with severe
weather possible Tuesday afternoon - Tuesday night.
The long term period will begin with fast quasi-zonal flow across
the country, with temperatures fairly close to seasonal normals late
in the weekend. At the surface, high pressure traversing the region
Saturday night into Sunday evening will keep the area dry during
this period with ample sunshine Sunday.
As early as late Sunday night, shower chances will be required as
low amplitude disturbances move through the aforementioned fast flow
aloft, along with modest moisture return ahead of a low level
baroclinic zone.
This frontal zone will persist somewhere in the region as the upper
level flow amplifies early in the week, and broad
southerly/southwesterly flow and attendant increasing warmth and
moisture return through the low to mid levels of the troposphere
will allow for continued chances for showers and thunderstorms, with
PoPs increasing significantly Monday night into Tuesday.
Tuesday into Tuesday night, an extremely strong low pressure system
is likely to develop over the central High Plains into the upper
Midwest in response to the aforementioned amplifying flow aloft.
Strong dynamics and good moisture return as the Gulf remains wide
open appear likely to produce a regional severe weather event in the
region well outlined by SPC in the day 4-8 outlook - with the
highest threat at this time looking to be to our west over the lower
Missouri Valley and mid Mississippi Valley Tuesday afternoon. Late
Tuesday into Tuesday night, a severe weather threat is definitely in
the cards across central Indiana. Ample instability and extremely
strong low and deep layer shear values again appear likely across a
broad area in the open warm sector of the low. Pattern recognition
suggests this would most likely take the form for central Indiana of
one or more line segments with all hazards on the table, but cannot
completely rule out any convective mode, depending on degree and
timing of destabilization in the warm sector and other mesoscale
details that are too far out in time to resolve at this point.
Precip/storm threat should come to an end at least briefly Thursday
into Thursday evening as the cold front associated with the strong
low sweeps across the area. Shower chances may return very late in
the period, but are far more uncertain owing to growing model
differences.
&&
.Aviation...(00Z TAF Issuance)
Issued at 646 PM EDT Fri Mar 31 2023
Impacts:
-Southerly wind gusts to 40kts through the TAF period, brief
westerly gusts in excess of 50kts during line of storms.
-MVFR cigs to briefly IFR cigs this evening
-Line of storms expected from 02Z to 05Z, IFR vsbys during rain.
-LLWS through the TAF period.
Discussion:
A line of storms is expected to impact the terminals between 02Z and
05Z with the potential for wind gusts in excess of 50kts. Gradient
winds outside of storms will gust to around 40kts at times,
especially after 05Z. Vsbys will remain VFR outside of the heavier
rain. Cigs will remain MVFR through 05Z with low VFR conditions
afterwards. LLWS will be a concern with a very strong LLJ even with
surface gusts to 40kts. Winds will then gradually become more
westerly and eventually northwesterly tomorrow afternoon.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM EDT Saturday for INZ021-028>031-035>049-
051>057-060>065-067>072.
&&
$$
Mesoscale...BRB
Short Term...Puma
Long Term...Nield
Aviation...White
...UPDATED AVIATION FORECAST DISCUSSION...
.SYNOPSIS...
Issued at 345 PM CDT Fri Mar 31 2023
Key Messages:
-A powerful storm system will track across western Nebraska late
Monday, continuing through Tuesday into Tuesday night.
-Confidence is increasing in a multi-hazard storm with significant
snowfall accumulations and strong winds. The combination of heavy
snowfall and strong winds could result in blizzard conditions
across parts of western Nebraska.
-Widespread hazardous travel conditions and disruptions are
expected, including snow covered roads and reduced visibility,
particularly late Monday through early Wednesday.
-In the wake of the storm system, much below normal temperatures
and wind chill readings near or below zero are likely,
potentially creating a dangerous situation for livestock or those
who may become stranded due to the heavy snow and strong winds.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 345 PM CDT Fri Mar 31 2023
The models are maintaining Black Hills convergence snow into the
evening for a few hours. So the snow, albeit light, can continue in
that region this evening.
The nrn Plains storm will continue to track east through the upper
Missouri river basin this evening and be located across srn WI and
the upper Great Lakes by 12z Saturday morning. The short term model
blend plus the HRRR, RAP and HREF extends snow chances past midnight
across ncntl Nebraska so the Winter Weather Advisory has been
extended until 5 am CDT in that area. The new advisory will include
Holt County. The Winter Storm Warning can continue in place. There
is a very modest increase in snowfall amounts. Accumulations of up
to 8 inches are in place along the SD border and radar suggests
fingers of wrap-around snow are trying to develop.
A 90-10 percentile blend of the NBM was the basis for 25 to 35 mph
winds this evening with the strongest across ncntl Nebraska. This
might be too aggressive given the 500m AGL winds suggest 20 to 30 mph
surface winds. Gusts are capped at 55 mph, strongest across the
ncntl Nebraska area. Wind speeds will relax after midnight and by
Saturday morning, the models show clear skies and 1020mb high
pressure centered over cntl SD, Wrn Neb and wrn KS. The temperature
forecast tonight leans on a 25-50 percentile blend of the NBM for
lows in the teens and 20s. The NBM fingers the coldest temps over
Sheridan county and this is certainly warranted given the fresh snow
cover.
The same forecast strategy is in place Saturday for highs in the 50s
and 60s. The RAP model shows a fairly strong warm front migrating
east through wrn Nebraska. By late afternoon h850mb temperatures
should warm to 10C or warmer. Generally clear skies are in place. A
30-50kt low level jet develops Saturday night supporting continued
warm air advection followed by a weak Pacific cold front passage
toward morning.
.LONG TERM...(Sunday through Friday)
Issued at 345 PM CDT Fri Mar 31 2023
A storm system along the northern coast of British Columbia
is of particular interest today. The models continue to converge
on a likely storm track through WY Monday and then through wrn
Nebraska and SD Tuesday. In fact, the experimental Prob Winter
Storm product from WPC indicates likely winter storm impacts
across nwrn Nebraska- certainly warranted given the tight 100 mile
wide storm track cluster shown by the GFS, GEM and the ECM models
Tuesday.
Sfc pressure in the models for the storm continues in the range of
977mb - 986mb with the ECM the deepest. The ensemble means have
dropped to around 987mb and this indicates model convergence. High
winds are likely across parts of wrn and ncntl Nebraska late
Tuesday into Wednesday. The wind forecast gets a boost from the
NBM 90th percentile for 25 to 30 mph sustained speeds with gusts
to 45 mph. This is modest given the sub 990mb sfc pressure.
The NAM is in range of this storm and shows a band of FGEN snow
across nrn Neb and srn SD developing Sunday night and lasting
throughout the day Monday. The FGEN is very strong in the model and
the easterlies are moist. POPs are in place for this band but appear
to be underdone. Later forecasts may ramp this snow chance up.
This storm will pull down 1030mb sfc high pressure from Canada as it
crosses the Great Plains Tuesday and moves into the Great Lakes
Wednesday. The cold air will move south, mostly unmodified, across
the snow covered Dakotas and upper Midwest. The result, record low
temperatures and record low-high temperature are a distinct
possibility across northern Nebraska. Highs 10 to 30 degrees below
normal are in place Tuesday through Friday with the coldest
temperatures Tuesday and Wednesday. The predicted highs in the 20s
and lows in the single digits Tuesday and Wednesday are close to
record low temperatures and record low-highs at Valentine.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 626 PM CDT Fri Mar 31 2023
IFR/LIFR CIGs and visibilities will continue for northern
Nebraska terminals through this evening, with MVFR/low end VFR
further south and west. Stratus will exit the area overnight with
a return to VFR conditions by early Saturday morning continuing
through the end of the period.
Strong northwest winds persist across the area with gusts in
excess of 40kt at times. Winds weaken overnight and become
westerly for Saturday.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 1 AM CDT /midnight MDT/ Saturday for
NEZ004>006-094.
Winter Weather Advisory until 5 AM CDT Saturday for NEZ007>010.
&&
$$
SYNOPSIS...CDC
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Viken
Area Forecast Discussion
National Weather Service Louisville KY
1200 AM EDT Sat Apr 1 2023
.Mesoscale Update...
Issued at 1200 AM EDT Sat Apr 1 2023
Two convective clusters, one along the Ohio River within our CWA and
another farther south stretching from Hopkinsville into west TN
appear to be in the process of growing upscale into a larger quasi-
linear system as new convection has started within the last half
hour over Ohio and Muhlenberg County in between the two lines.
Environmental shear remains strong ahead of the current convection;
however, the instability will become less conducive for severe
storms (according to mesoanalysis CAPE fields and sfc obs) as storms
approach the I-65 corridor. Appears that while tornado threat will
still continue in the immediate near term, it is decreasing at this
hour in favor of a damaging wind threat.
Latest watch update has included Henry and Shelby County to account
for severe threat translating eastward.
Issued at 1005 PM EDT Fri Mar 31 2023
Recent radar trends to the west of our region suggest that
convective mode is currently transitioning from a more discrete mode
to a predominantly quasi-linear one. The first cluster of storms
which looks to impact our area stretches from just north of Paducah
to around Evansville, and looks to reach Dubois/Perry County just
after 1030 PM EDT. VAD wind profiles from VWX show very large low-
level helicity values (500+ m2/s2 0-1 km SRH), so from a dynamics
perspective, this cluster of storms is moving into a favorable
environment. Now that we`ve lost diurnal heating, any
destabilization ahead of ongoing convection will have to be done by
low-level theta-E advection and encroaching reduced heights aloft.
Compared to latest RAP mesoanalysis, convection to our west may be
slightly outrunning the best instability, but with the amount of
dynamic support that we`ve got, still expect storms to maintain
strength over the next few hours.
The main area of concern over the next 1-2 hours looks to be a
corridor from extreme northern Ohio County KY north to southern
Dubois County IN eastward to the I-65 corridor (mainly along and
north of the Ohio River). This area has been keyed on by Warn on
Forecast simulations consistently over the past 1-2 hours.
Issued at 830 PM EDT Fri Mar 31 2023
As was mentioned in the previous update concerning the watch
potential over the CWA, Tornado Watch 98 has been issued for all of
our southern IN counties along with western and central KY until 3am
EDT/2am CDT. Very strong 60-70kt LLJ will work over the Ohio Valley
now through 07z. This along with the approaching 80-100kt mid-level
jet will increase the deep layer shear over the Ohio Valley and
increasing the potential development of severe weather out ahead of
the approaching cold front. Latest 2330z update of the WoF continues
to show this split dynamic over western/central KY with a favorable
low-level updraft helicity track coming the current storms over the
Boot Heel of MO and extending it northwestward along the Ohio River
and reaching Hancock Co. KY/Perry Co. IN between 03/04z as it shows
the cells currently over western TN weakening as they approach or
southwestern CWA.
Hi-res model soundings continue show a ramp up of instability and
shears after 02/03z across the CWA. The threat remains strong
damaging winds and spin up tornadoes.
Issued at 720 PM EDT Fri Mar 31 2023
Current Radar imagery from KLVX WSR-88D has a broad area of
stratiform thundershowers moving over Butler, Logan, Simpson and
Warren counties as it continues to move eastward. Satellite imagery
generally shows Broken to overcast cloud cover over most of western
KY with a few breaks in the clouds over Evansville IN. The main show
continues to be in the warm sector just behind the warm front that
stretches from around Davenport IA to Evansville, IN to around
Nashville, TN while the cold front stretches from about Cedar Rapids
IA southward through central MO into eastern TX. Activity currently
stretching from near St. Louis across south central MO into central
AR is where our focus is for what is expected to push through
western KY into central KY and southern IN later tonight.
Cloud cover and slightly cooler temperatures have helped keep
instability levels down but per the KY Mesonet, we have dew points
in the low/mid 60s and temperatures in the upper 60s/near 70. This
still remains the focus for the highest risk of severe weather later
this evening with a gradual diminishing of that severe threat as it
works eastward into central KY. WoFs or Warn on Forecast guidance
this evening has been doing an extremely good job on placement and
severity of activity through the afternoon and early evening. If
this trend continues, the WoF brings the current storm just
northeast of Memphis to just south of BWG by around 0130z but with a
much lower severe threat. This is likely due to the aforementioned
stratiform thundershowers taking place across the area as of the
writing of this update.
Also been noticing a trend in recent CAM updates of a north/south
split in the main line of activity as it works across
western/central KY later this evening. General timing looks good
with the strongest activity working into our western southern IN
counties by around 02-03z then to the I-65 corridor between 03-04z
then into the Bluegrass, including Lexington between 04z-06z. Given
the model soundings showing good shear and SRH values ahead of the
boundary this evening the pervasive thought in the office is we
could still see a watch issued at some point later this evening.
&&
.Short Term...(Today and tonight)
Issued at 330 PM EDT Fri Mar 31 2023
Satellite imagery still shows the majority of the region remains
under cloudy skies. A few holes are allowing some sunshine to reach
the ground through the CWA, but the cloud cover is keeping most of
our temperatures near the mid 50s which is below what was forecast
earlier. Western Kentucky and southwest Indiana are seeing
temperatures in the 60s to almost 70. Southern winds ahead of the
approaching cold front will continue to lift temperatures and dew
points. Dew points are currently in the 50s and are expected to
climb into the upper 50s to low 60s ahead of an advancing cold
front. A lot of the precipitation in the CWA has drifted off to the
east, but scattered showers remain across our southern counties with
isolated pockets to the north. A few rumbles of thunder continue,
but precipitation through the afternoon hours is expected to remain
elevated.
Tonight, the aforementioned cold front moving east towards southern
Indiana and central Kentucky continues to be the focus of concern.
The CAMs have fairly good agreement in timing and general overall
environmental parameters. Strong wind shear will be the driving
force that will make severe weather possible. Most models have the
low level jet around 70 to 75 knots. Hodographs show large areas of
low level wind shear. Bulk shear values between 0-6 km will likely
be in the 60-80 knot range, which can easily support severe weather.
Storm relative helicity between the 0-1 km level could see values in
the 500-600+ m2/s2 range, so even with the mediocre low level lapse
rates, shear values this strong can overcome near surface stability.
MLCAPE values remain fairly high for a cool season system. Values
could range from a couple hundred J/kg to 500 or 600. So with this
environment, the main threats will be gusty winds and possible
tornadoes. The threat of severe weather will be the higher to the
west and diminish as the system moves east. Believe the threat will
noticeably drop off east of Interstate 65.
Behind the front, the threat of severe weather will be over. Skies
will clear as surface high pressure begins moving into the region.
Gradient winds will remain gusty for the rest of the night.
Southwest winds around 10-20 mph with gust to near 30 mph before
winds begin increasing again on Saturday. Gusts on Saturday are
expected to reach into advisory levels with gusts over 40 mph
because of this and windy conditions today, the wind advisory
already in place will remain from 8 PM this evening until 5 PM
Saturday.
&&
.Long Term...(Sunday through Friday)
Issued at 209 PM EDT Fri Mar 31 2023
Winds will begin to taper down Saturday night as the pressure
gradient relaxes and nocturnal inversion sets in. High pressure is
expected to settle over the region by Sunday morning, so winds will
likely go light to calm by then. The surface high will push toward
the Appalachians during the day Sunday, and southerly return flow
will pick up across southern Indiana and central Kentucky. With
sunny skies and light southerly winds, highs should top out in the
upper 50s to low 60s.
Upper level flow becomes amplified going into early next week as a
trough moves into the western CONUS and ridging develops in the
eastern CONUS. A surface warm front will lift from the Gulf Coast
states into the Ohio Valley during this time, engulfing us well
within the warm sector ahead of a developing low pressure system and
surface cold front. Models still vary on the timing of various
perturbations within the flow of the trough and the passage of the
cold front, but the Tuesday - Wednesday timeframe could feature
periodic active weather given the co-location of favorable
thermodynamics and kinematics for strong/severe thunderstorms.
The front will likely push through the region by Thursday with
surface high pressure building in behind it, though some ensembles
suggest the frontal passage could be delayed or even held up, so
have included low-chance PoPs through the end of the week.
&&
.Aviation...(06Z TAF Issuance)
Issued at 650 PM EDT Fri Mar 31 2023
Period of poor flying conditions upcoming, as we deal with both
strong winds, low-level wind shear, and storms. The latter will be
in play later through the evening hours. Winds aloft will pick up
this evening as a potent low-pressure system spins across the Great
Lakes. Expect a band of heavier thunderstorms with possible 50+ kt
winds, though TAFs are a little more conservative, to move through
the sites from west to east this evening before our rain chances
drop off quickly. Low-level wind shear will become more westerly
after ~6Z before surface wind gusts pick up at all terminals
Saturday morning. What may help mitigate some stronger wind gusts
later Saturday morning and afternoon is a cloud deck in the 3-4 kft
range that will drop in from the northeast ahead of another quick-
moving disturbance.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Wind Advisory until 5 PM EDT /4 PM CDT/ Saturday for KYZ023>043-
045>049-053>057-061>067-070>078-081-082.
IN...Wind Advisory until 5 PM EDT /4 PM CDT/ Saturday for INZ076>079-
083-084-089>092.
&&
$$
Mesoscale...CSG
Short Term...KDW
Long Term...DM
Aviation...RJS
Area Forecast Discussion
National Weather Service Marquette MI
1018 PM EDT Fri Mar 31 2023
.UPDATE...
Issued at 1017 PM EDT FRI MAR 31 2023
Impressive looking mid-level low is moving e into IA this evening.
While strong/svr storms are rolling into the southern Great Lakes,
pcpn shield to the n and ne of the mid-level low has rapidly
developed and consolidated across WI this evening under strong
forcing. GOES 16 GLM and lightning detection network has shown
thunder reaching as far n as Menominee County this evening. Obs in
far northern WI are mostly VFR vis so, ptype is mostly something
other than snow at the moment.
Radar trends are suggestive that what will become a hvy snow band on
the n side of system may have a more difficult time spreading as far
n as previously anticipated. Most of the model trends since 12z
today and in particular the hourly HRRR/RAP runs support that idea.
00Z HRRR has no measurable pcpn generally n of an Ironwood to
Marquette to Whitefish Pt line tonight. QFP gradient is tight,
ranging up to 1-1.5 inches across s central Upper MI, but models all
along have indicated such a gradient of QPF. In fcst updates so far
thru the evening, have shaved back the northern end of the QPF. Next
update will continue that trend of cutting back QPF and thus snow
amounts on the n side of the pcpn shield, though a sharp gradient to
much higher amounts southward will still be present. Expect
wet/dense snow accumulations over a foot where the heavy snow
band cuts across the s central to eastern fcst area. Will leave
headlines as is since snow accumulations will likely still warrant
a headline in southern portions of the counties that have a sharp
n to s snow accumulation gradient, though Ontonagon/southern
Houghton/Baraga counties are certainly questionable to remain in
an advy.
&&
.SHORT TERM...(Through Tonight)
Issued at 328 PM EDT FRI MAR 31 2023
Our brief break in active weather continues this afternoon, with
just some stray rain/snow shower activity and patchy fog/mist. This
will quickly come to an end into the evening, when the next wave of
wintry precipitation arrives.
At present, water vapor imagery shows an impressive mid/upper level
circulation over Nebraska and South Dakota. Surface observations
indicate the surface low to be over IA, with a frontal boundary
extending northeastward through southern WI and into Lower Michigan.
Thus, this system should stay fairly progressive, quickly expected
to track northeast into central WI by this evening and into the
northern or central LP by early Saturday morning. Strong isentropic
ascent as the warm front lifts northward through WI and the LP
should see more widespread wintry precipitation developing from
southwest to northeast from 00Z onwards. Simulated reflectivity
continues to indicate a tight deformation band developing around
06Z, finally diminishing and pivoting out of the area around 12-15Z.
The exact placement of the band remains in question, though latest
trends have placed it slightly more southeast compared to previous
forecast cycles. We are looking at our highest QPF to fall somewhere
in a swath from an Iron Mountain to Newberry line, southeast towards
the Lake Michigan shoreline.
As for precipitation type: Model soundings in the western UP remain
cool enough for precipitation to come in as snow for most of the
next round, though a warm nose approaching the 0C line indicates a
potential for some sleet to mix in at the onset before a rapid
change over to snow. Heading eastward through the UP, milder
temperatures are present aloft at onset. This would indicate a
better chance for a wintry mix with sleet and freezing rain, and
potentially all rain in Menominee county to start. By 06Z, though,
we should be cold enough for a change entirely over to snow area-
wide. NBM, HREF, and much of the hi-res guidance continues to show a
good chance of snowfall rates anywhere from 1-3in/hr for a good 6
hours from around 06-12Z Saturday where the band does set up, which
could easily lead to localized totals as high as a foot. The
gradient will be very tight, though, with significant "bust"
potential if the placement of the band shifts compared to the
current forecast. In the western UP, meanwhile, snow/ice totals will
be significantly lighter, with much of the westernmost UP counties
struggling to reach advisory criteria and Keweenaw county
potentially missing out on any snow accumulations at all.
The other concern, meanwhile, will be gusty northeast winds. A
strong pressure gradient develops overnight as the surface low makes
its closest approach, leading to increasing wind speeds at the
surface which would be strongest along the Superior shoreline and in
northeast upslope-favored locations. With robust 40 to 50 knot flow
present just off the surface, strong wind gusts could easily mix
down to the surface. This would lead to a risk not only for more
power outages as strong winds bring down snow-laden tree branches
and power lines, but there is also a concern for some lakeshore
flooding closer to Superior with persistent, gusty onshore flow.
.LONG TERM...(Saturday through Friday)
Issued at 249 PM EDT FRI MAR 31 2023
GEFS 500mb height spaghetti plot illustrates good agreement among
the various ensemble members of the coming pattern into next week.
Of course, there`s still some uncertainties when you narrow things
down to sensible weather, but overall, it appears the active pattern
across the Upper Great Lakes will continue into next week.
Beginning Saturday morning, ongoing vigorous spring storm will
continue to impact our region. At 12z, the nearly occluded system`s
center is expected be centered near the Door Peninsula. There`s some
subtle differences among the various guidance packages about how far
west, east, south, or north of the Door the low will be, so there
are some differences in how far west and north the outgoing band of
heavy snow will be. At the moment, confidence is highest that the
east will continue to see accumulating snow Saturday morning given
the track of the system`s deformation zone. The 0z and 12z HREF
paint a swath of 60-90+% probabilities of 1-2" per hour rates from
north-central Menominee County all the way to the Sault Ste Marie
through at least 10-11am local time. Quick improvement is expected
as the system shifts eastward and the deformation zone follows. By
1pm, all snow is expecting to be east of our forecast area.
With the system exiting and the pressure gradient relaxing as high
pressure slides from the Dakotas into the Upper Great Lakes, winds
across the region should also relax through the day. However,
there`s good agreement among the deterministic suite that pressure
rises near 15-17mb per 6 hours can be expected behind the system.
With the colder airmass overhead, stronger winds out of the north
and northeast will continue to be possible. Steeper low level lapse
rates will make mixing into the 30-40mph winds aloft possible,
particularly in the east half and by Lake Superior in the morning
and early afternoon hours. While these are expected to improve
through the afternoon, 20-30 mph winds can`t be ruled out into the
late afternoon/early evening in the east. With the winds improving
over Lake Superior as well, wave heights should also begin to come
down, resulting in a decreasing threat for lakeshore flooding or
beach erosion through the day.
Skies should clear from west to east through the day Saturday; these
clearer skies should stick around Saturday evening. I expect us to
decouple thanks to the recent snowfall and the airmass being dry.
This should support some radiational cooling and allow overnight
lows to dip into the single digits in the interior and teens by the
lakeshores. Some high and mid-level cloud cover begins inching its
way back into the west on the nose of a LLJ and WAA aloft by early
morning. As the sun rises Sunday, we should be able to mix into the
LLJ. Model soundings suggests widespread 20-30 mph wind gusts from
the south will be possible Sunday with some areas potentially 30-
40mph. The warmer airmass building in will allow temps to climb into
the low 40s or near 40F for most of the region.
The LLJ will precede a clipper system moving through or near the
north end of Lake Superior Sunday night. Isentropically forced
precip may accompany this over the west or northern portions of the
CWA. A majority of guidance suggests snow to be the most likely
ptype, but NBM unconditional ptypes does suggest a mix of rain or
snow will be possible. Overall though, QPF amounts of 0.10-0.2
inches or less and low snow ratios should yield 1-2 inches of wet
snow if so. The clipper`s cold front will swing through from west to
east Monday and could support another round of light precip.
The next item of interest looks to be in the Tuesday night through
Wednesday night time frame. There`s good model agreement that
another vigorous system will eject out of the northern/central
Plains and lift into Ontario. Much like any system following this
trajectory at this time of year, where the low tracks will largely
determine whether we see snow or rain. 0z and 12z EPS, GEPS, and
GEFS MSLP ensemble mean and low clusterings appear in decent
agreement that the low is more likely to lift into the Arrowhead and
then into Lake Superior Wednesday, suggesting snow could precede
rain or a sloppy wintry mix during the event initially before a
transition back to snow on the low`s western flank. It also suggests
the potential for a dry slot to really cut into QPF amounts. Much
like tonight`s system though, ptype is tricky because so much
depends on the exact track of the system, degree and timing of air
temp changes aloft, and forcing mechanism and magnitudes. While my
overall confidence is currently low-medium (25-50%) for this event,
the 0z ECMWF EFI shows that some ensemble members include an
unusually high amount of QPF and near extreme winds when compared
against a 30 year climate analysis. The SoT values between 1 and 2
on Lake Superior and less than 1 over Upper Michigan, suggests that
these events aren`t unheard of for this time of year though. While
this doesn`t increase my confidence much, it does make the gales and
storm force winds for Lake Superior, land winds near 30-40mph, and
influence of Gulf of Mexico moisture in some of the deterministic
guidance packages believable though. At this point, it`s best to
continue monitoring forecasts for updates regarding this system.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 758 PM EDT FRI MAR 31 2023
Low pres over ne IA will track ene overnight and Fri, bringing
strong/gusty ne winds and snow into Upper MI. Expect winds at
IWD/CMX/SAW to gust to 30-40kt tonight into Sat morning, strongest
at SAW. IWD will be on the nw side of the snow shield. MVFR cigs at
IWD should fall back to IFR this evening with MVFR vis in -sn. The
-sn will end overnight, and as much drier air arrives, clouds will
clear out to VFR by late morning, if not sooner. The snow will
likely remain s and se of CMX tonight. VFR currently at CMX will
give way to MVFR cigs this evening with these clouds then clearing
out to VFR Sat morning. SAW will be most impacted by the snow
associated with the low pres. Current LIFR cigs will remain in place
as -sn/IFR vis set in the next couple of hrs. Expect a period of +sn
overnight with conditions likely falling blo airfield landing mins
in +sn/considerable blsn. Although snow quickly diminishes/ends
early Fri morning, blsn will likely continue to reduce vis for
several hrs. Expect conditions to improve to VFR by mid aftn.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 249 PM EDT FRI MAR 31 2023
...Strong Gale and Heavy Freezing Spray expected into Saturday...
...Low end gale possible Sunday afternoon and evening...
Northeasterly winds have increased today, with western Lake Superior
observations seeing Gale conditions. As the day continues and the
pressure gradient increases ahead of a vigorous spring system
moving into the Upper Great Lakes, these stronger winds will
continue increasing and spreading east across the entire lake.
Widespread gales near 40-45kts are expected. NBM wind probabilities
and internal probabilistic tools suggest north and west-central Lake
Superior would be the most likely spots to experience Storm Force
winds, but it can`t be ruled out completely in the east. Strongest
winds are expected between sunset and sunrise tonight, with slow
improvement from west to east beginning early Saturday morning. The
east is likely to continue seeing Gale conditions into early
Saturday afternoon. These strong winds will also build waves upwards
of 15 to 20 feet, particularly along the southern half of Lake
Superior. Additionally, the winds coupled with the incoming cold air
will also support conditions ripe for heavy ice accretion rates
overnight.
Winds relax below 20kts Saturday night, but increase again Sunday
ahead of a clipper system pressing east through Lake Superior.
Guidance suggests a strong 30-40kt LLJ will move over Lake Superior
through the day. Because the lake is ice free, the modest warm air
advection should still result in some winds mixing to the surface. I
would expect near 30kt winds, mainly in eastern Lake Superior, but
some low end gales can`t be ruled out, particularly Sunday
afternoon/evening for higher reporting platforms.
Another system strong system looks to move into the Upper Great
Lakes by the middle of next week. While there`s still a good bit of
uncertainty surrounding this system, confidence is currently medium-
high (50-75%) that at least gales will occur on Lake Superior
Tuesday night and Wednesday. Confidence in storms is also around
25%.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Lakeshore Flood Advisory from 2 AM to 2 PM EDT Saturday for
MIZ001>007.
Winter Weather Advisory until 8 AM EDT /7 AM CDT/ Saturday for
MIZ002-004-009-084.
Winter Storm Warning until 2 PM EDT Saturday for MIZ005-006.
Winter Storm Warning from 2 AM EDT /1 AM CDT/ to 2 PM EDT /1 PM
CDT/ Saturday for MIZ007-012>014-085.
Winter Storm Warning until 7 AM CDT Saturday for MIZ010-011.
Lake Superior...
Gale Warning until 2 PM EDT /1 PM CDT/ Saturday for LSZ162-
240>244-263-264.
Heavy Freezing Spray Warning from 2 AM EDT /1 AM CDT/ to 1 PM
EDT /noon CDT/ Saturday for LSZ162-243>248-263>267.
Gale Warning until 5 PM EDT Saturday for LSZ245>251-265>267.
Lake Michigan...
Gale Warning until 5 PM EDT Saturday for LMZ221-248-250.
&&
$$
UPDATE...Rolfson
SHORT TERM...LC
LONG TERM...JTP
AVIATION...Rolfson
MARINE...JTP
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
929 PM EDT Fri Mar 31 2023
...New UPDATE...
.UPDATE...
Issued at 903 PM EDT Fri Mar 31 2023
Key Messages:
1. A nearly solid line of showers and storms, mainly between 3 and
6 am. Main threat will be damaging winds.
2. Isolated tornadoes mainly across the Plateau and southeast
Tennessee. Tornado potential is a conditional threat depending on
low-level instability and mixing becoming surface based.
3. Pressure gradient induced high winds, especially across the far
east Tennessee mountains and foothills.
Discussion:
Currently, a warm front extends from middle Tennessee into
northern Alabama and far western Georgia. How far northeast this
boundary can be pulled northeast into east Tennessee will play a
large role in determining tornado potential across the Plateau and
southeast Tennessee. Latest HRRR model trends does suggest this
boundary will be able to pull northeast with 0-3km CAPES of 40+
and mixing becoming surface based.
The strong upper level dynamics is depicted by latest
deterministic models and ensembles to increase over the region by
09Z producing strong upper divergence. Large scale forcing will
enhance the fronto-genetic forcing allowing the current scattered
storm coverage to become a nearly solid line.
Due to the strong low-level jet of 65-70kts (850mb), this line
will have the potential of producing localized damaging winds,
especially across the Plateau and southern half of the Tennessee
valley.
Since the low-level jet is not mixing to the surface (except ridge
tops), have delayed the wind advisory for the central and southern
areas until 2 am. Otherwise, no changes to ongoing wind
warning/advisories. So far, Cove Mountain has reported a gusts up
to 70 mph and Camp Creek near 50 mph.
Have a good night and stay safe.
&&
.SHORT TERM...
(This evening through Saturday)
Issued at 259 PM EDT Fri Mar 31 2023
Key Messages:
1. A band of showers and storms will move through tonight and some
storms may be strong to severe, especially along the Cumberland
Plateau and into the Southern Valley.
2. The main threat with the strong to severe storms will be damaging
winds, but a brief tornado is possible as well.
3. Strong and gusty winds are expected at times, with the highest
winds over the TN mountains.
Discussion:
A powerful low pressure system will track from the Plains across the
Great Lakes into the NE states by the end of the period. A
prefrontal trough will move through our area tonight, and while
there is some convection ahead of the main area it looks like the
main band of showers and thunderstorms will move in from the west
most likely after midnight. As has been advertised, the LLJ and deep-
layer/low-level shear will be very impressive with the main question
being how much convective energy will be available when the
convection moves through. This is also limited in our area both by
the time of day and less than ideal upper support. The latest HREF
continues to indicate values of 250+ J/kg will be most likely along
the Plateau and southern Valley areas with lower values further
east, although it is worth noting that values have trended up
slightly in some of the latest guidance. It still looks like the
main severe threat will damaging winds. However, there remains a
tornado threat especially across the Plateau and into the southern
valley. The HREF continues to highlight the highest probability of
helicity tracks in these areas, but a low threat does exist to the
east of these areas dependent on exactly how much convective energy
is available at the time. Any areas that see repeated heavy
downpours may see some localized flooding although that threat
appears significantly lower than the severe threat at this time.
Winds will continue to increase across the mountains and foothills
into tonight as the LLJ increases, and models indicate the
orientation of the jet to the mountains may become briefly more
favorable for some mountain wave enhancement mainly this
evening/early tonight. Outside of the mountains, winds will increase
tonight as well with the strongest winds likely to occur ahead of
and with the band of convection. Once the convective band moves
through there will likely be slight lull in the winds, however the
strong surface pressure gradient, WSW 850mb winds reaching 45-50kts
again, and expected deep mixing all indicate we will see windy
conditions across the entire area by late Saturday morning into the
afternoon. Will keep the wind advisories and warning as they are for
now except to delay the start of the first wind advisory until 03Z
tonight. The hi-res guidance suggests wind speeds may flirt with
warning criteria even in valley locations, so cannot rule out later
shifts needing to upgrade at least a portion of the wind advisory to
a warning.
Once any lingering convection in eastern portions of the area exits
early Saturday, we will see dry conditions and plenty of sunshine
along with the aforementioned winds. Temperatures will be quite warm
with highs in the 70s in most valley areas.
&&
.LONG TERM...
(Saturday night through next Friday)
Issued at 259 PM EDT Fri Mar 31 2023
Key Messages:
1. Below normal temperatures Saturday night/Sunday morning with
patchy frost possible on the Plateau and Appalachian Mountains.
2. Shower and thunderstorm chances return beginning Tuesday as a
cold front tries to move through the area.
Discussion:
Saturday night into Sunday will mark another chilly morning behind
the front as cold air from the northwest funnels into the region.
Temperatures will likely drop down into the 30`s for much of the
eastern TN valley, and possibly near or below freezing in the higher
elevations of the Cumberland Plateau and Appalachian Mountains. In
the Valley winds could calm down enough to see patchy frost with the
highest chance to see frost being on the Plateau, frost/freeze
products may be needed again.
Surface high pressure and weak mid level ridging will begin to build
in late in the weekend, which kick start a quick warm up into next
week. Temperatures are expected to climb into the lower 80`s by
Tuesday. A weak shortwave is expected to push through the southeast
to start off the work week. Still some discrepancies with the exact
location of this shortwave, but areas near or south of the TN/GA
state line have the highest chance to get a shower from this system.
A strengthening system will develop across the plains and try to
drag a cold front through the eastern US. With our area being in the
warm sector expect to see scattered showers and thunderstorms
develop on Tuesday and Wednesday. Some of the deterministic models
are indicating that the mid week could stall out somewhere along the
Tennessee Valley into the Mid Atlantic. Should this happen it would
likely act as a focusing mechanism for continuous rain chances for
the second half of the week and into the weekend, before finally
moving out late in the weekend. Still lots of uncertainty with the
location of the front this far out, but it will be worth keeping an
eye on as showers and storms are expected along the front for
several days next week.
&&
.AVIATION...
(00Z TAFS)
Issued at 702 PM EDT Fri Mar 31 2023
Conditions will deteroiate quickly across the TAF sites between
07-10Z when a squall line of storms moves across the region.
Damaging winds are possible with the greatest threat at CHA and
TYS. Otherwise, main concern through the TAF period will be
tightening pressure gradients producing windy conditions
especially for Saturday. Wind gusts in excess of 40kts is possible
at TRI and TYS.
Generally VFR ceilings until the storms moves through but quickly
returns by 12Z as drier air moves back into the area.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 61 78 42 69 / 90 10 0 0
Knoxville McGhee Tyson Airport, TN 59 74 38 65 / 90 20 0 0
Oak Ridge, TN 58 75 37 65 / 100 10 0 0
Tri Cities Airport, TN 53 72 37 61 / 90 40 0 0
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...Wind Advisory from 2 AM to 8 PM EDT Saturday for Cherokee-Clay.
TN...Wind Advisory from 2 AM EDT /1 AM CDT/ to 8 PM EDT /7 PM CDT/
Saturday for Anderson-Bledsoe-Bradley-Campbell-East Polk-
Hamilton-Knox-Loudon-Marion-McMinn-Meigs-Morgan-North
Sevier-Northwest Blount-Northwest Monroe-Rhea-Roane-Scott
TN-Sequatchie-Union-West Polk.
Wind Advisory from 8 AM to 8 PM EDT Saturday for Claiborne-
Grainger-Hamblen-Hancock-Hawkins-Jefferson-Northwest Carter-
Northwest Cocke-Northwest Greene-Sullivan-Washington TN.
High Wind Warning until 11 PM EDT Saturday for Blount Smoky
Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky
Mountains-Southeast Carter-Southeast Greene-Southeast
Monroe-Unicoi.
VA...Wind Advisory from 8 AM to 8 PM EDT Saturday for Lee-Russell-
Scott VA-Washington VA-Wise.
&&
$$
SHORT TERM...DH
AVIATION...DH
Area Forecast Discussion
National Weather Service Nashville TN
919 PM CDT Fri Mar 31 2023
...New UPDATE...
.UPDATE...
Issued at 918 PM CDT Fri Mar 31 2023
Convection trying to organize across western TN at this time.
Primary cold front is still back in central AR with impressive
dewpoint gradients noted. Pre frontal forcing over wester TN is
still expected to strengthen some although instability levels drop
toward the east. helicity and shear is still quite notable with 0-
500M helicity values of 400 M(2) S(-2) along and just east of the
developing pre frontal dynamics. Strongest storm right now is
located about 40 miles west of Wayne county.
For the forecast, wont change anything at this point. Hrrr still
brings the strongest storm potential to the I-65 corridor between
1pm and 1am. The tornado watch still remains and the situation will
continue to be monitored going forward. Best tornadic threat will be
across the western quarter where the moderate risk still resides.
Damaging straight line winds may end up being the primary threat
with perhaps some hail for our western counties
&&
.SHORT TERM...
(This afternoon through Saturday Night)
Issued at 124 PM CDT Fri Mar 31 2023
Bottom Line:
Severe thunderstorms are expected this evening and overnight with
damaging straight-line winds of 60-75 mph the primary threat
across all of Middle TN. Isolated tornadoes can`t be ruled out
mainly west of I-65. This is still expected to be an overnight
event with main timing between 9PM and 3AM. Have multiple,
reliable ways that will wake you up in order to receive warnings
should they be issued for your area.
Forecast Details:
Water vapor imagery this afternoon shows a potent upper-level low
over the northern Great Plains while latest obs indicate a deep
surface low over Iowa. Across our area, southerly surface winds
have been working to usher in favorable low-level moisture, and
this is evident on the observed soundings with notable improvement
from the 06Z, 12Z, to 18Z soundings. And while rain has been
impacting the area off-and-on all morning, we are starting to see
breaks in the clouds that should aid in destabilizing the
atmosphere. Wind shear, of course, remains very favorable for this
event. Mid-level flow will strengthen as the upper-level low
continues to approach, and the LLJ kicks in tonight with 850mb
wind speeds nearing or exceeding 70 knots by 03Z. Forecast
soundings show impressive 0-3km SRH anywhere between 400 and 700
m2/s2. But the main question remains how much instability will be
available, and even with this forecast package, models are in poor
agreement over this across our area. Aside from the numbers of
CAPE, there are some things they agree on. Highest instability
looks to be west of I-65, and in particular, in the quadrant south
of I-40. CAPE looks to fall of rapidly amongst all of the models
east of I-65. Thus, the messaging hasn`t really changed with this
forecast package. With plentiful shear, damaging winds will be
possible areawide with the greatest chance for isolated tornadoes
west of I-65 where instability will be greatest.
The other thing to make mention of is that some CAMs have been
waffling all day on whether or not there will be pre-frontal
storms this evening across the west before the main event.
Confidence is low, but if they do develop, they will be in an
environment that offers more instability although not as much
shear. Thus, won`t completely rule out an initial round of
isolated to scattered storms west of I-65 that could turn strong
to marginally severe. However, the main event is still expected
between that 9PM to 3AM window.
Finally, no changes were made to the Wind Advisory that begins
this evening. Southerly winds will strengthen ahead of our
convection and will stay strong post-frontal boundary. Gusts of 35
to 45 mph will be possible through Saturday afternoon. Those
stronger gusts may linger longer across the east through the early
evening hours Saturday. However, given the focus on tonight`s
event first, will let the next shift take a closer look on whether
or not an extension in time will be warranted for that Wind
Advisory.
Otherwise, temperatures cool on Saturday in the wake of the cold
front and low temperatures Saturday night and into Sunday morning
will be close to the freezing mark, making widespread frost
likely.
&&
.LONG TERM...
(Sunday through next Friday)
Issued at 124 PM CDT Fri Mar 31 2023
Sunday should be a gorgeous day for Middle TN with plenty of sun,
light winds, and temperatures in the mid to upper-60`s. As we head
into early next week, a more active pattern presents itself as
surface winds become southerly once again, and increasing moisture
leads to low PoPs. Models are still suggesting that additional
strong to severe thunderstorms are possible in the
Tuesday/Wednesday time frame with those details being ironed out
as we get closer. A wet pattern may even linger through the end of
next week as a stationary front parks itself to our south.
&&
.AVIATION...
(00Z TAFS)
Issued at 518 PM CDT Fri Mar 31 202
Cold front will sweep across the area late tonight. In advance of
this feature, severe thunderstorms will be possible. Damaging
straight line winds, isolated tornados with some large hail will
be possible. The timeframe for our taf sites for the strongest
storms looks like 03Z until 09Z.
Moving on, a second cold front will move through early Saturday
and provide additional clearing. It will be quite breezy once
again but sky conditions will quickly morph toward SKC.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 58 70 39 66 / 100 0 0 0
Clarksville 55 64 36 66 / 90 0 0 0
Crossville 55 68 33 63 / 90 10 0 0
Columbia 56 71 37 68 / 90 0 0 0
Cookeville 56 69 36 63 / 100 0 0 0
Jamestown 54 68 33 63 / 100 0 0 0
Lawrenceburg 57 72 37 68 / 90 0 0 0
Murfreesboro 56 72 36 67 / 90 0 0 0
Waverly 55 64 37 67 / 100 0 0 0
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 1 PM CDT Saturday for Bedford-Cannon-
Cheatham-Clay-Coffee-Cumberland-Davidson-De Kalb-Dickson-
Fentress-Giles-Grundy-Hickman-Houston-Humphreys-Jackson-Lawrence-
Lewis-Macon-Marshall-Maury-Montgomery-Overton-Perry-Pickett-
Putnam-Robertson-Rutherford-Smith-Stewart-Sumner-Trousdale-Van
Buren-Warren-Wayne-White-Williamson-Wilson.
&&
$$
UPDATE.......21
SHORT TERM...Clements
LONG TERM....Clements
AVIATION.....21
Area Forecast Discussion...UPDATED
National Weather Service Paducah KY
825 PM CDT Fri Mar 31 2023
.UPDATE...
Issued at 825 PM CDT Fri Mar 31 2023
Lone cluster of cells has worked through the eroding cap and is
moving quickly northeast across parts of southern Illinois.
LAPS/Mesoanalysis shows about 1000 J/kg of MLCAPE. VWP hodographs
show around 950 m2/s2 of 0-1km SRH, 50-60 kts of 0-1km total
shear. Meso has had a hard time organizing on the ongoing
supercell cluster but potential remains for this area or other
development to produce tornadoes with an organized straight line
wind potential also possibly developing if the current upscale
processes continue.
Surface dryline is approaching Carter/Ripley and may be able to
start trimming some of the watch from west to east in an hour or
so.
UPDATE Issued at 653 PM CDT Fri Mar 31 2023
LAPS/RAP soundings still show a weak subsidence inversion/cap in
place over the region. Cells to the northwest of the CWA are
left- moving which given the hodographs gives the appearance that
they may not be totally rooted in the deeper low level moisture.
Shear has started to relax just a bit over the last hour or so.
A favorable airmass is still in place for severe weather and
tornadoes, but we are starting to become more cautiously
optimistic drier/warmer air in the 700-800mb layer will limit
convective coverage. We can`t completely let the guard down, and
are in the process of coordinating a watch extension into SE
Illinois, SW Indiana and the rest of western Kentucky, but it will
be a conventional watch and not a "PDS" watch.
Also updated for 00z TAFs.
UPDATE Issued at 310 PM CDT Fri Mar 31 2023
Convection in northeastern Arkansas may be becoming more surface
based. Dewpoints are increasing into the mid to upper 60s in this
area although it may still outrun the best mixed-layer instability
as it moves eastward. A local extension of the tornado watch
further east, particularly over western Kentucky may be required
shortly depending on trends with this cluster.
&&
.SHORT TERM...(Tonight through Sunday night)
Issued at 148 PM CDT Fri Mar 31 2023
In the near term, convection moving into SEMO seems to be
slightly outrunning the best instability. Breaks in the overcast
are allowing heating to build as strong moisture advection occurs
from the southwest. A cluster of supercell storms is forming over
Central Arkansas and may prove to be the initial main threat for
the Paducah CWA. Also watching cu towers building in southwestern
Missouri along a front/dryline. LAPS sounding show a weak capping
inversion around 700mb. RAP soundings forecast that to erode
through the afternoon. Expecting a steady destabilization over
the next few hours ending up around 1500 J/kg of MLCAPE with
100-150 in the 0-3km level. Mid-level lapse rates are 7.5 to 8.0
degC/km which is stronger than originally anticipated. 0-1km SRH
on NQA/PAH VWP is running around 400 m2/s2. By the time any
southwestern MO developing convection arrives after dark the shear
may be slightly more unidirectional, but will still be strong.
In short we are quite concerned the cluster of supercell storms
in Arkansas will move into the region amid a highly favorable
environment for all modes of severe. Significant/longer-tracked
tornadoes are entirely possible. That threat will likely persist
through the early evening amid favorable shear and instability.
There is some thought the timing of the storms may limit
instability in the eastern part of our area (i.e.
Evansville/Hopkinsville) but it will be close.
The entire region should prepare for a dangerous severe weather
event through early this evening.
Strong south winds will continue through the afternoon and shift
to the west. Winds Saturday are currently forecast below advisory
criteria.
.LONG TERM...(Monday through Friday)
Issued at 148 PM CDT Fri Mar 31 2023
Main focus of the long term period is thunderstorm/severe potential.
12z guidance is in a little better agreement on timing and
placement. Models hint at a little bit of precip potential Monday
night in a fairly neutral upper level environment but still think
capping probably wins that battle and keeps us mostly dry. By
Tuesday afternoon strong moisture return is fed by an approaching
upper level trough over the western Plains. Our dewpoints rise into
the mid to upper 60s. GEFS shows a bit of a spread between 62-68 for
dewpoints. Aloft the subtropical and polar jets phase over TX/OK
with a broadly diffluent region moving over the area around peak
heating. GFS/ECMWF forecast soundings how fairly marginal mixed-
layer instability due to poor low-level lapse and drier air but
shear values are highly conductive as low level winds ramp up ahead
of the approaching trough.
Stronger forcing moves through by Wednesday morning. The GFS lags
the front a little slower than the ECMWF leaving the potential for a
Thursday daypart FROPA. Instability and shear look favorable for
severe. In summary will need to watch the lead wave Tuesday night
for severe potential with a better chance on Wednesday when the
front moves through.&&
.AVIATION...
Issued at 1224 PM CDT Fri Mar 31 2023
Deteriorating flight conditions are expected this afternoon as a
line of severe thunderstorms approach from the west. A decrease to
prevailing MVFR is possible with showers popping up in a few
spots. Attempted to time the most likely time for storms with
tempo groups. Winds will be strong out of the south and shift to
the west, remaining strong after a cold front arrives this
evening. Skies should remain prevailing VFR behind the front.
&&
.AVIATION...
Issued at 1224 PM CDT Fri Mar 31 2023
Deteriorating flight conditions are expected this afternoon as a
line of severe thunderstorms approach from the west. A decrease to
prevailing MVFR is possible with showers popping up in a few
spots. Attempted to time the most likely time for storms with
tempo groups. Winds will be strong out of the south and shift to
the west, remaining strong after a cold front arrives this
evening. Skies should remain prevailing VFR behind the front.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory until 1 AM CDT Saturday for ILZ075>078-080>094.
MO...Wind Advisory until 1 AM CDT Saturday for MOZ076-086-087-100-
107>112-114.
IN...Wind Advisory until 1 AM CDT /2 AM EDT/ Saturday for INZ081-082-
085>088.
KY...Wind Advisory until 1 AM CDT Saturday for KYZ001>022.
&&
$$
UPDATE...JGG
SHORT TERM...JGG
LONG TERM...JGG
AVIATION...JGG