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March 20, 2015

… Flash Flood Watch in Effect Until 7pm Saturday … (Update #3)

by troyk | on Mar 20, 2015 | Comments Off

Austin / Travis County and South Central Texas Weather Update #3
Prepared by UT University/Incident Meteorologist Troy Kimmel
125pm CT – Friday / 20 March 2015


. NWS/Flash Flood Watch Effective For All of our Area at 1pm ….

. Latest NWS/West Gulf River Forecast Center Quantitative Precipitation
Forecast (QPF) Rainfall Amounts between now and 7am Sunday still suggests 3 to 4 inches locally…


NWS WATCHES / ADVISORIES / WARNINGS:
NWS /  Flash Flood Watch (Valid from 100pm Fri/20Mar2015 until 700pm Sat/21Mar2015)
Counties Included.. Williamson.. Hays and Travis (Including Austin Metro Area and IH 35
Corridor) as well as all adjacent counties
Rainfall to 3 to 4 inches or more… NWS/Austin-San Antonio forecasting isolated totals to 6 to 8 inches.

OBSERVATIONS AND MY LATEST THOUGHTS:
A weak cold front is progressing southeastward across the Austin metro area at 1pm today with
the front just passing Camp Mabry where their temperature has fallen 7 or 8 degrees in the last
hour. Temperatures ahead of the front are in the low 70s with temperatures falling into the 50s to
low 60s immediately behind the front. This front is expected to become the focus for rain shower and
thunderstorm activity in the next few hours with the approach of the upper level low over northwestern
Mexico.

NWS Doppler weather radar shows eastward moving rain shower and thunderstorm activity becoming
more widespread over the northwestern Texas hill country. Rain showers are also developing along
the cold front over our metro area as well as to the south of the area.. those precipitation elements are
moving northward.

Widespread rain showers and thunderstorms are expected by later this afternoon and continuing
through tonight and through the day Saturday with generalized 3 to 4 inch rainfall totals with isolated
heavier totals possible as noted by NWS/Austin-San Antonio.

No flooding is indicated anywhere in the area as of 1pm today.

Given the ongoing threat of heavier rainfall as well as the possibility of flooding tonight into Saturday,
all interests throughout south central Texas should remain weather aware and listen for the latest
information from the NWS/Austin-San Antonio as well as local emergency management officials.

Have your NOAA/NWS All Hazards Weather Radios reset and ready to alarm in case the
NWS/Austin-San Antonio issues additional advisories and warnings over the next 48 hours.

The LCRA Hydromet is a great way to keep informed of ground truth precipitation amounts…
http://hydromet.lcra.org/full.aspx

The City of Austin Watershed Protection website… www.atxfloods.com … is a great way to keep
track of flooded low water crossings throughout the area.

I’ll continue to monitor the weather situation..

tk

TK’s Audio Weather Webcast…. (955am CT-Fri/20Mar2015)

by troyk | on Mar 20, 2015 | Comments Off

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TK’s Austin and South Central Texas Weather Forecast….

by troyk | on Mar 20, 2015 | Comments Off

Updated 845am CT.. Friday / 20 March 2015

…. NWS/Flash Flood Watch 1pm Today Through 7pm Saturday ….

TODAY…. Cloudy and turning a little cooler as a cold front passes. Rain showers and a few thunderstorms spreading across the area by afternoon. Periods of heavier rain possible by late in the afternoon. Rainfall, given an 70% chance of rain at any given location, will average 1/2 inch. High 70.Southerly wind shifting north northwesterly 5 to 12 mph.

TONIGHT…. Cloudy with rain showers and a few thunderstorms. Periods of heavy rainfall possible with associated flooding problems. Rainfall, given a 100% chance of rain at any given location, will average 1 to 2 inches or more. Low 56. Northerly wind 5 to 10 mph.

SATURDAY…. Mostly cloudy with rain showers and a few thunderstorms. Periods of heavy rainfall possible with associated flooding problems. Rainfall, where it occurs given a 100% chance of rain at any given location, will average 1 to 2 inches or more. High 65. Northeasterly wind 5 to 10 mph.

SATURDAY NIGHT…. Mostly cloudy with scattered rain showers. Rainfall, where it occurs given a 60% chance of rain at any given location, will average 1/4 inch. Low 53. Light easterly wind.

SUNDAY…. Widely scattered rain showers in the morning.. otherwise decreasing clouds becoming partly cloudy in the afternoon. Morning rainfall, where it occurs given a 20% chance of rain at any given location, will average 1/10th inch or less. High 69. East southeasterly wind 5 to 10 mph.

SUNDAY NIGHT…. Partly cloudy. Low 52. Light easterly wind.

MONDAY…. Mostly sunny. High 71. Light south southeasterly wind.

MONDAY NIGHT…. Mostly clear. Low 54. South southeasterly wind 4 to 8 mph.

TUESDAY…. Partly cloudy. High 73. Southerly wind 5 to 10 mph.

TUESDAY NIGHT…. Partly cloudy. Low 56. South southeasterly wind 4 to 8 mph.

WEDNESDAY…. Partly cloudy. High 76. Southerly wind 8 to 15 mph.

WEDNESDAY NIGHT…. Partly to mostly cloudy with Isolated rain showers and thunderstorms as a cold front approaches after midnight. Rainfall, where it occurs given a 10% chance of rain at any given location, will average 1/4 inch or less. Low 59. Southerly wind 5 to 12 mph.

THURSDAY…. Partly to mostly cloudy and a little cooler as a cold front passes around daybreak. Widely scattered rain showers and thunderstorms. Rainfall, where it occurs given a 20% chance of rain at any given location, will average 1/4 inch or less. High 70. Winds becoming northerly wind 5 to 12 mph.

NATIONAL WEATHER SERVICE / 8 TO 14 DAY OUTLOOK
Valid Friday / 27 March 2015 through Thursday / 02 April 2015…
Temperature… Below Average
Precipitation… Below Average

AUSTIN SUNSET/SUNRISE TIMES…..
Sunrise this morning (20 March)…………………………………………. 7:34 am
Sunset this evening (20 March)…………………………………………… 7:43 pm
Sunrise Saturday (21 March)………………………………………………. 7:33 am
Sunset Saturday (21 March)……………………………………………….. 7:43 pm

TK’s Weather Discussion….

by troyk | on Mar 20, 2015 | Comments Off

Updated 915am CT – Friday / 20 March 2015

.. Strong Upper Level Low Pressure To Pass Overhead Tonight Through Saturday ..
.. Three Inches or More of Rainfall Possible Today through Saturday Night ..
.. Flash Flood Watch in Effect From 1pm Today Through 7pm Saturday ..

On this Friday morning…. a southeastward moving cold front is moving southeastward through our area this morning. As a result of this surface weather pattern, our local surface winds are becoming northerly as the front moves south.

In the upper levels of the atmosphere.. a strong upper level low pressure disturbance is located over western and northwestern Mexico. As a result, our upper air winds at about 18,500 feet are southwesterly at 45 to 55 mph.

The strong upper level disturbance.. to our distant west.. will be approaching the area by tonight with it moving overhead tomorrow and tomorrow night with abundant atmospheric moisture in place across the area. The approaching upper level storm will combine with the cold front to result in widespread rain and even thunderstorms through Saturday into Saturday night.

Given colder temperatures aloft and the resulting atmospheric instability, there will be some embedded thunderstorms as the system passes. Forecast precipitation amounts.. in both the manual NWS guidance as well as the atmospheric model output.. have increased with upwards of 3 inches or more of rain possible through Saturday and Saturday night. NWS Austin-San Antonio meteorologists are suggesting that some isolated spots may see as much as 6 to 8 inches of rain. They have already revised the Flash Flood Watch to go into effect at 1pm today and continue through 7pm Saturday evening. Make no mistake… where 3 to 8 inches of rain occurs, there will be flooding problems. Local interests throughout south central Texas.. especially with numerous events going on around the area.. are strongly encouraged to monitor the latest information regarding this potential heavy rain/flood event for tomorrow into the upcoming weekend. Over the coming days, it will likely pay to remember the NWS Sloan as it regarding flooding.. “Turn Around, Don’t Drown.”

As the upper level low pressure moves northeastward out of the area and the cold front moves further southeast, we’ll see rain chances decrease by late Saturday night and early Sunday morning. Clouds will break a bit by Sunday afternoon.

A drier and more stable weather pattern.. with a warming trend.. will prevail for the first half of next week.

Another cold front is slated to move southeastward through the area with a slim chance of rain and thunderstorms by daybreak next Thursday.

Regarding my forecast, my local forecast confidence: My forecast confidence is medium to high through the weekend. The main questions will be the precipitation timing and amounts as well as flash flood potential. My forecast confidence rises back to high to very high for the first half of next week with my confidence falling again (reference rain chances) by next Wednesday into Thursday as the next cold front approaches and moves through the area.

Have a good Friday….
Meteorologist Troy Kimmel

Contact me:
tkimmel@austin.utexas.edu

http://www.facebook.com/troykimmel

…. NWS Issued Flash Flood Watch Begins at 1pm Today ….

by troyk | on Mar 20, 2015 | Comments Off

Austin / Travis County and South Central Texas Weather Statement #2
Prepared by UT University/Incident Meteorologist Troy Kimmel
800am CT – Friday / 20 March 2015


.. Upper Level Low Pressure Storm System Moves Overhead Through Saturday Night..
.. Three or More Inches of Rainfall Possible Today through Saturday Night ..
.. NWS Austin-San Antonio has, Before Becoming Effective, Redefined the Time of Flash
Flood Watch For All of the Local Area
Effective 1pm Today (Instead of 4pm) through
7pm Saturday
..

On this Friday morning…. a cold front is moving southeastward from south of Tyler to south
of Waco to south of Junction. In the upper levels of the atmosphere.. a strong upper level
low pressure disturbance is located over northwestern Mexico.

The strong upper level disturbance.. to our distant west.. will be approaching the area by later
today into tonight and through Saturday with abundant atmospheric moisture in place across
the area. The approaching upper level storm will combine with the advancing cold front to
create abundant atmospheric lift resulting in widespread rain and even thunderstorm activity by this
afternoon into Saturday night and early Sunday.

As mentioned, above, given cooler temperatures aloft/atmospheric instability, there will be some
embedded thunderstorms as the system passes. As seen below (first map).. forecast precipitation
amounts, in both the manual NWS national guidance as well as the atmospheric model output..
continue with upwards of 3 or more inches of rain possible from now through Saturday night and
until 7am Sunday. Reference the second and third maps below, the NWS Weather Prediction
Center in Washington has all of our area in a “slight” risk area for exceeding flash flood values
7am today through 7am Sunday.

http://www.hpc.ncep.noaa.gov/qpf/d12_wbg.gif
http://www.hpc.ncep.noaa.gov/qpf/94ewbg.gif
http://www.hpc.ncep.noaa.gov/qpf/98ewbg.gif

NWS Austin-San Antonio meteorologists.. who had already issued, at mid morning yesterday, a
FLASH FLOOD WATCH to be effective at 4pm today for all of our area..  have already revised
that watch to become effective at 1pm today with an earlier onset of heavier precipitation expected.
As originally issued, the watch will be valid until 7pm Saturday. They continue to suggest that some
isolated spots may see as much as 6 to 8 inches of rain. Make no mistake… rainfall amounts of 3 to
8 inches will cause flooding issues across the area. Local interests throughout south central Texas..
especially with numerous events going on around the area.. are strongly encouraged to monitor the
latest information regarding this potential heavy rain/flood event for tomorrow into the upcoming
weekend. As we make our way through the next several days, it’ll likely pay to remember the NWS
Slogan… “Turn Around.. Don’t Drown.”

Another factor, as the upper level low pressure area approaches the area today, the front to our
immediate north will surge southeastward across the area resulting in cooler temperatures beginning
later this afternoon into the weekend.

After rain chances decrease Saturday night into early Sunday, clouds will break a bit Sunday into
Monday.

I will continue to monitor this situation.
tk