Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Houston/Galveston Texas
631 am CDT Sat Aug 23 2014
see the 12z aviation discussion below.
patchy ground fog and possibly some stratus may impact some of the
more rural sites between 12z and 15z. Otherwise...VFR is expected
through this evening with a possible return of patchy ground fog
at the more rural sites after 09z tonight. There is an outside
chance for isolated showers to form along a seabreeze mainly
during the afternoon period today. The latest high resolution
models are suggesting a time frame of about 17z to near 00z mainly
from the coast into the metropolitan Houston sites.
Previous discussion... /issued 402 am CDT Sat Aug 23 2014/
at 08z...weak high pressure was located over the west central Gulf
and a weak trough of low pressure remained over the western High
Plains. At 850 mb...high pressure was noted over eastern Louisiana
and low pressure was located over the intermountain west with a
trough extending south along the Arizona/nm state line. 850 mb moisture
was confined to coastal Louisiana and 850 temperatures had cooled 2 c at
lch. At 700 mb...high pressure was located over Louisiana with
very dry conditions noted at this level. At 250 mb...a strong
upper level ridge extended from eastern Missouri to eastern
Georgia. A weak upper level low was noted over north central
Mexico and another weak low was located over the Texas Panhandle.
Upper flow over East Texas looks confluent at 00z.
Models have been forecasting cooler 850 temperatures for today and the
00z cooling at lch may portend this development. Ensemble guidance
still supports very warm temperatures today as does the European model (ecmwf)
guidance. Will continue to forecast maximum temperatures in the upper 90s
inland...lower 90s coast. Middle levels remain dry and some of this
dry air will again mix to the surface so heat index values will
again remain close to the actual air temperature over the western
zones. The heat advisory for the coastal counties is a bit tenuous
as dew points are a bit lower than previous days. Not sure the 105 degree
threshold will be reached today but will maintain the heat
advisory. Prefer not to extend at the advisory into Sunday at this
time and wait and see how much dry air mixes to the surface this afternoon.
Can't rule out an isolated rain showers this afternoon but probabilities
are very small.
High pressure will remain in control through Monday with very warm
temperatures and dry conditions. Conditions will change quickly
Monday night as an inverted upper trough over the Gulf pushes west
toward the Upper Texas coast. This feature will bring a surge of
fairly deep tropical moisture into southeast Texas late Monday night with the
moisture hanging around through Friday. The NAM is particularly
aggressive with precipitable water values approaching 2.40 inches by 12z Tuesday.
An upper level trough moving slowly across the Central Plains
during the middle-week period will keep unsettled weather in the forecast
with mainly diurnal rain showers/thunderstorms and rain expected Tuesday through Friday. Will
carry chance probability of precipitation through Friday with convective temperatures around 90
and precipitable water values at or above 2.00 inches. Global models diverge significantly
Friday and beyond. The GFS brings a front through the area with
surface dew points falling into the 50s and precipitable water values dropping to less
than an inch. The GFS is considerably faster with the upper trough
moving across the Central Plains. The European model (ecmwf) is much slower with
the trough and never brings the front through the County Warning Area. The
Canadian is also slower with the trough so have leaned toward the
slower solutions. The European model (ecmwf) keeps the upper trough/weakness across
the Southern Plains through Sunday so will keep rain chances in the
forecast through next weekend. 43
high pressure over the Louisiana coast will drift westward over the
Texas coast today and Sunday. The models differ by the middle of the
upcoming week. Preferred the European model (ecmwf) over the GFS and kept onshore
winds in place.
Preliminary point temps/pops...
College Station (cll) 98 75 99 76 100 / 10 10 10 10 10
Houston (iah) 97 77 97 77 99 / 10 10 10 10 10
Galveston (gls) 92 83 91 83 92 / 10 10 10 10 10
Texas...heat advisory until 7 PM CDT this evening for the following