Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Houston/Galveston Texas
301 PM CST Thursday Dec 25 2014
clouds will continue to increase overnight as low level moisture
is drawn back into southeast Texas. Southerly winds...winds and
cloud cover will produce temperatures about 15 to 20 degrees
warmer than last night. Precipitable water values increase to around 1.1 inches of
Friday and forecast soundings show a saturated layer up to around 800
mb. Probably get some streamer showers beneath the cap. A weak
upper level disturbance will keep rain in the forecast on Friday
night. A cold front will approach southeast Texas on Saturday. Still some
timing differences with the front but at this time...it appears
the front will move through kcll around 15z...kiah around 20z and
kgls around 00z. Dynamics on Saturday looking a bit better with
cape values near 1500...lifted indice's -3 to -5...tt's in the lower 50s and
k index in the upper 30s. Helicity values are around 200 as well.
Southeast Texas will also get lift enhanced from a departing 140 knots rrq.
Raised probability of precipitation a bit on Saturday and would not be surprised if some
of the storms on Saturday become strong to severe. The GFS and
European model (ecmwf) continue to push the weak upper level trough over SW Texas to
the east faster than the NAM and Canadian. Post frontal rains will
continue Saturday night into early Sunday as southwest winds aloft
over ride cooler north-NE surface winds. The NAM/Canadian diverge from the
GFS/European model (ecmwf) on Sunday with the NAM/can holding the upper trough to
the west and maintaining the SW flow aloft. The GFS/ec move the
trough eastward and the upper flow becomes zonal ending the
isentropic lift. Have leaned toward the GFS/European model (ecmwf) solution and
feel rain will diminish by Sunday afternoon.
There should be some brief clearing Monday/Monday night before clouds
return on Tuesday as the next upper trough drops south into Arizona.
The flow aloft will once again become southwest and a coastal low
will develop east of kbro. The combination of these features
coupled with additional lift from the slow moving upper level
trough should yield patchy light rain each day through Friday.
Temperatures will be on the cold side as a 1040 mb high slides
south into the Southern Plains on Wednesday and another 1040 high
approaches the area next Friday. Despite the cold temperatures...
at least for now...it appears all the precipitation will remain
A developing surface low in the Lee of the Rocky Mountains will
encourage elevated onshore flow to continue into Friday
morning...and mariners in small craft should exercise caution over
the coastal waters tonight. Temperatures over the shallower shelf
waters are currently around 61 to 63 degrees. With onshore flow
continuing to advect warm...moist air over these cooler waters...the
possibility exists for sea fog development late Friday night into
Saturday morning. The limiting factor for this will be the warmer
waters that are also pushed closer to shore by these southerly to
southeasterly winds...so confidence is not high in sea fog formation
at the moment but will continue to monitor trends.
As the aforementioned surface low ejects across the Central Plains
Saturday...an attendant cold front will push into southeast Texas
Saturday afternoon and reach the coast Saturday night. Isolated
thunderstorms associated with this cold front will be possible over
the bays and coastal waters Saturday and Sunday. Elevated offshore
winds behind the front may warrant caution flags Sunday. A return to
onshore flow at the beginning of next week will be short-
lived...with the next frontal system moving across the coastal
waters by mid-week.
Preliminary point temps/pops...
College Station (cll) 49 69 58 62 42 / 10 30 40 50 40
Houston (iah) 54 72 62 71 47 / 10 30 50 70 60
Galveston (gls) 62 69 63 69 53 / 10 20 40 60 60
GM...small craft should exercise caution from 6 PM CST this evening
through late tonight 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.