Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Houston/Galveston Texas
616 am CDT Fri Jul 19 2019
Aviation [12z taf issuance]...
Low stratus and isolated patches of fog are cropping up across the
area this morning. Heaviest cloud cover is in the north, and
explicitly include an MVFR ceiling at cll. MVFR also possible at
the I-45 terminals (fog at cxo, ceilings at others) but not enough
confidence to explicitly put in the tafs. If it occurs, look for
it to be brief right around daybreak. After that, look for sky
cover to decrease into the afternoon, with bases rising above VFR
(though ceilings are unlikely anyway) and south winds picking up
to around 10 knots. Finally, look for something approximating
Previous discussion /issued 337 am CDT Fri Jul 19 2019/...
- increasing thunderstorm chances through the weekend into early
- Change in upper level pattern will allow for a front to move
through the area Tuesday into Wednesday.
Short term [today and tonight]...
Satellite and observations show mostly clear skies across
southeast Texas underneath ridging, though there are a few flecks
of clouds at the 2000ish foot level. This will have little impact
on sensible weather at the surface, but may need to be accounted
for in aviation forecasts, along with some patchy fog in the usual
foggy spots. Radar indicates perhaps a nocturnal shower or two
over the Gulf, though most of the returns on radar look to be sea
Have spread a slight chance of sprinkles near the coast this
morning, just in case any marine showers drift onshore, but
largely think we'll be looking at generally scattered clouds (or
less) thanks to the ridging in place, and precipitable water in
the 1.3 to 1.5 inch range. This should largely suppress rain
chances, but it's hard to completely rule out a slight chance of
sprinkles or even an isolated shower/storm with a seabreeze
boundary and strong diurnal heating.
On the flip side, high dewpoints will keep low temperatures this
morning high for yet another day. This will provide a solid floor
from which to see strong heating into the afternoon. Inland, we
should see another day with highs in the low to middle 90s, closer
to 90 degrees at the coast. Of course, there is little surprise
that we will likely see heat indices rising above the century
mark today into the 100-105 range for most of the area.
Long term [saturday through friday]...
Thunderstorm chances increase over the weekend due to a couple of
factors. First higher moisture gets drawn up from the Gulf
Saturday into Sunday such that more scattered showers and
thunderstorms will be possible by Sunday. This also lines up with
when an inverted trough sneaks under the upper level ridge and
moves across the northern Gulf Coast reaching the area late
Sunday. This also allows for lower 500mb heights over the area
along with slightly increased large scale ascent. While this is
happening, 500mb heights increase over the 4 corners region into
the Great Basin. Sunday into Monday the pattern becomes more
amplified as the ridge increases.
By Monday night into Tuesday the upper level pattern becomes
amplified with the ridge over the Great Basin and a substantial
trough over the Great Lakes. This pattern should persist through
much of the week with naefs/European model (ecmwf) ensembles showing 500mb heights
in the 90th percentile associated with this ridge. Tuesday through
Thursday the trough axis extends from the Great Lakes all the way
into Texas creating a weakness in the ridging between the ridge
to the west and ridging over the western Atlantic. This also
allows for a front to move into the area Monday night and Tuesday.
This is also where we will go with higher pops for scattered
showers and storms along the frontal boundary. The forecast will
maintain thunderstorm chances through the rest of the week with
the front stalling off the coast and then dissipating. Higher
moisture pooled along the front in the Gulf then moves back north
later in the week thereby needing thunderstorm chances to
Overall the main impacts from storms next week will be typical
heavy rainfall, gusty winds and lightning. Storms should stay
below severe levels but would not be surprised at an isolated
strong/severe storm Sunday into Monday before the front arrives.
The main threat for a severe storm will be downburst winds as
freezing levels will be quite high limiting hail growth.
Typical summertime conditions on the bays and Gulf are expected at
least through the weekend. This is complete with daytime winds
closer to 10 knots during the day, drifting upwards to around 15
knots. This is right around the scec threshold, but with waves
expected to be around 3 feet or less, have opted against the
caution flag at this time.
At the beaches, Galveston beach patrol reports mainly moderate rip
currents, but an occasionally strong rip current is being
observed. As with the scec, will abstain from a rip current
statement at this time, but if beach patrol indicates conditions
are worsening, a statement may be issued.
Looking ahead, a weak cold front could enter the coastal waters
as we push towards the middle of next week.
Preliminary point temps/pops...
College Station (cll) 96 77 96 77 96 / 10 0 10 0 10
Houston (iah) 94 79 93 78 93 / 20 10 20 10 30
Galveston (gls) 90 82 90 82 90 / 20 20 20 10 20