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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Monday
• 
• High: 58 °
• Low: 45 °
• T-Storms

• Tuesday
• 
• High: 74 °
• Low: 58 °
• Clear

• Wednesday
• 
• High: 74 °
• Low: 54 °
• T-Storms

• Thursday
• 
• High: 70 °
• Low: 45 °
• Partly Cloudy

• Friday
• 
• High: 65 °
• Low: 45 °
• Partly Cloudy

Area forecast discussion 
National Weather Service Houston/Galveston Texas 
830 PM CST sun Feb 12 2012 


Update... 
see evening update below. 


&& 


Discussion... 
very light rain or sleet is being reported across the region. Most 
of the precipitation is evaporating before reaching the ground but 
therein lies the problem. The sub cloud layer is so dry that 
evaporative cooling is freezing the remaining drops into sleet. 
Wet bulb zero is also around 1700 feet which is contributing to 
the sleet. The atmosphere is expected to warm overnight so feel the 
sleet threat overnight is minimal. Even the light rain threat 
should briefly diminish overnight before increasing again on 
Monday morning. Min temperatures will remain steady through 09z and then 
begin to warm before sunrise. 


As for Monday...a middle level trough will cross the Southern Plains 
while an area of low pressure develops along the middle coast. 
This low will move up the coast and a warm front will intrude on 
southeast Texas. Strong low level convergence and relatively high moisture 
levels should spell another round of rain on Monday. The greatest 
rainfall potential should be along and south of U.S.Hwy 59. 
Low jet increases to 55 knots between 15-18z and helicity values 
exceed 500 so feel the severe threat for coastal counties is 
warranted. Cape is still meager but with the warm front moving 
into southeast Texas during the morning...cape might just be a touch 
underdone. A few minor tweaks here and there but the integrity of 
the previous forecast is on the mark. 43 


&& 


Previous discussion... /issued 602 PM CST sun Feb 12 2012/ 


Aviation... 
unable upper level disturbance moving from west to east across the 
region is spreading an area of light rain mixed with light sleet 
across the area. Expect this trend to continue and ceilings will 
probably lower to around 050 by 03z. A second upper level 
disturbance will move across the area on Monday spreading rain 
across all of the region. Ceilings will lower to MVFR by around 15z 
and near IFR conditions after 18z. Warm front is expect to drift 
back north from the Gulf of Mexico. This will allow for additional 
instability and the possibility of thunderstorms mainly near the coast 
from 15z to 00z. Some of these storms could be severe and contain 
strong winds and the possibility of a weak tornado. During the day 
Monday ceilings will at or below IFR and visiblities will be MVFR for 
most of the day after 15z. 


Previous discussion... /issued 345 PM CST sun Feb 12 2012/ 


Discussion... 
it looks like another active start to the work week as far as 
weather is concerned. Cloud cover continues to increase with NE 
surface winds so maximum temperatures have been hard pressed to reach the 50s 
except for areas with mostly clear skies. Temperatures should not drop 
much tonight with warm advection increasing. Temperatures may warm a 
little overnight along the coast as moisture begins to move into 
southeast Texas early Monday morning. 


The main concern tomorrow will be the severe potential and heavy 
rainfall. The severe potential largely depends on instability as 
models are all agreeing that less than 500 j/kg of cape will be 
possible. Precipitation water values should reach 1.3-1.4 inches along 
the coast as the warm front moves inland during the day. Models 
suggest a weak wave to form on the front with a weak surface low that 
moves east during the day. This set up really enhances low level 
shear and model hodographs show quite a bit of turning in the 
lowest 3 km. The NAM has 0-3km srh reaching 700-900 m2/s2 over 
the southern half of the area. There will also be quite a bit of 
low level lift and strong qg frontogenesis. Storms may still 
become strong/severe given such strong forcing in the low levels 
and could take advantage of low level shear to spin up brief weak 
tornadoes as well as produce damaging winds. Heavy rainfall may 
be possible along the coast as well with precipitation water near 1.4 
inches but expect rapid storm motions so think quantitative precipitation forecast will remain 
below flash flood thresholds. Still warrants being monitored 
given the forcing in low levels. 


The next system on Wednesday could also produce a period of 
significant rainfall and severe weather. Model soundings suggest 
convective available potential energy of around 1000 j/kg and strong deep layer shear for storm 
organization. Precipitation water may be even more than on Monday with 
the GFS/NAM suggesting areas of 1.5-1.6 inches which would be 
right in line with 2 Standard devs above normal or near the 99th 
percentile on climatology precipitation water curves. The shortwave will still 
pass north of the area but bring a Pacific front into the area 
late Wednesday which will provide the necessary lift for storms mainly 
for the northern half of southeast Texas. Forecast will keep 50/60 probability of precipitation as 
models have not changed much with the timing of this system. 


Expect another break in the active weather Thursday/Friday with the 
Pacific front off the coast. The GFS/European model (ecmwf) still suggest the 
possibility of a coastal low forming in the northwest Gulf Sat/sun. 
Forecast looks on track with 20/30 probability of precipitation for the time being but 
looks like the models are having a tough time with the timing of 
this third shortwave trough and how far south it digs into the S 
rockies. The European model (ecmwf) is faster and weaker than the GFS but both 
suggest the possibility of a wet weekend next week. 


39 


Marine... 
moderate to strong east to southeast winds along with elevated 
seas and Bay waters will persist through Monday (caution in the 
bays... advisory offshore) when a storm system moves across the 
area. A light to moderate mainly onshore flow is then expected 
late Monday night through Wednesday evening...followed by the 
passage of the next cold front late Wednesday night through early 
Thursday morning. Behind the front...moderate to strong north to 
northeast winds along with elevated seas and Bay waters will 
develop and persist through the end of the week. Weekend weather 
has the potential to be a mess if a western Gulf surface low 
forms and moves across the area. 42 


&& 


Preliminary point temps/pops... 
College Station (cll) 42 54 44 72 61 / 60 90 10 10 20 
Houston (iah) 43 63 50 74 62 / 40 90 20 10 20 
Galveston (gls) 47 65 56 69 63 / 40 90 30 10 20 


&& 


Hgx watches/warnings/advisories... 
Texas...none. 
GM...small craft should exercise caution through Monday afternoon for 
the following zones: Galveston Bay...Matagorda Bay. 


Small Craft Advisory until 6 PM CST Monday for the following 
zones: waters from Freeport to the Matagorda Ship Channel 
20 nm to 60 nm...waters from Freeport to the Matagorda Ship 
Channel out 20 nm...waters from High Island to Freeport 20 
to 60 nm...waters from High Island to Freeport out 20 nm. 


&& 


$$ 


Discussion...43