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Area forecast discussion 
National Weather Service Houston/Galveston Texas
720 am CDT Monday Jul 28 2014

Update...
update for dense fog.

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Discussion...
visibility will bounce around 1 mile to 1/4 mile in most areas SW
of Houston due to fog so issed dense fog advsiory for next couple
of hours. Updated forecast has been sent.

39

&&

Previous discussion... /issued 642 am CDT Monday Jul 28 2014/

Discussion...
see aviation for 12z taf issuance

Aviation...
corridor of IFR ceilings extending from near San Antonio to La Grange
is spreading eastward and may produce some low clouds at cll early
this morning. Elsewhere patchy fog are developing across our
southwestern counties with visibilities variable at sgr and lbx. All of
this should come to an end by middle morning with VFR conditions
expected through the remainder of the day. Winds will be variable
and light today as a frontal boundary across North Texas sags
southward. Some showers are possible this evening for cll/uts
depending upon how far south the boundary can make it. 38

Previous discussion... /issued 420 am CDT Monday Jul 28 2014/

Discussion...
surface analysis has cold frontal boundary stretching from the middle-
south across S plains into Texas Panhandle where mesoscale convective system has developed.
GOES sounder precipitation water shows a swath of deep moisture with precipitable water
values of 2 inches mainly across the arklatex and Red River
region or just south of the frontal boundary. This is also where
other scattered storms have developed across S OK. Upper air analysis at
500mb from 00z soundings show a broad upper level ridge from the
Great Basin to North Texas into the north Gulf. Heights are higher than
previously prognosticated and suggest a broader area of subsidence. That
said deep convection is developing under the ridge due to surface
convergence with the frontal boundary and a weak trough axis
moving through the Midwest back to the S plains. Think rain
chances today and tonight may be more limited than forecast. The
ridge is stronger so it will take strong low level convergence
with the frontal boundary for convection to develop. Then again
it is hard to tell how far south the frontal boundary will sag
into Texas as it will more than likely become stationary into Tuesday.
Models are not indicating much quantitative precipitation forecast from convection so could just
leave 20 probability of precipitation for tonight into Tuesday. Think it will be better to
just leave the 30 probability of precipitation in the forecast given the chance of the
front pushing as far south as the models suggest. This will mainly
just affect the northern most areas of the forecast area.

Tuesday/Wednesday think mainly 20/30 probability of precipitation will be on track again and could
be a bit high. The upper ridge really does not weaken until Wednesday
so could expect hot conditions to continue the next couple of
days. The frontal boundary slowly dissipates Tuesday/Wednesday but still
could be the focus for thunderstorm activity. Outflow from storm
complexes could easily maintain some frontal continuity for the
middle of the week.

Synoptic models seem to be trending towards a more wet end of the
week. Both the GFS/European model (ecmwf) bring a short wave trough across the
plains Thursday into Friday. This seems to force quite a bit of precipitation
over OK and North Texas. This initial convectively induced precipitation
develops well north of the area but looks like another mesoscale convective system could
develop over the east half of Texas Friday morning as the frontal boundary
finally pushes farther into the area. Will keep 30 probability of precipitation in the
forecast but lack forecast confidence to go higher with rain
chances since models have not been performing well with trends in
the ridge. Plus quite a bit of the forecast will hinge on
mesoscale details which cannot be determined at this time. That
said the GFS and European model (ecmwf) are more robust with rain chances headed
into the end of the week with the frontal boundary stalled across
the area. The 500 mb ridge has also sufficiently weakened to near
588 dm heights with northwest flow aloft. Overall think that since the
models have done a poor job with the evolution of the
ridge...there is little confidence in rain chances to the start of
the week but look for chances to increase for the end of the week.

39

Marine...
light to moderate south to southwest winds will persist through the
first half of the week. Winds will remain variable through the end
of the week as a frontal boundary approaches southeast Texas. This
front may push offshore late in the week or early next week bringing
light offshore winds. 38

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Preliminary point temps/pops...
College Station (cll) 97 76 96 76 96 / 20 30 30 20 20
Houston (iah) 97 76 95 76 95 / 10 30 30 20 20
Galveston (gls) 91 81 91 80 91 / 10 20 30 20 20

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Hgx watches/warnings/advisories...
Texas...dense fog advisory until 9 am CDT this morning for the following
zones: Brazoria...Fort Bend...Matagorda...Wharton.

GM...none.
&&

$$

Discussion...39

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