Texas Spring 2017

[bubba hotep]

The NAMs would be a train wreck for the DFW area, basically nothing from this next system in the way of rain.

I wouldn't worry about it yet. The BMJ convective scheme used by the NAM often struggles to properly convect in dry mid-level environments.

From the MetEd module:

Models: The BMJ scheme is used in the operational NCEP NAM Model and some members in the NCEP Short Range Ensemble Forecast system.

Convective Process

Trigger: Three conditions are required to trigger convection:

At least some CAPE
Convective cloud depth exceeding a threshold value
Moist soundings to activate

Yeah, it was just an observation and not a concern. I'm more interested in seeing what the 00z NCAR ensembles do tonight than anything else, they hint at there being some kind of a weak trigger along the dryline SW of DFW tomorrow. That could be big time trouble, given the setup. However, I skeptical that anything will be able to break the cap tomorrow.

[bubba hotep]

12z Euro is another uptick in rainfall totals. If this trend continues then the flash flood watch may need to be expanded southward into NE Texas.

[1900hurricane]

The ECMWF has repeatedly fired convection on what appears to be some sort of weak effective warm front or some other gradient boundary in ESE Texas (from about Beaumont to Crockett) Saturday afternoon. I'm not really sure why it's there and where it comes from, but it has been a consistent feature for the past few runs. If something like that were to transpire, that could be something that enhances otherwise largely uniderectional shear, which is always concerning in the presence of CAPE of that magnitude. It'll be interesting to see if that feature remains persistent and/or if other guidance (such as the CAMs one they're in range) begin to pick it up as time progresses.

[weatherdude1108]

EWX discussion. We're going bowling Saturday evening with some friends from 5:30 to 8:30pm. Hopefully the storms can hold off until after that time.


Area Forecast Discussion
National Weather Service Austin/San Antonio TX
245 PM CDT Thu Apr 27 2017

.SHORT TERM (Tonight through Friday Night)...
Low level moisture will return tonight with stratus developing
overnight. Friday morning lows will be around 15-20 degrees warmer in
some areas compared to this morning. Low level moisture will continue
to increase Friday and Friday night beneath a strengthening cap and a
few isolated showers may be possible Friday night into Saturday
morning. Breaks in the cloud cover Friday afternoon should allow
temperatures to climb into the low 90s across the east and mid 90s
across the south and west. Combined with increasing dew points this
should put heat index values into the upper 90s across the region
tomorrow afternoon.

&&

.LONG TERM (Saturday through Thursday)...
An upper level low through the short term will develop near the Four
Corners and Southern Rockies and by Saturday morning be located
across New Mexico. A lead shortwave in the southwest flow aloft will
move through eastern areas of the CWA during the day on Saturday.
The main question will be how quickly the cap erodes during the day
on Saturday, if it completely erode at all. As has been the case
much of the Spring, GFS forecast soundings at AUS and SAT indicate a
much faster erosion of the cap than does the ECMWF, Canadian and
NAM12 and as such develops isolated/scattered convection near and
east of I-35 Saturday afternoon. Am leaning towards a slightly
stronger cap as the rest of the model soundings indicate and slower
erosion during the day on Saturday, awaiting for the main forcing
Saturday night. However, if a storm were to develop MUCAPE values of
3000-3500 J/KG combined with 0-6km shear values of 40-50 kts could
yield an isolated strong to severe storm Saturday afternoon.

As mentioned the main forcing in the base of the upper level low
moving into Texas will eventually lead to better chances of storms as
the associated cold front catches up with the dry line over the CWA
early Saturday evening. This should help convection overcome what is
left of the weakening cap through portions of the Hill Country and
I-35 corridor between 00Z-03Z Saturday evening. Eventually storms
could organize into a broken line as the front progresses east of
I-35 late Saturday evening and into the overnight. Given the
aforementioned MUCAPE and increasing 0-6km shear values over the
region, there will be a risk for some storms Saturday night to be
severe across portions of the Hill Country and along and east of
I-35. The main threats at this time appear to large hail initially,
transitioning to damaging straight-line winds east of I-35 should a
line develop. 0-1km and 0-3km shear will be low and does not align
well with the most unstable area, therefore the potential for
tornadoes associated with this activity appears low at this time.
While pockets of heavy rain may occur, the progressive nature of the
front will sweep the entire system through quickly by Sunday morning
limiting the potential for a widespread flash flood threat. Overall
rainfall totals 1/4 to 1 inch will be common across central and
eastern areas, with pockets up to 2 inches possible.

Clearing with windy northwest winds developing during the day on
Sunday. This could lead to elevated to near critical fire weather
conditions Sunday afternoon across western areas that do not receive
much rain with this system.

Below normal lows will occur again on Monday morning behind the
front, with lows into the upper 40s and low 50s in many areas. A
warming trend will take place Monday afternoon through Wednesday.
Another potential upper level system and surface cold front looks to
possibly impact the area Wednesday and Wednesday night. There is
currently a large spread between the ECMWF and GFS on timing of this
cold front.

[Brent]

DFW missed the record low by 2 degrees and looks to be largely below normal for at least the first week of May(even the warmest days may struggle to make 80 which is average).

Sunday and again next Thursday could be anomaously chilly.

What month is it again?

[bubba hotep]

Wow... 3k NAM is showing 5,500+ CAPE across N. Texas tomorrow. If a storm could get going?! The dryline circulation looks like it could be deep enough but the dryline isn't very sharp, so there might not be enough convergence along it.

[1900hurricane]

The ECMWF has repeatedly fired convection on what appears to be some sort of weak effective warm front or some other gradient boundary in ESE Texas (from about Beaumont to Crockett) Saturday afternoon. I'm not really sure why it's there and where it comes from, but it has been a consistent feature for the past few runs. If something like that were to transpire, that could be something that enhances otherwise largely uniderectional shear, which is always concerning in the presence of CAPE of that magnitude. It'll be interesting to see if that feature remains persistent and/or if other guidance (such as the CAMs one they're in range) begin to pick it up as time progresses.

The 00Z 3 km NAM looks like it it trying to do something similar now as well, backing surface winds across much of SE TX and enhancing low level shear. Coupled with the huge CAPE present, this is leading to some impressive derived parameters.

[Tireman4]

000
FXUS64 KHGX 281121
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
621 AM CDT Fri Apr 28 2017

.AVIATION...
Main issues this morning will be timing of the MVFR conditions
lifting to VFR and an increase in the wind speeds. Should see
winds increasing before or as the ceilings lift. Patchy fog or
haze possible at the coast. During the late morning and afternoon
winds will become gusty. Tonight the winds will stay up even as
the ceilings once again lower to MVFR. At the coast and near
Galveston Bay winds may gust to 25 to 30 knots. Overnight tonight
wind gusts to near 34 knots are possible at KGLS.

40

&&

.PREV DISCUSSION... /ISSUED 408 AM CDT Fri Apr 28 2017/

DISCUSSION...
At 100 AM, an area of low pressure was located over west Texas
with a dry line extending from about Lubbock to Ft Stockton. The
pressure gradient across east Texas was tightening in response to
the deepening area of low pressure out west. South winds will
strengthen throughout the day and breezy conditions will prevail
by afternoon. High temperatures today are conditional on when the
clouds break and the amount of mixing produced by sfc winds. 850
temps are progged to reach 25 C this afternoon and bringing these
values down to the sfc dry adiabatically will produce sfc temps
between 98-100. Clouds for the first half of the day should moderate
temps a bit but once sunshine returns in the aftn, feel temps could
rise pretty quick. Heat index values will climb today and will
probably top out in the upper 90s this afternoon. It will feel
more like summer today. Min temps tonight should remain very warm
with clouds filling back in during the evening to help insulate.
Winds will remain strong so mixing will also keep temps from
falling much. Would not be surprised if a few locations remained
near or above 80 degrees overnight.

The strong winds will also produce elevated tides late tonight. Water
levels could reach values between 3.5 and 4.0 feet and this would produce
some flooding along the coast, especially along the Bolivar peninsula. A
coastal flood watch has been issued for late tonight through
Saturday with the best window for coastal flooding around sunrise
Saturday.

Saturday will remain warm with high temps warming into the
mid/upper 80s. Could get a few showers beneath a strong capping
inversion Saturday morning as the low level jet nears the
area. There could be some aftn convection as strong capping in
the morning gradually weakens, PW values climb to 1.90 inches and
convective temps drop into the mid 80`s.

Strong thunderstorms are expected to move across SE TX Saturday
night. SPC has outlooked much of the region in Slight or Enhanced
Risk for Saturday night. CAPE values will 3000 J/Kg, LI values
between -9 and -11, lapse rates around 7.0 C and helicity values
between 180 and 300 m2/s2. Jet structure shows a nice split in the
winds at 300 mb so it appears all the parameters are in place for
a severe weather event Saturday night. So what could go wrong?
Fcst soundings show a very strong capping inversion that just
vanishes as a cold front and upper level dynamics approach. Not
sure the cap will erode as the models suggest, especially over the
southern half of the region. Took a look back at the CIPS analog
page and previous events with this type of weather pattern only
showed a few severe weather reports over the extreme northern
parts of SE TX. There is still a great bit of uncertainty how this
weather event will unfold so keep up with the forecasts. The cold
front will still trigger a line of shra/tsra Saturday night and
the CIPS page showed about 0.50 to 1.00 inch of rain with past
events. Most of the area should receive some rain with the
heavier totals to the north.

Rain should end around sunrise Sunday morning with skies clearing
by afternoon. High temps will trend cooler with max values in the
mid/upper 70s. Dry conditions will prevail Monday but moisture
levels begin to increase on Tuesday and a few showers will be
possible by Tuesday night as an upper level trough approaches
from the west. The trough coupled with a sfc cold front will bring
the area a good chance of showers and thunderstorms on Wednesday.
Fcst soundings again show some potential for strong storms with
CAPE values above 3500, steep lapse rates and LI values around
-10. Clearing conditions and cooler temperatures are expected in
the wake of the front for Thursday and Friday.

MARINE...
Winds over the bays and Gulf waters are expected to pick up and will
probably reach caution criteria toward sunrise. The big event will
then set up later with advisory conditions expected by sunset. Gusts
to gale force are likely over the Gulf waters later tonight through
at least early Sunday. Winds should diminish as a cold front
approaches the coastline. The result of the strong winds will be
long-period swells and high surf. Forecast models indicate the
possibility of water levels reach over 3.8 feet at Pleasure Pier on
Galveston Island and over 3.5 feet at Freeport. Because of the
potential, have issued a coastal flood watch for overnight tonight
through mid afternoon Saturday.

40

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 90 77 87 57 74 / 10 20 40 80 10
Houston (IAH) 90 78 87 64 76 / 10 20 30 80 30
Galveston (GLS) 84 79 83 68 77 / 10 20 20 80 60

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Coastal Flood Watch from late tonight through Saturday afternoon
for the following zones: Brazoria...Chambers...Galveston...
Matagorda.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION through this evening 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...Galveston Bay...Matagorda
Bay...Waters from Freeport to the Matagorda Ship Channel
from 20 to 60 NM...Waters from High Island to Freeport from
20 to 60 NM.

Small Craft Advisory from 7 PM this evening to 2 PM CDT Sunday
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...Waters from Freeport to
the Matagorda Ship Channel from 20 to 60 NM...Waters from
High Island to Freeport from 20 to 60 NM.

&&

$$

Discussion...43
Aviation/Marine...40

[bubba hotep]

As expected, big cap in place on the 12z FWD sounding. It still looks like areas east of I35 in DFW will pick a good soaking this weekend. Now, on to something more interesting, holy cow the latest Euro Weeklies! Below and above for basically all of Texas. If it verified, it would be a major paradigm shift from the past few years of basically constantly above normal temps.

[DonWrk]

GFS constantly having a big storm at the end of the entire run for the past few days now. Even if it doesn't verify I'd much rather see wet days than it showing dryness.

[bubba hotep]

The Texas Tech 3k WRF shows some cells firing across DFW tomorrow ahead of the front. Could be an issue if something like that does occur and the cells are surface based.

[JDawg512]

Yet another system that may or may not give me rain. Depending on which model, either i'll have a quick line move through or will be just south of the southern tip of the line missing out completely.

[Portastorm]

Yet another system that may or may not give me rain. Depending on which model, either i'll have a quick line move through or will be just south of the southern tip of the line missing out completely.

May I ask what you are looking at? I have not seen one model which shows Austin getting zero rain. The worst I have seen is the GFS which shows about 3/4" of an inch. The new Euro (12z) shows anywhere from 1.5-2.0" of rain for Travis County by Monday.

[weatherdude1108]

Bob Rose's take as of 2:40pm today:

[b]Forecasters are closely following a trough of low pressure in the middle and upper atmosphere that was located Friday over the Four Corners region. The trough is forecast to track to east tonight and Saturday, turning northeast across the Texas and Oklahoma on Sunday. The advancing trough will help push a cold front southeast across Texas Saturday into Saturday night, and is expected to cause the weather pattern to become fairly active.

Ahead of the cold front Saturday, moisture will be increasing off the Gulf of Mexico, causing the sky to remain mostly cloudy. The atmosphere is forecast to become increasingly moist and unstable by Saturday afternoon. A few spotty rain showers will be possible across the region Saturday morning, followed by an increasing chance for scattered rain showers and thunderstorms Saturday afternoon. The probability for rain Saturday afternoon will be near 40-50 percent across the Hill Country and Central Texas regions and near 20 percent across the coastal plains. A few of the thunderstorms could become strong to severe, producing large hail and damaging winds. Saturday's temperature is forecast to reach the upper 80s.

An elongated area of rain showers and thunderstorms is forecast to develop along the cold front late Saturday afternoon into Saturday evening as the front pushes southeast from West Texas into the Hill Country. The front and its accompanying rain and storms is forecast to reach the Austin/Interstate 35 corridor region early to mid-Saturday evening, moving across the rest of Central Texas late Saturday evening. The rain and storms should spread across the coastal plains region shortly after midnight Saturday night. An area of light to moderate rain is forecast to continue shortly behind the cold front. The rain should end from west to east late Saturday night toward daybreak Sunday.

Some of the thunderstorms along the cold front may also become severe, producing large hail and damaging downburst winds. The Storm Prediction Center has placed the eastern Hill Country and all of Central Texas under a Slight Risk for severe thunderstorms from 7 am Saturday through 7 am Sunday. Areas east and northeast of Austin, including Lee County and eastern Williamson County have been placed under an enhanced risk for severe storms during this period.[/b]

Rain totals Saturday through Sunday morning are forecast to be heaviest across the eastern Hill Country and along the Interstate 35 corridor. National Weather Service forecasts suggest this area could see totals of 1-1.25 inches. Totals to near a half inch are forecast across most of the Hill Country and the middle Texas coast.


http://www.lcra.org/water/river-and-wea ... ather.aspx

[Ntxw]

Meanwhile 2-6" of snow forecasted for the panhandle especially northwestern parts. Even more in Kansas, NM, and CO.

[weatherdude1108]

Meanwhile 2-6" of snow forecasted for the panhandle especially northwestern parts. Even more in Kansas, NM, and CO.

That's just crazy. The Winter we didn't have.

[weatherdude1108]

Our bowling ends at 8:30pm Saturday. They're talking the storms hitting the I35 corridor between 8pm and midnight Saturday. Not for certain, but ugh. I may be looking for the nearest gas station/overpass to take shelter from the hail if it comes to fruition, especially since I will be with my family.

EWX:

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
246 PM CDT Fri Apr 28 2017

.SHORT TERM (Tonight through Saturday Night)...
Warm and humid across South Central Texas this afternoon. The center
of the upper level low near the Four Corners this afternoon will dig
southeast through New Mexico tonight and Saturday then east through
the Panhandle Saturday night. Stratus will re-develop late this
evening beneath a developing cap. Beneath the cap a few showers will
be possible by Saturday morning across the eastern half of the CWA.
The main question continues to be how much the cap will erode during
the day on Saturday. As continues to be the case, GFS point forecast
soundings completely erode the cap along and east of the I-35 corridor
Saturday afternoon. We continue to lean towards a slightly stronger
cap this far south as the rest of the models indicate and slower
erosion during the day on Saturday, awaiting for the main forcing
Saturday night. However, if a storm were to develop Saturday
afternoon steep mid level lapse yielding very high MUCAPE values of
3500-4500 J/KG combined with 0-6km shear values of 40-50 kts could
produce an isolated severe storm Saturday afternoon.

The greatest chance of strong to severe thunderstorms continues to
be Saturday night, as the cold front catching up to the dry line over
the area and PVA and cooling in the base of the trough overcome the
cap. It appears storms will develop southward into portions of the
Hill Country and I-35 corridor between 8 PM and midnight and east of
the I-35 corridor between 10 PM and 2 AM. Given the aforementioned
CAPE values pooled ahead of the front over the area and increasing
deep layer shear values to 50-60 kts large hail appears to be at
least equal if not slightly greater than the damaging wind threat for
the duration of the event. A much lower, but non-zero, threat for an
isolated tornado exists across the northeast CWA.

The are some indications in some of the hi resolution models
guidance that the cold front could race eastward east of I-35 and
undercut some of the deeper convection after midnight. However for
now SPC Day 2 Convection Outlook continues portions of the CWA near
and north of I-10 in a Slight Risk for severe storms, with portions
of the far northeast CWA in an Enhanced Risk. Have added mention of
severe into the forecast for this general area Saturday night.

Due to the progressive nature of this system rainfall amounts across
the central and eastern CWA look to average 1/4 to 1 inch limiting
any potential for widespread flooding concerns. Isolated pockets of
1-2 inches can not be completely ruled out north of I-10. Farther
west toward the Rio Grande rainfall amounts drop off to nothing.

&&

.LONG TERM (Sunday through Friday)...
Clearing with windy northwest winds developing during the day on
Sunday. This could lead to elevated to near critical fire weather
conditions Sunday afternoon across western areas that do not receive
much rain with this system.

Below normal lows will occur again on Monday morning behind the
front, with lows into the upper 40s and low 50s in many areas. A
warming trend will take place Monday afternoon through Wednesday.
Another upper level system and surface cold front looks to impact
the area Wednesday and Wednesday night. ECMWF continues to be slightly
more progressive than the GFS with the main chance for rain coming
with the front during the day on Wednesday while the GFS is indicating
Wednesday night. Cooler with below normal temperatures behind this
second front.

[JDawg512]

Yet another system that may or may not give me rain. Depending on which model, either i'll have a quick line move through or will be just south of the southern tip of the line missing out completely.

May I ask what you are looking at? I have not seen one model which shows Austin getting zero rain. The worst I have seen is the GFS which shows about 3/4" of an inch. The new Euro (12z) shows anywhere from 1.5-2.0" of rain for Travis County by Monday.

The Tropical tidbits site in the mesoscale section. The 3K Nam shows just a skinny little line come through, though I having checked the most recent update. The WRF-ARW looks the best. If you have suggestions for other sites where I can view models please let me know. As far as Euro goes, don't have access to it. Call me jaded since a lot of rain missed my imediate area this month. I may be overly pessimistic (and believe me I'd rather not), but for now going by recent events I'm not keeping my hopes up too much.

[gboudx]

Meanwhile 2-6" of snow forecasted for the panhandle especially northwestern parts. Even more in Kansas, NM, and CO.

We were in Colorado Springs last weekend and saw some flakes of snow. Good thing our trip wasn't this weekend. My wife hates the cold and wasn't thrilled with the few flakes of snow. I'd be divorced if we were there this weekend instead. They have WSW for 4-8" of snow, more in the mountains.

[TexasF6]

Austin is in the enhanced risk, just as I thought we would be by a look at the sky late yesterday....Be safe folks!!!