Expected impacts:
- There is a slight chance of an
isolated shower or thunderstorm this evening or early tonight, but the
majority of the area will likely remain dry
- There is a chance of an
isolated shower or thunderstorm on Wednesday afternoon or Wednesday
evening, but the more widespread activity is likely to remain further to
the North of the local area
- Scattered showers and
thunderstorms are possible from Wednesday night into the pre-dawn hours of
Thursday morning
- Locally heavy downpours of rain
are possible at times with any thunderstorms in the affected portions of
the area
Discussion:
We know that you depend on us to provide the most accurate, dependable weather
forecasts that we possibly can, and that's indeed what we strive to do on a
daily basis. However, we are, after all, talking about predicting the future,
and sometimes that's just downright difficult to do. This certainly applies to
the next 24-36 hour period across the local area.
At this time we are unable to be as confident as we would like to be regarding
the forecast, particularly for the Wednesday afternoon and evening into Wednesday
night time period. This is because there are numerous variables in play - many
more than usual - which will determine the eventual outcome of the local
situation. We will continue to closely monitor these variables, utilizing all
of the tools, technology and experience that we have available, and issue
appropriate updates as the situation evolves. This is one of those situations
where you want to continue monitoring our updates for the latest thinking and
trends as they occur. Right now, our best efforts have produced the below, and
we submit it for your review:
...This Evening and Tonight - Confidence: Moderate to High...
There is a slight chance of an isolated shower or thunderstorm this evening
into early tonight, but the vast majority of the local area is likely to remain
dry.
...Wednesday Afternoon and Wednesday Evening - Confidence: Moderate...
There is a chance of an isolated shower or thunderstorm on Wednesday afternoon
or Wednesday evening, however at this time, the majority of the more numerous
to widespread activity is expected to remain to the North of the local area
during this time period. If a thunderstorm is able to develop during the
Wednesday afternoon or evening time period, it could produce hail and/or
strong, gusty winds in the affected parts of the area. There is still a
moderate amount of uncertainty with regard to the Wednesday afternoon and
evening time period at this time, and we'll continue to attempt to better
identify local thunderstorm potential for any necessary later updates.
...Wednesday Night/Pre-Dawn Thursday - Confidence: Low to Moderate...
Scattered showers and thunderstorms are possible from Wednesday night into the
pre-dawn hours of Thursday morning, assuming that some of the activity which
forms to the West during the afternoon and evening on Wednesday organizes and
moves East/Southeast into the local area. Please be aware that this is far from
certain, as there are numerous indicators that suggest the activity will once
again remain to the North of the local area during the Wednesday night to
pre-dawn Thursday time period. We will continue monitoring for any changes in
trends during this time period.
...Expectations with any Thunderstorms During any of the Above Time Periods -
Confidence: High...
Regardless as to the coverage of any thunderstorm activity during the above
mentioned time periods, locally heavy downpours of rain are possible at times
with any thunderstorms in the affected portions of the area. Also, as noted
above, any thunderstorm that manages to form on Wednesday afternoon or evening
could also produce hail and/or strong, gusty winds in the affected portions of
the area.
Expected impacts:
- Scattered showers and isolated
thunderstorms are possible through 2pm
- Showers and thunderstorms are
expected to become more numerous toward/after 2pm, on into the early to
mid-evening hours
- Locally heavy rainfall is
likely at times with thunderstorms especially later this afternoon into
early this evening, which could produce flooding at times in low lying and
poor drainage areas
- Storm total rainfall of 2-3
inches is expected across most of the area, with localized amounts of 3-4
inches possible in some spots
- A few strong to severe
thunderstorms could also produce strong, gusty winds and/or hail in at
least some parts of the area later this afternoon into early this evening
Discussion:
...Near Term Update and Forecast...
The shower and thunderstorm activity that moved through the area this morning
continues to shift off to the South and East of the area at this time, and has
formed into a solid line from near San Antonio to Seguin to Bastrop. This
activity has effectively cut-off the flow of moisture into the area from the
Southeast, and has, at least temporarily, resulted in a significant
stabilization of the local atmosphere (note the cool, North breeze across the
area at this time).
The above mentioned boundary now to the South of us, called an outflow
boundary, is expected to stall soon as Southerly winds increase in Deep South
Texas. One of two things will then happen this afternoon: 1). The boundary will
hold nearly stationary to the South of the area through the afternoon, thereby
keeping the highest risk of strong to severe thunderstorm activity to the South
of the local area where the air is more unstable or 2). the boundary could
start lifting back Northward and reach at least some portions of the local area
later this afternoon. If scenario 2 were to occur, it would most likely be into
southern portions of the area (i.e., Hays County), with decreasing probability as you move Northward.
If scenario 2 occurs, then there will be a risk of strong to severe
thunderstorm activity, with hail and/or strong, possibly damaging wind gusts in
the affected areas, as well as very heavy downpours of rain and of course,
lightning. This would occur mainly from toward/after 2-3pm through about 7-8pm.
If scenario 1 occurs, then we can expect scattered to numerous showers and
scattered thunderstorms, some of which could produce small hail in some parts
of the area, as well as locally heavy downpours of rain, this afternoon into
early this evening.
Regardless as to which of the above scenarios takes place, all shower and
thunderstorm activity should move East out of the area by around 8-9pm this
evening, based on present trends.
We will continue monitoring the progress and/or return of the outflow boundary
during the midday and afternoon hours and issue additional updates as trends
become identified.
...Expected Rainfall and Possible Low Land Flood Risk...
Regardless as to which of the above scenarios takes place, locally heavy
downpours of rain will be likely again at times in many parts of the area
during the afternoon (especially toward/after 2-3pm) into the early evening
hours. Heavy rain will be more widespread if scenario 2 occurs, and less
widespread (more scattered to regional in nature) if scenario 1 occurs.
Any periods of heavy rainfall this afternoon into early this evening may result
in mostly minor flooding of low lying and poor drainage areas, such as low
water crossings and similar areas. If scenario 2 above occurs, and the heavier
rain is more widespread, runoff may continue well into the late evening and
overnight hours, well after the falling rain has ended, in the affected areas.
We will continue monitoring the
situation and issue updates and/or specific alerts/warnings as conditions
warrant.
Expected impacts:
- Scattered to numerous showers
and isolated thunderstorms are likely this morning
- Showers and thunderstorms are
likely this afternoon into early-mid evening
- Locally heavy rainfall is
likely at times with thunderstorms especially this afternoon/early evening,
which could lead to flooding at times, especially in low lying and poor
drainage areas
- Present indications suggest
that rainfall is likely to average 2-3 inches across most of the area,
with localized amounts of 3-4 inches possible in some spots
- A few strong to severe
thunderstorms could produce strong, gusty winds and/or hail this
afternoon; a more organized line of strong to severe t-storms is possible
mainly from 4pm-7pm
Discussion:
...This Morning...
Scattered to numerous showers and isolated thunderstorms will continue across
the area this morning. Outside of any isolated thunderstorms, most of the rain
this morning is expected to be light to moderate in intensity for the most
part. Any isolated thunderstorms could produce locally heavy downpours of rain
in the affected portions of the area.
...This Afternoon and Evening...
Showers and thunderstorms are expected to increase in number and intensity
during the afternoon hours today and continue until about 7-8pm this evening.
Locally heavy rainfall is likely at times with some of this activity, which
could lead to flooding at times in at least some parts of the area, especially
in low lying and poor drainage areas such as low water crossings and similar
parts of the area. In addition, a few stronger thunderstorms could produce
strong, gusty winds and/or hail in some parts of the area this afternoon into
early this evening.
It is also possible that a more organized line of thunderstorm activity could
move into the area late this afternoon/early this evening, especially between
4pm and 7pm. If this occurs, an enhanced possibility of strong, possibly
damaging wind gusts could result, and isolated spin-up type tornadoes sometimes
occur with such activity as well. The reason we're saying "could move into
the area" is that there is uncertainty at this time as to whether the line
will develop to the immediate West of the local area and then move East across
the area, or whether the line will not form until the associated frontal
boundary moves to the immediate East of I-35 during the 4-7pm time period. This
aspect of the situation should become more clear around midday today or early
this afternoon, and we'll provide additional information as the situation
unfolds.
...Expected Rainfall and Possible Low Land Flood Risk...
Present indications suggest that rainfall is likely to average 2-3 inches
across most of the area, with localized amounts of 3-4 inches possible in some
spots. About 25 percent of that amount is expected to occur this morning, with
the majority of the remainder likely to occur this afternoon into early this
evening.
Present indications suggest the primary time of concern for possible low land
flooding to develop will be from around 2-3pm through about 8-9pm this
afternoon/evening. Depending upon the coverage and amount of heavy rain, a low
land (i.e., low water crossing, etc.), a flood condition could linger into the
pre-dawn hours of Thursday, well after the falling rain has ended (as runoff
from earlier rain will continue). If the heavier rain does in fact exit the
region by 7-8pm this evening as is currently expected, then any flood condition
of low water crossings, etc., should decrease during the pre-dawn hours of
Thursday, before the morning rush period begins, but again, this will depend on
the extent of the afternoon/early evening activity overall.
...Strong to Severe Thunderstorm Risk this Afternoon/Early this Evening...
A few stronger thunderstorms could produce strong, gusty winds and/or hail in
some parts of the area this afternoon into early this evening. It is also
possible that a more organized line of thunderstorm activity could move into
the area late this afternoon/early this evening, especially between 4pm and
7pm. If this occurs, an enhanced possibility of strong, possibly damaging wind
gusts could result, and isolated spin-up type tornadoes sometimes occur with
such activity as well. Details on this possibility should become more clear
during the midday/early afternoon hours as activity evolves.
Expected impacts:
- Scattered showers and
thunderstorms are expected to develop just before dawn on Wednesday, and
then increase into the daytime and evening hours on Wednesday
- Present indications suggest
that locally heavy rainfall is likely at times with this activity across
much of the local area
- Periods of heavy rainfall may
lead to flooding at times, especially in low lying and poor drainage
areas, which could extend beyond the time the rainfall ends, into early
Thursday morning
- Present indications suggest
that rainfall is likely to average 2-4 inches across most of the area,
with localized amounts of 4-6 inches possible in some spots on Wednesday
- In addition to the threat of
locally heavy rainfall, a few of the thunderstorms could also produce
strong, gusty winds and/or hail in some parts of the area during the day
on Wednesday
Discussion:
Scattered showers and thunderstorms are expected to develop just before dawn on
Wednesday, and then increase in number and intensity into the daytime and
evening hours on Wednesday. Present indications suggest that locally heavy
rainfall is likely at times with some of this activity, potentially across
large portions of the area.
Present indications suggest that rainfall is likely to average 2-4 inches
across most of the area, with localized amounts of 4-6 inches possible in some
spots. The majority of the rainfall is expected to occur during the period 6am
on Wednesday morning to 12 Midnight on Wednesday night.
Periods of locally heavy rainfall may lead to flooding at times, especially in
low lying and poor drainage areas, which could extend beyond the time the
rainfall ends, into early Thursday morning. While present indications
suggest that the rain itself will end around Midnight on Wednesday night,
runoff will likely continue into the pre-dawn and early morning hours of
Thursday, which could cause a low land flood risk to extend into the Thursday
morning rush period. The extent to which this occurs will obviously be highly
dependent upon the exact amount and coverage of rainfall on Wednesday/Wednesday
evening.
Impacts from low land flooding are possible both for the afternoon/evening rush
period on Wednesday, as well as the morning rush period on Thursday. As the
precipitation is currently expected to be more in the developmental stages
early on Wednesday morning, significant impacts appear unlikely for the
Wednesday morning rush time period, but that could change in future updates if
significant shifts in timing occur.
In addition to the threat of locally heavy rainfall, a few of the thunderstorms
could also produce strong, gusty winds and/or spotty hail in some parts of the
area during the day on Wednesday, especially during the afternoon and early evening
hours.
We will continue monitoring the situation and issue updates as conditions
warrant.
Forecaster Confidence (Low/Moderate/High):
Moderate to High
