Mesoscale Discussion 0123
NWS Storm Prediction Center Norman OK
0657 AM CST Sat Feb 23 2019
Areas affected...eastern Texas...western and northern
Louisiana...southern Arkansas
Concerning...Severe potential...Watch possible
Valid 231257Z - 231500Z
Probability of Watch Issuance...60 percent
SUMMARY...Storms are expected to gradually develop over east TX into
LA and southern AR this morning. A few storms could become severe,
and trends will be monitored for a possible watch.
DISCUSSION...As of 13Z, a warm front extends from OCH TX across
northern LA and into north-central MS, with a moist air mass to the
south (upper 60s to near 70 F dewpoints). Morning soundings from the
region indicate steep midlevel lapse rates in place, with a capping
inversion just below 700 mb. As such, minor convective inhibition
exists even for areas in the warm sector, such as LCH where around
50 J/kg MLCIN was noted on the 12Z sounding.
Radar trends show increasing elevated thunderstorms over northeast
TX, north of the warm front and closer to the upper vort max track
where cooling aloft will take place. However, a cold front is
approaching the area from the west, and will eventually enhance lift
both along the intersecting warm front and southward across the warm
sector. During this time, the low-level jet will also strengthen to
around 50 kt.
Increasing lift of a moist air mass is expected to erode CIN through
late morning, with an eventual line of thunderstorms along the wind
shift, some possibly supercells. Ample low-level effective SRH would
support a tornado threat along and south of the warm front, while
hail is possible to the north. Thus, while the primary severe risk
today will be along and east of the MS river, a watch is possible
earlier today for western areas.
Cromagnum wrote: ↑Sat Feb 23, 2019 12:03 am
It's disgusting outside.
Disgustingly muggy outside this morning! Last night the mist was terrible as we were leaving the BBQ cookoff event. Just misting enough to make things muddy and make it so I couldn't see through my glasses. LOL
Cromagnum wrote: ↑Sun Feb 24, 2019 4:58 pm
Cool is good. Dry would be better.
Honestly, I don’t really see any rain on the horizon. Maybe more mist/drizzle and fog though.
Yard doesn't dry up when it doesn't that around the clock though
Not sure where you are, but our yard here in Wharton has dried up pretty well over the past couple weeks. Not much standing water around anymore. Farmers are even able to get in the fields now to start planting.
The ground is still saturated as you travel N and E of Metro Houston. Liberty County particularly near Moss Hill is a swamp. Even my backyard is wet. What concerns me is we head into a wet pattern as the cold weather retreats and a Western trough becomes established leaving our Region in a weakness between a SE Ridge/Western trough upper air pattern. Weak El Nino and Spring Storm Season may develop as we head into March.
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srainhoutx wrote: ↑Sun Feb 24, 2019 8:00 pm
The ground is still saturated as you travel N and E of Metro Houston. Liberty County particularly near Moss Hill is a swamp. Even my backyard is wet. What concerns me is we head into a wet pattern as the cold weather retreats and a Western trough becomes established leaving our Region in a weakness between a SE Ridge/Western trough upper air pattern. Weak El Nino and Spring Storm Season may develop as we head into March.
If there’s a SE ridge then why’s it been raining there so much?
Rain chances increase after midnight as a developing Coastal trough and warm front head toward the Coast. Strong storms are possible with hail being the primary concern.
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Active weather pattern will continue this week with several chances of rainfall and potential for a fairly significant cold front next weekend.
Southwesterly flow aloft doing its thing this morning with clouds and moisture starting to increase over the surface cold dome…sound familiar? Radar shows some showers over the Gulf waters likely being forced by a passing weak disturbance which none of the forecast models showed. A few of the models are trying to generate a few light showers this afternoon along the coast as moisture increases.
Better rain chances come tonight into Tuesday as a warm front moves toward the area from the south and lift increases ahead of a short wave in the sub-tropical SW flow aloft. Cloud decks will lower and thicken this evening and expected drizzle and light rain to begin to develop by mid evening and expand in coverage and intensity into Tuesday. Instability increases some on Tuesday above the surface and a few elevated thunderstorms may develop. SPC has outlooked a good part of the area for a “marginal” risk of severe weather and think a few of the stronger thunderstorms could produce some large hail. Rainfall amounts of .25-.75 of an inch look likely late today-early Wednesday.
Surface warm front lifts northward on Tuesday night with the area becoming warm sectored. This will result in showers and thunderstorms gradually ending and shifting NE of the area although I would not rule out a few showers moving S to N in the warm air advection regime on Wednesday. Other item of concern will be our coastal TX “friend” the sea fog as warm 60 degree dewpoints move over near 60 degree water temperatures. Dense sea fog bank will likely develop late Tuesday and linger into Thursday across the coastal locations.
Some of the models are attempting to move a cold front into the area on Thursday as a very cold air mass moves into the plains. The NAM model which did exceedingly well the weekend of the 16th with a shallow dense cold air mass is showing this front pushing into and across the area on Thursday while the other global models keep the front stalled to our north. This will have big ramifications on the temperature forecast for Thursday and Friday as we could approach 80 if the front does not come through or have highs in the 50’s and 60’s if it does move through. I am leaning toward the NAM solution since it tends to handle these dense, shallow, cold air masses better than the global models, but would like to see a few more runs before having much confidence.
Regardless of what happens Thursday and Friday, a significant cold front will move across the region on Saturday. A strong arctic air mass will plunge down the plains and across TX on Saturday allowing very cold conditions for early March. Front should clear the coast on Saturday with temperatures falling into the 50’s and maybe even the 40’s during the day under strong cold air advection. Strong lift begins to develop behind the front as the SW flow aloft overruns the boundary and expect widespread rains to develop Sunday-Tuesday. Will have to keep a close eye on surface temperatures during this period as some areas could get close to freezing for morning lows.
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Area Forecast Discussion
National Weather Service Houston/Galveston TX
532 AM CST Mon Feb 25 2019
.AVIATION...
VFR conditions will deteriorate as cloud cover returns to SE TX
and MVFR ceilings fill in along the coast by late afternoon and
spread inland this evening. Winds will be out of the east today
between 5-15 kts, becoming southeasterly by tomorrow morning.
Short term guidance has struggled to initialize well this
morning considering there are currently showers over the Gulf
waters and no solutions showing any sign of precipitation. That
being said, solutions also hint at the possibility of light
showers streaming west to east across the coastal TAF sites later
this afternoon, but not confident enough at this time to include
in TAF at LBX or GLS. The chance for showers increases as we
move into the evening hours starting around 03Z at the coastal
sites and closer to 09Z at IAH. Forecast soundings show a deep
saturated layer from the surface up through 700mb, so showers and
isolated thunderstorms will be possible. Have left out VCTS
wording at this time due to low confidence in placement of the
potential isolated thunder.
Ceilings will continue to lower by the end of the TAF period with
MVFR/IFR ceilings possible area wide. Additionally, sea fog could
impact visibilities at LBX and GLS early tomorrow morning.
Hathaway
&&
.PREV DISCUSSION... /ISSUED 410 AM CST Mon Feb 25 2019/
DISCUSSION...
At 3 AM, high pressure was located over the mid Mississippi
Valley with a weak trough of low pressure over eastern New
Mexico. Satellite imagery is showing mid to high level cloud cover
moving overhead. Today should start out dry but as the surface
high moves east, winds will become E-SE and low level moisture
will begin to return. A weak disturbance moving up the coast this
afternoon could produce some light rain but not sure low levels
will saturate enough to allow precip to reach the ground. Will
carry small PoPs near the coast for this afternoon but most of the
area will remain dry.
Moisture advection will continue tonight and forecast soundings
show a deepening saturated layer from the surface to around 700
mb. Soundings also show a weak cap near 700 mb but the low levels
look moist enough to generate showers as a coastal trough tries
to develop. Showers should become more widespread after midnight
as the coastal trough strengthens and moisture levels increase. A
warm front will approach the coast on Tuesday and PW values
increase to 1.60 inches. Low level warm advection is forecast to
increase north of the boundary and this will likely be the primary
forcing mechanism for elevated convection over much of SE TX. SPC
has placed much of SE TX in a Marginal Risk on Tuesday for
primarily the potential for large hail. The disturbance will exit
the region on Wednesday and there should be a lull in
precipitation as dry air develops in the 850-500 mb layer and
strong capping develops near 850 mb. Warm and moist air flowing
over cooler shelf waters will probably allow sea fog to develop
beginning as early as Tuesday and this could linger through the
end of the week. Coastal communities will probably endure
visibility below a 1/2 mile at times.
A lot of uncertainty on Thursday as the NAM/ECMWF bring a cold
front into the area. The GFS stalls the front north of the area.
The Canadian supports the NAM and a few weekends ago the NAM
handled the shallow cool airmass better than the GFS. Have leaned
toward a blend of the GFS and WPC but think the NAM may be on to
something and temperatures on Thursday could be significantly
colder than currently forecast. There has been a lot of model run
to run inconsistency and confidence is low.
What happens on Thursday will have some impact on Friday`s
temperatures and the timing of Saturday`s front. If the front
comes through on Thursday, cooler temps will prevail on Friday and
the Saturday front won`t come through until Saturday evening. If
the GFS is correct the Saturday front will arrive early Saturday
morning. Have tried to split the timing differences and blended
temperatures for Friday and Saturday. Post frontal rains should
develop Sunday into Monday as strong isentropic upglide develops
in the wake of the weekend front. 43
MARINE...
High pressure over Texas will slide eastward today. Observations
over the past few hours have ranged between 15 to 20 kts sustained
with gust near 25 kts in both the near and offshore waters, and seas
around 5 feet. A Small Craft Advisory will remain in effect through
noon today, but small craft should exercise caution through the
remainder of the afternoon and into the evening hours.
The pressure gradient will slacken furthermore early Tuesday, and
light to moderate southeasterly winds will prevail. Tides will be
worth watching as a prolonged east to southeast fetch may result in
coastal run up along Gulf facing beaches as early as this afternoon.
Tide levels are forecast to be about 2.5 feet above MLLW.
Additionally, the chance for the development of sea fog will return
early Tuesday morning across the western waters and Matagorda Bay
before spreading eastward by late morning. As warm air is advected
over the colder shelf waters, favorable conditions for sea fog will
continue through the week, hindering visibilities until the passage
of our next strong cold front on Saturday. Seas will range between 2
to 3 feet through most of the week. Showers and isolated
thunderstorms will be possible over the bays and Gulf waters this
afternoon and through Wednesday.
The next cold front is expected to push through the Gulf waters
sometime on Saturday. There is still ample disagreement in the
timing of this boundary amongst global guidance. Most recent
solutions have the GFS the fastest with the passage, with the front
reaching the Gulf by late morning Saturday, while the Canadian and
ECMWF solutions fall behind by about six to twelve hours.
Regardless, SCA criteria will likely be reached behind this feature
and seas will once again build to 5 to 8 feet in the Gulf waters.
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...Small Craft Advisory until noon CST today for the following
zones: Coastal waters from Freeport to Matagorda Ship
Channel TX out 20 NM...Coastal waters from High Island to
Freeport TX out 20 NM...Waters from Freeport to Matagorda
Ship Channel TX from 20 to 60 NM...Waters from High Island
to Freeport TX from 20 to 60 NM.
SMALL CRAFT SHOULD EXERCISE CAUTION from noon CST today through
this evening for the following zones: Coastal waters from
Freeport to Matagorda Ship Channel TX out 20 NM...Coastal
waters from High Island to Freeport TX out 20 NM...Waters
from Freeport to Matagorda Ship Channel TX from 20 to 60
NM...Waters from High Island to Freeport TX from 20 to 60
NM.
