Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/01/17
Please see the 00Z aviation forecast discussion below.
VFR conditions will continue through this evening at area TAF sites.
We do expect low clouds to redevelop after midnight and will continue
to mention MVFR cigs along I-35 beginning 08-09Z. We will see a
steady stream of mid and high level moisture overnight and this may
disrupt the onset of low clouds. For now, we will stick with the
above timing and continue to monitor. Attention will then turn to a
cold front set to move through early tomorrow morning. First, a
dryline/weak Pacific front will shift winds to a more northwesterly
direction at DRT around 06Z, with the I-35 sites becoming
west/northwest around 09-10Z. Winds will then increase around 15-16Z
at all TAF sites as a surge of high pressure moves into the region.
Winds will likely remain gusty through tomorrow afternoon, then begin
to diminish around 02/00Z.
PREV DISCUSSION... /ISSUED 301 PM CST Tue Feb 28 2017/
SHORT TERM (Tonight through Wednesday)...
A mostly dry cold front will shift through the area overnight and
early Wednesday morning with only light showers at best along it.
Northwest winds and drier air will filter into the region through the
afternoon with only high passing clouds remaining.
RAP analysis coupled with water vapor imagery channels clearly
depicts a longwave trough axis over the Rockies and into the desert
southwest. A sharp moisture gradient exists between San Antonio
northwestward to San Angelo where dewpoints are in the upper 60s to
lower 40s, respectively. As the passage of the trough axis occurs
over the next 18 hours, stronger northward momentum will bring the
drier and slightly cooler airmass into South-Central Texas. With the
strongest forcing well north and nearly parallel mid-level flow,
dynamic support will be lacking with the frontal passage early
Wednesday morning. Light showers to sprinkles may be all that is
mustered (if even that much) along the front as it passes through.
Patchy areas of fog could be possible ahead of the front from 4am-9am
before it moves through. Low clouds will clear through the late
morning with only high passing cirrus remaining intact through the
overnight and Thursday morning with continued brisk zonal to weakly
SW flow in the mid-levels.
LONG TERM (Thursday through Tuesday)...
Coldest mornings in a while will occur Thursday and Friday with a
few mid and upper 30s in the Hill Country. Rain chances increase
going into the weekend as a slow moving and weakening mid- and
upper-level system shift over the region.
Much drier air will shift into the region by late Wednesday and
Thursday morning as dewpoints drop into the upper teens and low 20s.
Thankfully, the continued brisk H5-H3 flow over the region will allow
for cirrus cloud generation that should help blanket the region and
keep low temperatures from fully bottoming out. A few pockets in the
Hill Country could still reach down into the mid and upper 30s but no
freezing temperatures are currently expected at this time. Thursday
highs will be 10 degrees cooler than today. This will bring us to
below normal lows but near average highs.
By late week, a cut-off mid and upper-level low is expected to shift
across west Mexico and slowly move towards central and south Texas
over the weekend. Moisture return will start Friday as mid- and
upper-level lifting support remains farther west. Best rain and
isolated thunderstorm chances remain on Saturday and Sunday as either
an ejecting shortwave of energy or the weakening parent low shift
over the region. The best moisture availability vs. the strongest
forcing does not appear to line up well. Strongest lift looks to
occur Saturday but the best moisture return wont occur all the way
till Sunday when the forcing is weaker. All told, have a persistent
30-50% rain and thunderstorm chance Saturday through Sunday for
central and eastern locations. While isolated pockets of heavy rain
may occur on Sunday towards the coastal plains with the deeper
moisture, hazardous conditions do not look likely at this time.
Models continue to be in poor agreement beyond the weekend and a
blend with higher GFS weighting was used for days 6 and 7 forecast.
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 62 73 45 67 44 / 10 10 0 0 0
Austin Bergstrom Intl Airport 61 73 43 67 42 / 10 10 0 0 0
New Braunfels Muni Airport 62 75 44 67 44 / 10 10 0 0 -
Burnet Muni Airport 55 68 39 63 39 / 10 10 0 0 0
Del Rio Intl Airport 56 78 45 69 45 / - - 0 0 0
Georgetown Muni Airport 58 69 41 65 41 / 10 10 0 0 0
Hondo Muni Airport 59 79 42 69 44 / 10 10 0 0 0
San Marcos Muni Airport 61 74 43 67 43 / 10 10 0 0 -
La Grange - Fayette Regional 66 75 43 67 44 / 10 10 0 0 -
San Antonio Intl Airport 62 77 45 68 46 / 10 10 0 0 -
Stinson Muni Airport 63 78 46 68 47 / 10 10 0 0 -
Public Service/Data Collection...Treadway
Area Forecast Discussion
National Weather Service Houston/Galveston TX
912 PM CST Tue Feb 28 2017
Strong WAA continues and seeing a lowering of CIGS across the
southern CWA. Made some adjustments to the current forecast based
on 18z guidance and latest obs. Expect mostly cloudy to cloudy
conditions overnight with well above normal temperatures. Light
fog across the south will likely thicken overnight and patchy
dense fog will probably develop in the nearshore waters/bays and
coastal areas. Will probably issue a Marine Dense Fog Advisory
for Galveston Bay/Eastern Nearshore waters. Cold front moving
into the Panhandle and is forecast to move through SETX Wednesday
morning and into the coastal areas in the early afternoon with a
prefrontal trough a few hours earlier turning the winds to the
sw/w. Deep dry air sweeps across in the wake of the front with
heating in the afternoon bringing a respite from the high humidity
of the last few days. Rain chances are low this evening with a
strong cap in place and forecast to strengthen over most of the
CWA through 09z. Eastern areas could mix out the cap enough to see
scattered showers/isolated thunderstorms toward morning-mid
morning. By afternoon expect rain chances to be almost entirely
out over the Gulf waters.
.PREV DISCUSSION... /ISSUED 604 PM CST Tue Feb 28 2017/
A mix of IFR to VFR ceilings across the terminals late this
afternoon will deteriorate into the IFR to MVFR range this evening
as cooling results in additional saturation beneath an inversion
located around 900 MB on aircraft soundings out of Houston. LIFR
ceilings and visibilities are possible at Galveston by 06Z as sea
fog along the coast advects inland. Surface analysis as of 23Z
shows an approaching cold front pushing into Oklahoma from Kansas,
with this boundary crossing the terminals 12-18Z Wednesday. An
elevated surface pressure gradient ahead of the front will keep
southerly winds around 10 knots through the evening but a
prefrontal trough will result in a west/southwest wind shift ahead
of the front early Wednesday morning. A few isolated SHRA
possible along the prefrontal trough as it moves south ahead of
the front at Conroe and terminals south with a brief period for
patchy fog also possible for inland terminals as winds decrease
below 10 knots with the prefrontal trough`s approach.
Ceilings and visibilities are expected to rapidly improve behind
the front as drier air moves into the region, with VFR conditions
becoming established by 12-15Z Wednesday. Elevated northerly winds
10-15 knots with stronger gusts 20-25 knots are expected behind
the front by Wednesday afternoon.
PREV DISCUSSION... /ISSUED 403 PM CST Tue Feb 28 2017/
A partly to mostly cloudy Tuesday with interior surface temperatures
pushing into the lower 80s...drier air mixing down providing
cloud breaks that may allow a few sites to briefly achieve the
middle 80s as we close out this warmest February on record. Sea
fog hanging just off the coast will likely advect inland shortly
after sunset...expecting another hazy evening and early Tuesday
especially over the (near) coastal counties. As there has been
virtually no change to this resident air mass...forecasting the
return of patchy maritime fog (locally dense pockets) similar to
this morning`s conditions. Murky...low overcast and hazy conditions
will persist over the second half of the forecast area tomorrow
morning just downstream of an approaching central Texas cold
front. This front is forecast to come through from the late
morning (north/central CWA) hours and reach the coast during the
mid-afternoon hours followed by moderate offshore inland winds...
strong over the waters...in its wake late tomorrow afternoon and
evening. There is not much column moisture to work with so expecting
tomorrow`s frontal passage to be a fairly dry one. Higher moderate
POPS reside closer to the coast with very low QPF scattered showers.
Cannot rule out an isolated (possibly elevated) storm if the
progged skinny CAPE is briefly realized but..other than that...
little fanfare to begin the month of March.
Cooler post-frontal conditions will set in later in the week that
will make Thursday and the better part of Friday pristine weather
days if a fan of mainly clear skies and more seasonable T
readings in the mid to upper 60s during day/chilly mid to upper 40
sunrise readings. Easterly winds veer around to onshore Friday
and the moisture prime will begin...near or above 99 percentile
std dev pwat air over us through the weekend. An unsettled weekend
weather pattern is still being advertised by the suite as the
ensemble members still trend towards hanging back an upper level
trough over Baja. Shortwave disturbances emanating from central
Mexico and moving up within the southwesterly steering flow will
increase mesoscale POPs that will be fine tuned from Saturday
onward. High moisture...lift from these shortwaves...possible LLJ
with enhanced upper divergence just downstream of the eastern
advancing mid-upper trough all suggest likely weekend into early
next week rain chances. A surface boundary that slowly moves into
the area and stalls either Monday or Tuesday would provide
additional low level focus that hints to an early week high
rainfall/flooding scenario. Although muddled...a consistent signal
that will likely cause a more wet than dry pattern shift from as
early as Saturday and...depending on the eastward advancement of
the trough and precedent mesoscale behavior...could persist well
into next Tuesday. 31
Moderate to occasionally strong onshore winds will prevail tonight
in response to low pressure moving toward the western Great Lakes.
Winds will veer to the southwest early Wednesday as a pre-frontal
trough crosses the coast. Warm moist air over riding cooler shelf
waters will again produce favorable conditions for sea fog tonight.
SREF and LAV guidance continue to suggest vsby falling to below a
mile at KGLS and a Marine Dense Fog Advisory may be required later
this evening. The threat for sea fog should end once winds become SW-
W and slightly drier air begins to filter into the region. A cold
front will cross the marine areas Wednesday afternoon and winds will
shift to the northwest. North winds will quickly increase Wed Night
and sustained winds between 20 and 25 knots will foster a Small
Craft Advisory for the Gulf waters through Thursday morning.
Winds will become northeast as surface high pressure settles over
North Texas. The high will shift east by Friday and sfc winds will
be come east. The persistent east wind will bring elevated seas and
tide levels to the upper Texas coast. Another SCA may be required
for the offshore waters on Friday. Tide levels are expected to
increase 1.0 to 2.0 above MLLW by Saturday morning and some minor
coastal flooding might be possible late Fri night/Sat morning. Winds
will continue to veer to the SE on Saturday as the surface high
drifts to the eastern U.S. and pressures begin to fall over the high
plains. An upper level disturbance will bring a period of unsettled
weather to the coastal waters Sat-Mon. 43
A cold front will cross SE TX on Wednesday. Considerably cooler and
drier weather will enter SE TX and RH values by afternoon will
approach 30 percent northwest of a Columbus to Huntsville to
Madisonville line. Northwest winds will also increase to 15 to 20
mph and the combination of dry grasses, moderate winds and low RH
will set the stage for potentially elevated fire weather concerns.
RH values will fall below 30 percent on Thursday but lighter winds
will preclude a threat for elevated fire weather conditions. 43
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 67 71 44 68 43 / 20 10 0 0 10
Houston (IAH) 73 79 48 69 45 / 20 30 0 0 10
Galveston (GLS) 71 75 55 66 54 / 10 40 10 0 10
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until midnight CST tonight
for the following zones: Coastal waters from Freeport to
the Matagorda Ship Channel out 20 NM...Coastal waters from
High Island to Freeport out 20 NM.
SMALL CRAFT SHOULD EXERCISE CAUTION until 4 AM CST Wednesday for
the following zones: Waters from Freeport to the Matagorda
Ship Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.
Area Forecast Discussion
National Weather Service Louisville KY
956 PM EST Tue Feb 28 2017
Issued at 955 PM EST Tuesday Feb 28 2017
Forecast has been updated to include Tornado WATCH 46 which is valid
until 500 AM EST. The tornado watch is along and NW of a line from
Simpson County to Franklin County Kentucky.
Current thinking has not really changed substantially this evening
with regards to the overnight convective evolution. The convective
allowing models have continue to suggest that convection will
continue to develop across SE MO/Far W KY and southern IL this
evening. Indeed, convective activity has increased in coverage in
this area over the last hour or so.
The only questionable convective issue is the ongoing convection
across far NE AR. This activity is moving northeast and will move
into NW TN and far W KY later tonight. There is the potential that
this activity could have an effect on the ongoing convection over SE
MO and southern IL. Nonetheless, the majority of the model guidance
suggests a cluster of convection, likely severe, will move
northeastward across southern IN and far northern KY. Recent ACARS
soundings out of SDF show the cap eroding slightly over the last
hour. There is a very pronounced elevated mixed layer with very
steep lapse rates aloft. Once this cap erodes from west to east,
the atmosphere will remain very favorable for severe weather
overnight with large hail, damaging winds, and tornadoes being
possible. This activity does look to race northeastward and may
exit our area around 500 AM EST. However, a secondary convective
line along the actual front will be sweeping in from the NW around
sunrise which will likely be a damaging wind producer. It is not
entirely clear yet if the expected overnight convection will
sufficiently overturn the atmosphere as it moves through. There are
some hints that it will in some of the latest HRRR runs. So we`ll
have to keep an eye on this overnight.
In the meantime, it is important for local residents to remain
weather aware overnight. It is important to have your severe
weather plan in place and have an efficient and reliable way to
receive weather warnings overnight.
.Short Term (Now through Wednesday Night)...
Issued at 309 PM EST Tue Feb 28 2017
...ROUNDS OF SEVERE STORMS EXPECTED THROUGH WEDNESDAY...
...NIGHT TIME TORNADOES POSSIBLE...
Several rounds of severe storms are expected to impact the region
over the next 24 hours. These could be potentially contain
significant night time tornadoes along with very large hail and
damaging winds. Be sure to have a way to get warnings tonight and
have a plan should a tornado warning be issued for your area.
Round 1 This Afternoon...
Scattered showers and storms continue this afternoon. This looks to
be the least significant potential round of storms. The convection
from this morning and cloud cover have limited the heating across
the region quite a bit. Still some storms have started to strengthen
and expect we could see a few more follow suit. With DCAPE values up
to 900 J/kg a few damaging wind gusts and marginally severe hail are
not out of the question, but most storms are expected to stay below
this threshold. These storms are expected to decrease in coverage by
00-01Z with just a few cells thereafter until the next round moves
Round 2 Late This Evening and Overnight...
This is potentially the most significant of the waves of storms. As
we go into the early evening hours, soundings show a fairly stout
cap developing. However, it looks to erode quickly during the 03-06Z
time frame. This is when the low level jet strengthens as well.
Effective shear increases to around 60 knots and storm relative
helicity values increase to 400+ m2/s2 with plenty of instability.
The next round of storms looks to move in between 03-06Z across
mainly southern IN and north and west central KY. Large hail,
tornadoes, and damaging wind will all be a possibility with these
storms. The highest chance for tornadoes will be along and northwest
of a line from Ohio county to Henry county in central KY and in
southern IN. This is where the highest chance for large hail with
supercells is as well. To the south of this line severe weather is
possible overnight, though the potential decreases the farther to
the south and east you go in central KY. It should be noted that the
exact placement of the storms tonight has been waffling a bit in the
mesoscale models this afternoon, but with the complex setup this is
expected. Anyone in the enhanced to moderate risk in particular
should take steps to stay weather aware tonight. These overnight
storms do look like they could weaken by the 09-12Z time frame with
Round 3 Wednesday...
The actual cold front will move through on Wednesday. This looks to
bring another round of severe weather. These storms look to be more
in the form of a broken squall line along and just ahead of the
front. Any capping that redevelops after the overnight storms once
again is depicted as decreasing as the front approaches. The main
concern with the storms along the front will be damaging winds,
though some hail and brief tornado spin ups are not out of the
question. A bit more questionable is out in front of the line across
south central KY where some discrete cells may develop. Should this
occur, the tornado and hail potential would be a bit higher, though
not as high as expected overnight. This line of storms along the
front should move out by mid afternoon with drying weather and
colder temps expected in its wake through the overnight hours.
Winds do look to be quite gusty out of the northwest behind the
front. Sustained winds in the 20-25 mph range are expected with
gusts of 30-35 mph. A few gusts up to 40 don`t look completely out
of the question.
.Long Term (Thursday through Tuesday)...
Issued at 222 PM EST Tue Feb 28 2017
The long term looks to be much quieter than the short term period,
at least through the weekend. Thursday should be dry and cooler with
highs in the upper 40s to lower 50s. A clipper system will drop
southeast into the Ohio Valley on Thursday night. This could bring
some light precipitation to portions of southern IN and north
central KY, mainly north of I-64. A few snowflakes could mix in with
this system, but no significant impacts are expected. Behind this
system, we will get another push of cooler air with highs topping
out in the lower to mid 40s on Friday. The cooler temperatures will
be short lived, however, as high pressure builds in and shifts
across the region through the weekend.
For the beginning of next week, another low pressure system tracking
across the upper Midwest will bring a chance for rain as a cold
front moves through. There are still significant model differences
in timing with this system, so will just go with a blend of pops for
now. Have also added in a slight chance for thunderstorms as models
do depict at least a bit of instability.
.Aviation (00Z TAF Update)...
Issued at 634 PM EST Tue Feb 28 2017
The TAF sites are in a relative lull at this hour as mid level
capping holds through the evening hours. MVFR ceilings are noted,
and are expected to persist most of the time, until cold frontal
passage tomorrow. The mid level inversion should erode after 10 PM
EST, where isolated strong and severe storms (some supercells
possible/all severe modes) are expected for round 1 of storms. Best
window will generally be in the 1 AM EST to 5 AM EST time frame at
SDF, Midnight to 4 AM EST time frame at BWG, and 2 AM to 6 AM EST
time frame at LEX. At this point, it appears most early activity
will be north of the Ohio River, but SDF will have the best shot of
the 3 TAF sites to experience a severe storms with the early round.
After a brief lull in the pre-dawn hours, a second round of storms
is expected shortly after sunrise through early afternoon along and
just ahead of a cold front. These storms are expected to be more
linear in nature and should pose a significant wind threat, to go
along with heavy rain and lightning. In addition, very gusty W or NW
winds will follow through a good chunk of Wednesday behind the cold
Left the discrete cell passage in a TEMPO overnight, and decided to
go prevailing for the second round linear storms since convection
will be more widespread. Tried to nail down the best timing for both
occurrences, and will amend as necessary. Overall, a dangerous night
is expected into Wednesday morning for aviation purposes.
IN...Flash Flood Watch through Wednesday afternoon for INZ076>079-083-
KY...Flash Flood Watch through Wednesday afternoon for KYZ023>043-