Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Houston/Galveston Texas
658 PM CDT Friday Mar 14 2014
updated aviation section.
with onshore flow expect low levels to continue to moisten with
ceilings dropping into the MVFR range most taf sites overnight and
continuing Saturday. Also may see some light showers break out
beneath the cap especially Saturday. Best chance of more moderate
showers and even a few thunderstorms looks to be late Saturday
afternoon and evening...with best chance of thunder over northern
areas...perhaps cll and uts...Saturday evening closer to the upper
level disturbance and associated forcing...cold pool aloft. 46
Previous discussion... /issued 321 PM CDT Friday Mar 14 2014/
.Corrected to add discussion on slight chance of rain Sunday
despite plenty of cloud cover today maximum temperatures look like they have
reached the low 70s maybe middle 70s in a few spots. Strong southerly
winds have allowed for some low level moisture to return with surface
dewpoint temperatures near 60 right along the coast. Colder Gulf waters
have limited the quality of Gulf moisture holding dewpoints into
the low 60s but not a lot higher.
Water vapor imagery shows upper low over the desert SW about to
move across the S rockies tonight into Saturday. Second strong
shortwave was moving into the Pacific northwest. These two systems should
come more in phase Saturday night as the second wave drops into
the S rockies. The 12z models are all in pretty good agreement
with that idea but details are still different. Think GFS/European model (ecmwf)
are closer together with second shortwave phasing in and closing
off over the Rio Grande for Sunday. NAM is a bit more progressive
First upper low will be the driver for severe weather potential
tomorrow and tomorrow night. Think best probabilities for severe
weather will be more over c Texas and North Texas late Saturday. Storms
still could develop over Brazos Valley during this time and push
east into the night. Upper low should open up a bit as it moves
east and also support a front pushing into the area overnight.
Front may also initiate convection over the area with some strong
storms possible. Severe threat may be limited by a couple of
factors. First think best large scale lift will remain north of
the area which would not be much of a factor in eroding the cap.
Second cap is becoming more pronounced as evidenced by morning
soundings and expect this trend to continue. Models erode this cap
fairly quickly even with best lift north of the area. Third
instability looks marginal with maybe 1000 j/kg. Deep layer shear
would be plenty for organized storm structures so could southeast Bow
echo structures if there is enough instability. Given that hail
and high winds would be the main impacts.
Strong cold front will push through Sunday with gusty north winds
behind it. Will probably need a Wind Advisory given the tight
pressure gradient. Decided to keep some small rain chances in the
forecast for Sunday despite the cold front and possibly enough
moisture being scoured out of the area. Main reason is for upper
low out west moving over the region. Expect very cold temperatures aloft
supporting a few elevated showers or storms. Activity will be
limited with lack of moisture.
Cold airmass should settle over the area for Monday and do not
expect much warming with 850mb temperatures hanging around 5c with cold
advection. Temperature roller coaster will continue as min temperatures
on Monday start in the 30s/40s with maximum temperatures on Tuesday back into
the middle/upper 70s. GFS/European model (ecmwf) having some differences with regards
to next weak front. GFS holds front north of the area while European model (ecmwf)
pushes it through. Think GFS may be on right track since the
system looks rather progressive so trended forecast that
direction. Overall expect temperatures to remain near normal for the end
of next week.
with the ridge retreating eastward...onshore winds will continue
to slowly strengthen tonight. Winds may reach caution levels later
tonight...but for the most part expect at most around 15 knots.
Dewpoints will also slowly climb into the lower 60s tonight. This
should be enough for at least some patchy sea fog development...
especially near the coast. The cold front will move off the coast
Sunday morning with the strongest winds affecting Matagorda Bay
and the areas west of Freeport by late Sunday morning. By sunset
Sunday all areas will experience advisory conditions. The latest
nam12 and mav guidance both indicate at least gusts to gale over
the offshore waters Sunday night...and one of the later shifts
tonight may issue a gale watch for Sunday night if needed. A
gradual decrease in the winds will occur Monday with the wind
speeds below advisory levels by Monday afternoon.
Preliminary point temps/pops...
College Station (cll) 72 62 72 58 63 / 10 30 50 50 20
Houston (iah) 72 62 74 62 68 / 10 30 40 50 20
Galveston (gls) 70 62 71 61 67 / 10 20 30 40 20