Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/28/24
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
526 PM CST Tue Feb 27 2024
...New AVIATION...
.SHORT TERM...
(Tonight through Wednesday night)
Issued at 200 PM CST Tue Feb 27 2024
Our region remains situated underneath the southern extent of an
amplified jetstreak as a mid-level trough continues to advect
eastward across the northern plains today. Mesoanalysis indicates
light southerly winds at the surface across the region this
afternoon as the pre-existing stratus continues to wane in areal
coverage. Moisture remains confined to the lower levels of the
boundary layer as a dry airmass remains firmly in place in the mid
levels of the vertical column. 18z ACARS data from KSAT indicates the
continued presence of an stout inversion just above the surface at
this hour. With mixing heights increasing, vertical mixing could
allow for some drier mid-level air to mix down to the surface
resulting in lower relative humidities across the region through the
mid afternoon hours. With the erosion of the low level cloud deck,
insolation will allow for temperatures to climb through the afternoon
hours reaching forecast high temperatures in the upper 80s to low
90s across the I-35 corridor this afternoon. Locations across the
western half of our area will once again reach the middle to upper
90s as a surface dry line propagates eastward across the region. With
winds behind this boundary out of a southwesterly direction,
temperatures will trend higher than points further eastward.
After sunset tonight, winds will decouple across the area
with surface winds veering to a southeasterly direction. This will
allow for moisture return to advect into the eastern half of the
region across the low-level boundary layer. With light winds across
the area and ample low level moisture, patchy dense fog may once
again be observed across areas along and east of the I-35 corridor
on Wednesday morning. Forecasted low temperatures will range from
the low to mid 50s across the northern half of our area to
temperatures in the low to mid 60s across our southern extent.
With the advection of the mid-level trough further east across the
country, an associated surface low and cold front will propagate
southward across the plains. By Wednesday, this moderate to strong
cold front will sweep into the region packing some gusty winds and
fire weather impacts, but will bring little cold air advection into
the region. A big part of the cool-down will be due to the increase
low level cloud-cover on Wednesday. Some elevated showers could
drift across the region, but there haven`t been any signals for
anything other than mid-level showers that could fall mostly as
virga. High temperatures on Wednesday are forecast to range from the
low 60s across the northern half of the CWA, upper 60s to low 70s
along the I-35 corridor and middle to upper 70s across the majority
of the southern areas of the CWA.
&&
.LONG TERM...
(Thursday through Tuesday)
Issued at 200 PM CST Tue Feb 27 2024
With the mid-level trough advecting eastward into the Great Lakes
region, a mid-level ridge will build in across the region aloft.
Northerly winds will be on the decrease Wednesday night as surface
high pressure continues to build in from the north. The models have
trended upward with overnight low temperatures Wednesday night/
Thursday morning, resulting in expected readings mainly in the 40s to
near 50 degrees. Surface high pressure and plenty of cloud cover
will keep highs on Thursday down in the mid 50s to low 60s.
Precipitation chances for both Wednesday night and Thursday are not
favorable and we will keep chances in the 20-30% range for the
southern Edwards Plateau, Hill Country and portions of the I-35
corridor from San Marcos northward.
For Friday through the upcoming weekend, the forecast will trend back
to warm and dry. Highs on Friday will quickly rebound back into the
mid 70s to lower 80s, then rise into the upper 70s to mid 80s
through the weekend. Lows will mostly remain in the mid 50s to lower
60s.
The medium range models keep southwesterly flow aloft over our region
on Monday, but differ with regards to the strength of an upper trough
axis moving across the central and high plains states. The GFS and
Canadian are stronger and deeper with the trough axis and manage to
bring the next cold front into the region Monday, while the ECMWF
shows the front moving in just beyond the current forecast period.
Any temperature changes behind this front look to remain fairly
minimal at this time.
&&
.AVIATION...
(00Z TAFS)
Issued at 525 PM CST Tue Feb 27 2024
Southerly flow continues this evening with high clouds overhead.
Some low clouds may make it into the Coastal Plains tonight along
with areas of fog, but recent trends keep any dense fog out of the I-
35 corridor. A cold front moves into South Central Texas from the
north after 06Z which will shift winds from the north at TAF sites
with its passage. Expect gusty wind to quickly move in behind this
feature with gusts up to 30 knots likely at I-35 sites and up to 25
knots at DRT through the afternoon.
&&
.FIRE WEATHER...
Issued at 200 PM CST Tue Feb 27 2024
Localized elevated fire weather conditions remain possible this
afternoon for locations in the Hill Country, Southern Edwards
Plateau and along the Rio Grande that align west and north of the
wavering dryline in the afternoon. Minimum relative humidity lower
into the 10 to 25 percent range while winds may become as high as 10
to 15 knots from out of the south- southwest to west-southwest.
The front for Wednesday will bring near critical to critical fire
weather conditions to parts of the Edwards Plateau, Hill Country and
Rio Grande Plains, but there is some concern about a short time
window and the amount of cooling and cloud cover that would push RH
values in the teens. We could be facing a need for an RFW, but with
the values just barely inside the favorable criteria, this may be
addressed in a later forecast package.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 55 66 47 56 / 0 0 0 20
Austin Bergstrom Intl Airport 55 67 47 58 / 0 0 0 20
New Braunfels Muni Airport 56 70 47 58 / 0 0 0 20
Burnet Muni Airport 50 63 44 56 / 0 0 10 30
Del Rio Intl Airport 65 76 51 68 / 0 10 10 20
Georgetown Muni Airport 53 64 47 58 / 0 0 10 30
Hondo Muni Airport 59 72 47 59 / 10 10 0 10
San Marcos Muni Airport 56 69 47 58 / 0 0 0 20
La Grange - Fayette Regional 57 66 49 56 / 0 0 0 10
San Antonio Intl Airport 58 71 48 58 / 0 0 0 10
Stinson Muni Airport 60 73 50 59 / 0 0 0 10
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term...27
Long-Term...05
Aviation...27
Area Forecast Discussion
National Weather Service Indianapolis IN
908 PM EST Tue Feb 27 2024
.Key Messages...
- Strong to possibly severe weather this evening and overnight
- Windy conditions develop tonight and persist into Wednesday
- Much colder for Wednesday with wind chills in the teens and 20s
- Few rain/snow showers Friday...otherwise a seasonable/mainly dry
end to the workweek
- Moderation this weekend...very mild, rain chances early next week
&&
.Mesoscale Update...
Issued at 908 PM EST Tue Feb 27 2024
A moisture tongue has extended our in front of a dry line over
eastern IL. Within this region dew points are near to just above
60F. The moisture advection is likely the cause of isolated attempts
at convective initiation, but the storms have yet to be able to
break the LFC and sustain themselves. This moisture tongue has also
cause the dry-line to start receding slightly, ending the threat of
dry-line created vertical lift. Initiation over the next few hours
therefor looks unlikely, unless the isentropic lift becomes robust
enough to break a shallow remnant layer of CIN.
The second threat associated with an advancing cold front is still
in play for the overnight period. Surface analysis depicts a strong
and quickly advancing cold front over western IL, currently progged
to reach western portions of Indiana between 10 and 11EST. Initial
convection still looks to have a more discrete mode with shear
vectors orthogonal to the front. Also of note is the projected rapid
nocturnal strengthening of the LLJ, leading to very high near
surface SRH along with sustainable 0-3km buoyancy. This creates the
potential for supercells to develop along the front, with all modes
of severe hazards possible. Timing of supercell potential is highest
between 11PM and 2AM, with this threat contained to south of the I-
70 corridor. As the storms grow upscale, a destructive wind threat
becomes the primary concern. Peak linear wind threat for south
central Indiana will be between 1AM and 4AM.
&&
.Forecast Update...
Issued at 908 PM EST Tue Feb 27 2024
Details about the severe threat are in the Mesoscale discussion.
Convection across southern Illinois has struggled to maintain itself
without any significant forcing. Additional isolated light returns
have been noted on radar in southern portions of central Indiana,
but these haven`t done much either. Will continue to keep a close
eye on development, but for now will lower PoPs in the very short
term.
Hi-res models, including the Warn-on-Forecast System, continue to
develop scattered convection across southern portions of the area
before midnight. Afterward, more widespread shower and thunderstorms
will develop and move into the area as the cold front approaches
from the west. Focus looks to be on the far southern portions of the
area.
Given the above, will keep high PoPs going in the south third or so
of the area, but will lower PoPs north and tighten the gradient
between chance and higher category PoPs.
The temperature gradient behind the front is impressive and the
difference in airmasses can be seen on infrared satellite.
Temperatures will still continue to fall quickly toward morning, and
no significant changes will be made to temperatures.
Winds are gusting to over 30kt already in the west, and these will
spread east during the night.
&&
.Short Term...(This evening through Wednesday)
Issued at 300 PM EST Tue Feb 27 2024
Severe Threat...
Overview:
A short wave attached to a robust subtropical jet will move
through the Great Lakes and Ohio Valley region today through
tonight. Within this short wave a quickly deepening low pressure
system, of which is currently over the Quad Cities region,
progressing northeastward. Attached to the low, there is a dry line
(currently over central Illinois), and a lagging cold front over
Iowa/Missouri.
Soundings show plenty of deep shear including modest 10-15mph
southerly surface winds, veering to 30-40kt SSW low levels and 100+
kt westerly jet above 300mb. It total, sfc-6km bulk shear values are
between 70-80kts, plenty to sustain organized convection. Mid-level
lapse rates also support strong updrafts, ranging from 8.5-7.5 C/km
in the 850-500mb layer.
The limiting factors for the severe threat are the presence of a
strong EML and associated cap this afternoon, as well as the lack of
surface based lift along the dry-line.
Current ACARs soundings and a sounding taken at Valparaiso
University showcase this cap well with a decrease in dew points
above 900mb, with a simultaneously sharp increase in temperatures with
height. A stagnant cloud deck around 2500ft is further reinforcing
the cap. A secondary warm front is slowly progressing northward,
helping erode some of this cloud layer as seen on day-cloud
satellite imagery, and should help break the cap by this evening,
but for now, this will remove the chances for thunderstorm
initiation over the next 2-4 hours.
As mentioned, the second limiting factor is the amount of surface
based forcing along the dry-line. Further north, orthogonal surface
flow across the dry-line should lead to better initiation this
evening, but over central Indiana, the lack of confluence along the
dry-line is concerning for initiation potential. Still, latest
guidance is showcasing a bit more progression of the dry-line, of
which could lead to isolated thunderstorm initiation. The better
threat for initiation will be along the cold front tonight, primarily
over southern Indiana where the front is situated W/E along the
nocturnal LLJ.
Location and Timing:
The initial severe threat will be associated with the dry-line
advancement, in combination with the cap erosion between 7PM and
10PM EST. As discussed in the previous segment, confidence is low
that initiation will occur, but parameter spacing is supportive of
severe, rotating convection if any does initiate. This threat is
for all of central Indiana, but most likely occurrence is along
and north of the I-70 corridor.
The second severe threat will be associated with the cold front
passage between 10PM and 4AM tonight. As the cold front passes
through, any remaining CIN from the cap should be minimal, and
initiation should occur. This especially trough where the cold front
begins to stall and is oriented more W/E along a strengthening 50-
60kt LLJ. The best chance for the W/E oriented front will be over
southern Indiana as highlighted by an Enhanced Risk by SPC.
Rest of This Afternoon (before 00Z)...
Generally quiet weather is expected across much of central Indiana
this afternoon. Lower clouds have kept temperatures in check (but
still unseasonably warm for late February). Some thinning of the
clouds is possible so temperatures may still jump into the lower
70s.
Lack of forcing and some capping will likely keep most of the area
dry through this period. Isolated convection (potentially severe)
may develop closer to 00Z, so will have some low PoPs.
Tonight...
Forcing will increase as an upper trough gets closer and a cold
front approaches this evening. Scattered convection will develop
with instability present. Will have some chance PoPs for much of the
evening.
Late evening into the overnight, convection will increase in
coverage as forcing increases with the approaching upper trough and
with the cold front. A strong upper jet and a continuing low level
jet will also be around.
Convection that fired earlier in the evening across Missouri and
southern Illinois will move into the southern forecast area as well
late evening into the overnight. Will go high PoPs across the south
during this time frame.
Questions remain though about coverage across the north. The surface
low and warm front will be well north of the area early overnight.
Although the strong cold front will provide good forcing, the
convection to the south may rob some of the deeper moisture for the
northern forecast area. Will go no higher than likely PoPs north and
perhaps even only chance for some areas.
Gradient winds will become a concern tonight. Mixing will occur
ahead of the cold front, which will bring down some of the stronger
winds aloft. As the cold front passes, strong cold advection will
bring down winds as well.
Ensembles indicate the threat for some 40 mph wind gusts but are
less bullish with 45 mph winds (or sustained winds of 30 mph). Thus,
do not plan on a Wind Advisory at this time, but will continue to
monitor in case winds overperform.
Temperatures will remain quite warm until the cold front passes late
tonight, then readings will fall rapidly into the 30s and 40s by 12Z.
Wednesday...
The cold front will be through much of the area by 12Z and thus most
of the forcing. Some forcing will linger with the upper trough
itself though, so will keep some low PoPs most areas by the start of
the Wednesday period. Drier air will then quickly move in and end
any precipitation.
As cold air rushes in, any linger precipitation will change to snow.
Little or no accumulation is expected with very light QPF amounts
and a warm ground.
Windy conditions will persist with the strong cold advection. Gusts
up to around 40 mph will persist into the day.
The cold advection will keep temperatures in the 30s. Thanks to the
wind, wind chills will be in the teens and 20s. After air
temperatures in the 60s and 70s the days prior, this will feel even
worse.
&&
.Long Term...(Wednesday night through Tuesday)
Issued at 300 PM EST Tue Feb 27 2024
Wednesday Night through Friday...
The continual roller-coaster pattern over the Midwest, as we
transition from winter to spring, should inclue one almost-blustery
period Wednesday night as the column`s thermal minimum under the
passing trough advances quickly from central Indiana`s eastern
counties to the Appalachians. WNW surface winds, still gusting to 25
mph early in the evening will subside as the corresponding surface
high pressure center slides east across Kentucky, pushing the
tighter gradient ahead of it. Readings should have no problem
falling into the low 20s under mostly clear skies...which would be
35 degrees below Tuesday`s minimums...and set-up Thursday to be only
the fourth sub-normal day of February 2024.
The late work-week will then feature a broad and pronounced split
flow progressing across the western/central CONUS. Potential
moderation will be delayed by a short wave lifting from the southern
Plains to the eastern Great Lakes...which will provide clouds and at
least isolated light rain and/or snow showers across the southern
Midwest Friday. Little or no impacts expected from any flurries/
snow showers. Temperatures Thu-Fri are expecetd to show slow
moderation through near to slightly above normal levels.
Saturday through Tuesday...
A more pronounced moderation will then be the rule as a progression
similar to that of early this week takes place. The pattern will
transition from a subtle upper zonal ridge into increasing southerly
flow ahead of a deep, broad upper trough that will steadily progress
across the western CONUS through the weekend. Ensembles then
indicate very amplified surface low pressure, along the trough`s
front end, from Canada down the Mississippi Valley...should
faciliate another slower frontal passage within the early workweek.
Cold late winter high pressure under the trough`s core should slide
along the Canadian border, with a more moderated cool down expected
as far south as our CWA into the mid-week.
Probably at least a 12-24 hour period of organized rain showers
would be expected, with at least embedded general thunder. The
convective opportunity here appears modest so far with what should
be minimal shear, lower instability, and perhaps storms well to our
south zapping much of the local region`s potential. THe bigger
story should be at times robust southerly breezes through the early
week promoting unseasonably high temperatures closer to records than
normals...with a "weaker" record high minimum on Monday (55F)
perhaps obtainable. The normal max/min at Indianapolis throughout
the long term is 46/29.
&&
.Aviation...(00Z TAF Issuance)
Issued at 621 PM EST Tue Feb 27 2024
Impacts:
- Non-convective low level wind shear through about 07Z
- Wind gusts 25 knots or more through much of the period
- Wind shift to the northwest roughly 06-10Z time frame
- Scattered to numerous convection into the early overnight
Discussion:
Low confidence in convective coverage with this issuance, with
perhaps convection remaining north and south of the sites. Most
likely site to see convection looks to be KBMG.
Low level jet will bring non-convective low level wind shear through
about 07Z. Some of these winds will mix down creating gusts at the
surface.
Strong cold front will move through overnight shifting winds and
increasing gusts. MVFR ceilings will occur behind the front then
skies will scatter out by Wednesday afternoon most sites.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale...Updike
Update...50
Short Term...50/Updike
Long Term...AGM
Aviation...50