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Area forecast discussion 
National Weather Service Houston/Galveston Texas
941 PM CDT Monday Apr 20 2015

Update...
evening forecast update.

&&

Discussion...
still a fairly strong southern jet stream over the region which
has been producing some high level radar returns. Doubt any of the
precipitation is hitting the ground. High clouds will be
thickening over the region tonight based on water vapor/infrared
satellite imagery. Min temperatures may not get quite as cool as forecast
but think forecast is close enough. Overall no real changes in the
forecast as it looks on track.

39

&&

Previous discussion... /issued 615 PM CDT Monday Apr 20 2015/

Aviation...
VFR for the 21/00z tafs. Surface high pressure centered to the north and
NE of the area tonight will move off to the east tomorrow. This will
allow for the light winds tonight to increase tomorrow and be more
out of the east and southeast. Anticipate seeing lowering clouds as
the day progresses tomorrow...but think that any MVFR ceilings will
hold off until tomorrow night or early Wednesday morning. Look for
the area's next best shot of seeing some rain showers/thunderstorms and rain back in the tafs
some time on Wednesday. 42

Previous discussion... /issued 344 PM CDT Monday Apr 20 2015/

Discussion...
an area of high pressure at the surface has brought a pleasant day
across southeast Texas. Partly to mostly cloudy skies have been
compliments of the subtropical jet moving high level cloudiness
overhead. The west-southwesterly pattern aloft will persist
through the upcoming weekend.

The surface high will move east of the area and onshore winds
will return late tomorrow. A weak disturbance aloft will first
bring a slight chance for thunderstorms over the northern counties
during the afternoon and early evening. Both the Texas tech WRF
and the nam12 agree with this scenario. A model consensus also
brings chances of rain to the offshore waters as well. Expect
slightly better rain and thunderstorm chances on Wednesday with
better onshore flow. The GFS model precipitable water/S approach 1.9 inches over
the southern third of the forecast area on Wednesday as well.

A deepening upper level trough over the southern rockies into
western Mexico will then provide a downstream ridge over the state
late on Wednesday into Thursday. This should provide for a more
subsident flow aloft and less chances for daytime rain and
thunderstorms. As the ridge moves overhead and east on Thursday
night and Friday...a diffluent flow aloft will combine with a
shortwave trough on Friday. Model precipitable water/S also approach 2 inches on
Friday...and am expecting more widespread showers and
thunderstorms.

Another less potent upper level system moves overhead late Sunday
into Monday. However...both the GFS and European model (ecmwf) differ for Monday.
Am leaning toward the European model (ecmwf) given that the GFS is moving a cold
front off the coast early on Monday while the European model (ecmwf) moving a
weaker front through late on Monday and into the Monday night
period.

40

Climate...
just issued a public information statement for the rainfall
through April 19th. To summarize...all of the climate sites have
reported above normal rainfall to date...with all now reporting
above normal rainfall for the year-to-date. Here is a summary
table for the first- and second-order sites.

Rainfall for April year-to-date rainfall
site total departure total departure

City of Houston 6.40 +3.91 16.57 +4.09
Galveston 4.51 +2.44 18.34 +6.34
hobby Airport 8.07 +5.84 20.20 +7.69
College Station 2.36 +0.82 15.60 +4.80
Conroe 2.20 +0.82 12.17 +0.56
Huntsville 4.68 +2.76 17.73 +5.52
dw Hooks Airport 5.93 +3.83 16.19 +3.92
Sugar Land 8.67 +6.44 17.85 +5.55
Angleton 2.95 +1.34 15.94 +3.47
Palacios 3.02 +2.36 10.70 +1.32
Clover Field 4.39 +2.17 16.30 +3.65

40

Marine...
should be able to drop the caution flags offshore late this
afternoon or early evening as speeds continue to slightly
diminish. Winds will swing around to the east and remain around
15kt for most of the waters Tuesday. May be borderline caution
criteria at times before 2 PM. Otherwise...winds will continue to
veer back to the southeast by midweek and generally remain in the 10-15kt
range for the remainder of the work week with seas mainly 4ft or
less. 47

Previous discussion... /issued 1219 PM CDT Monday Apr 20 2015/

Aviation...
VFR for the next 24+ hours with just some high/middle level clouds
streaming overhead from the west. 47

Previous discussion... /issued 1023 am CDT Monday Apr 20 2015/
the surface cold front was well off the coast at middle morning...
with high pressure building in from the northwest. Even with the
cooler and drier airmass in place...a strong subtropical jet
stream aloft will provide plenty of high clouds throughout the
day. This will help keep the temperatures down across the area.

The current forecast looks to be on track and no changes are
planned at this time. 40

&&

Preliminary point temps/pops...
College Station (cll) 54 78 64 82 69 / 10 20 10 30 30
Houston (iah) 58 79 65 81 70 / 0 10 10 30 30
Galveston (gls) 67 77 71 80 72 / 10 10 10 20 20

&&

Hgx watches/warnings/advisories...
Texas...none.
GM...small craft should exercise caution until 10 PM CDT this evening
for the following zones: waters from Freeport to the
Matagorda Ship Channel 20 nm to 60 nm...waters from High
Island to Freeport 20 to 60 nm.

&&

$$

Discussion...39

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