March-2017: Active Spring WX Pattern Ahead

[srainhoutx]

Two very impressive mesocyclones ( Super Cells ) impacting Baytown/Mont Belvieu and another near Woodville.

[srainhoutx]

HGX: Numerous ship cargo containers moved and dropped in Barbours Cut. EMS transporting two patients at this time. Tornado possible.

[Katdaddy]

The active pattern with the parade of storm systems continues as the severe weather threat progresses into the MS Valley down to the Gulf Coast and across SE US today.

Beautiful weather across much of TX for today and Friday with partly to mostly sunny skies. Slightly cooler temps with highs in the upper 70s across SE TX.

The next storm system will bring an increasing severe weather threat to the Central and S Plains down to the Middle and Upper TX Coast Saturday afternoon and night. This threat spreads into SE TX, E TX, and much of LA on Sunday. The potential will also exist for heavy rains leading to a flooding concern for SE TX.

[srainhoutx]

Thursday morning briefing from Jeff and storm reports from yesterday:

Another powerful upper level storm system to impact the area this weekend.

The upper level system which brought severe weather and flooding to the area yesterday is progressing eastward this morning while the next system to cause impacts to our area is approaching the US west coast. Air mass has dried and cooled behind a weak cold front which passed through the area overnight and this air mass will be in place today into early Friday. Winds will return to the SSE by midday Friday and the return of Gulf moisture will be underway ahead of the next approaching storm system.

Saturday:
Moisture returns in earnest on Saturday with PWS rising to above normal levels. Upper level system will begin to approach W TX and a short wave will move across NC TX during the afternoon hours. Latest models are showing more and more development of showers and thunderstorms Saturday afternoon and evening as lift combines with the ongoing warm air advection regime. Do not expect any severe weather late Saturday into Saturday night, but rainfall could be heavy at times.

Sunday:
Brunt on main lift and highest moisture levels come to bear across the region…for an active weather day! While parameters are a little vague at this range, enough support is in the global model guidance for both a severe and heavy rainfall threat on Sunday. Strong upper air disturbances will move into N MX/SW TX late Saturday night into Sunday morning helping to ignite widespread thunderstorm development over SW TX, SC TX, and the coastal plains by early Sunday morning. Storms may grow upscale into a slow eastward moving MCS which will then impact SE TX from the morning into the afternoon hours on Sunday. Upper air winds will favor cell training of potentially excessive rainfall rates (2-4 inches per hour) which can quickly cause problems in urban areas. The severe threat at this time is more conditional and likely second to the heavy rainfall threat given questions on available instability and how meso scale processes may evolve. Think all severe modes will be possible similar to yesterday, but not confident on the threat level at this point.

Given recent heavy rainfall yesterday and a very short return period for additional heavy rainfall the threat for flash flooding/flooding will be higher with this incoming system. Ground conditions are saturated after yesterday and will only dry slightly before the onset of additional heavy rainfall. Other concerns include the potential for saturating rainfall Saturday evening before the main round of thunderstorms on Sunday and the potential for high hourly rainfall rates.

Wednesday Storm Reports:

Houston, Harris: ***1 injured*** Construction worker on a roof in SW Houston was struck by lightning. Co-workers performed CPR until paramedics arrived and were able to revive the individual.

Addicks, Harris: Lightning struck as house resulting in significant fire damage

Bellaire, Harris: ***Tornado*** EF-1 tornado confirmed by NWS assessment team at the Azalea Place apartment complex. Tornado was 50 yards wide and .25 of a mile long. Roof, tree, and carport damage at the apartment complex. Estimated wind speed 90mph

Bellaire, Harris: trees down at Braewick and Braeswood

Bellaire, Harris: Large trees down on Holly Hall near New Castle

Jersey Village, Harris: dime size hail at the intersection of US 290 and Fairbanks N Houston

Lake Houston, Harris: half inch diameter hail reported at Lake Houston Dam

Friendswood, Galveston: Flash flooding from excessive rainfall trapped several vehicles in high water

Baytown, Harris: Flash Flooding from excessive rainfall resulted in deep street flooding. One person on a bicycle fell into a storm drainage culvert and was sucked into the culvert by the flow of the water. Nearby motorists pulled the person out of the culvert saving their life

Pasadena, Harris: ***Tornado*** Significant roof damage at a large warehouse on Bay Park Rd. Cars in the parking lots overturned. Cell video showed a tornado approaching the location. NWS will survey and rate damage today.

La Porte, Harris: ***Tornado, 2 Injured*** Numerous large shipping containers moved, lofted, and dropped at Barbers Cut Terminal…2 persons were injured when containers struck them. Several cars were lofted and moved with a few overturned. This is likely the same tornado that struck the Pasadena area and NWS teams will visit the area today to determine where this was one continuous path or two separate touchdowns.

Cove, Chambers: North Point Weatherflow Station measured wind gust of 48mph

Cove, Chambers: Flash flooding stalled vehicles at I-10 and FM 565

Morgan’s Point, Harris: 55mph measured at Morgan’s Point

[Katdaddy]

A beautiful and cool morning across SE TX will transition to a beautiful hot afternoon with highs in the mid to upper 80s. Saturday will be a transition day with increasing GOM moisture and strong gusting S winds ahead of potentially significant severe weather event for SE TX with all modes of severe weather possible including flooding from late Saturday through Sunday night. The event will begin Saturday afternoon across Central TX and progress ESE across TX through Sunday night. More updates this weekend but you need to be weather aware from Saturday evening through Sunday night.

[Andrew]

Definitely keep an eye out for Sunday's event, some impressive parameters could come together for Southeast Texas. Haven't seen a setup like this in a while.

[tireman4]

Alluding to what Andrew stated, the NWS AFD this morning. Be weather wary Sunday folks...

000
FXUS64 KHGX 311101
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
601 AM CDT Fri Mar 31 2017

.AVIATION [12Z TAF Issuance]...

Mostly straightforward forecast, with most/all sites at VFR
ceilings and visibilities for most/all of their period. Could see
fog or low stratus later tonight, but have only sketched at things
since onset appears to be towards the end of the period as a dry
atmosphere needs to be overcome first.

Beyond cigs/vsbys, southerly onshore flow will establish itself
and become stronger through the day. Eventually think things will
settle in around 10 knots, but gustier in the afternoon. With
sundown, gusts should settle with a bit of a reduction in
sustained winds as well.

Luchs

&&

.PREV DISCUSSION /Issued 444 AM CDT Fri Mar 31 2017/...



.SHORT TERM [Today and Tonight]...

Bodies of water - even small lakes - are clearly visible on IR
satellite late tonight, highlighting the clear skies and light
winds to allow for good radiational cooling. Observations show
that most locations are in the low to mid 60s, with a few rural
spots dropping into the 50s. Conroe is a cool "extreme" at 52.

Expect all but the immediate Gulf coast to slip into the 50s by
morning given dewpoints in the mid 40s to lower 50s. Sunny skies
should prevail most of the day, helping temperatures soar, aided by
warm southerly onshore flow becoming reestablished as surface high
pressure drifts eastward and low pressure begins to form up on the
Texas/New Mexico border.

Low temperatures tonight will be considerably warmer as onshore flow
only continues to fuel a warm, moist profile at the surface. With
dewpoints much higher, may be on the lookout for fog. But, a
tightening pressure gradient should also spur stronger winds, and so
at this time the forecast goes for low stratus instead of fog.

Luchs


.LONG TERM [Saturday Through Friday]...

Sunday...
All I will say about Saturday is to get out and enjoy it. High
temperatures will be in the 80s with moisture return from the
Gulf. Beginning as early as 06Z Sunday through about 00Z Monday,
SE Texas will need to monitor weather closely. SPC has an enhanced
severe weather risk for all of the area on Sunday. WPC has areas
north of a Brenham to Humble line in a slight risk for excessive
rainfall. This means up to a 10 percent chance of exceeding flash
flood guidance. Bottom line being impacts from all weather hazards
may be possible - hail, damaging wind, tornadoes and flooding.

Current water vapor imagery quite clearly shows an upper level
low over the Great Basin into the Desert SW. This system should
reach El Paso by 12Z Sunday. Synopticly this deep trough will
have a strong jet streak moving out of Mexico into Texas during
the day with a vorticity maximum swinging across Mexico into C
Texas by Sunday evening. Large scale lift will be enough to limit
capping from the elevated mixed layer except for maybe south
Texas. A temperature gradient at 850mb may set up from central
Texas northeast towards the Arklatex. It is along this gradient
that both the GFS/ECMWF develop quite a bit of precipitation
meaning areas from Caldwell to Crockett could stand to see heavy
rainfall and flooding potential. These details will likely change
with future model runs but something to monitor with future runs.
There will be about 1.6-1.9 inches of precipitable water, broad
large scale lift from the trough and for good measure 40-50kt LLJ
oriented normal to this 850mb temperature gradient. This
environment very much supports heavy rainfall thus WPC slight risk
of excessive rainfall for areas north of Brenham to Humble.

The environment also is quite favorable for severe weather as
highlighted by SPC`s day 3 outlook. Again these details will
likely change but for now both the GFS/NAM support deep moisture
through the boundary layer. Model soundings for each show moisture
through at least 800mb and surface dewpoints in the upper 60s to
possibly low 70s. Instability is quite high given the set up with
CAPE more than 2000 J/kg mainly due to steep lapse rates (which
would support severe hail). Warm advection and large scale lift
should be enough for surface based convection to form in the warm
sector and even along warm front/850mb temp gradient outlined
above. As for shear, 45-50kts of 0-6km bulk shear and 20-30kts of
0-1km bulk shear should be plenty for organized storms and
possibly supercells. Deep layer shear increases through the day
while low level wind fields veer with approaching dry slot and
Pacific front. Model soundings and SREF probabilities show sig
tor parameters around 3-5 Sunday morning. Tornado threat looks
highest in the morning with hail/wind threat through the
afternoon.

Overall it is hard to find factors that will limit the severe
threat as capping is not that great and strongest to the SW of the
area. The other concern will be if the upper level lift, jet
dynamics and PVA are enough out of phase with moisture/instability
axis that there is not enough lift to initiate convection or erode
what capping there is if any.

Monday Through Friday...
A Pacific front will have pushed through the area Monday morning
with a drier airmass in wake of the front. Southerly winds return
Tuesday bringing back some Gulf moisture, enough to support some
slight rain chances as a cold front pushes through the area
Tuesday night into Wednesday morning. GFS is slower with the front
and holds on to some overrunning precipitation while
ECMWF/Canadian both push the front through quickly. Those models
seem to have a better handle on the short wave trough moving
through the plains mid week than the GFS. An amplified upper level
pattern results for the end of the week and possible to get a re-
enforcing cold front for Friday which may actually keep
temperatures below normal by 2-5 degrees for the first week of
April.


.MARINE...

Moderate winds and seas should develop today and increase
overnight. Conditions should reach caution levels so went ahead
and issued SCEC for all Upper Texas Coastal waters for tonight.
Strong winds may develop Saturday and Saturday night so will need
to monitor for possible advisory conditions. A strong upper level
low will affect Texas over the weekend with showers and
thunderstorms, most of which will be inland. A front associated
with this system will push off the coast Monday morning allowing
for offshore winds. Onshore winds develop again on Tuesday.

Tide levels will need to be monitored Sunday morning into Sunday
afternoon with tides possibly 1-1.5 feet above normal. This will
put tides near 3.5 feet above MLLW late Sunday morning and could
impact Gulf facing beaches. Rip currents will also be a concern.

Overpeck


&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL) 86 63 83 68 78 / 0 0 20 60 80
Houston (IAH) 87 65 84 71 81 / 0 0 10 60 80
Galveston (GLS) 81 71 79 73 77 / 0 10 10 50 80

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION from this evening through
Saturday morning 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.


&&

$$

SHORT TERM...Luchs
LONG TERM...Overpeck
AVIATION...Luchs
MARINE...Overpeck