Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Lake Charles la
934 PM CDT Friday Apr 17 2015
severe mesoscale convective system trucking east-northeast at 30-35 kts across southeast Texas/coastal waters.
Kxih AWOS about 15 miles southeast of Galveston reported a 61 knot wind
gust as the apex of the Bow passed over this platform. Thus...for
this and the likehood of it continuing severe for the next 4-5
hours...Storm Prediction Center issued severe watch #71 through 2 am for southeast Texas counties/la
parishes along and S of I-10 including the coastal waters.
Afterwards...areas of rain showers/thunderstorms and rain likely to continue well into
Sat...adding to the flash flood threat of this weather system. Flash
Flood Watch continues through 6 PM Sat. Main adjustments were to
timing of probability of precipitation/weather and severe wording to forecast for the overnight
Previous discussion... /issued 721 PM CDT Friday Apr 17 2015/
for the 00z taf package.
difficult forecast this evening with uncertainty regarding evolution
of convective complex over southeast Texas the primary concern. Radar
imagery indicates a faster eastward progression than previous
model forecasts...thus have sped up the arrival at the kbpt...klch and
kaex terminals. Forecasts at kara and klft were left unchanged for
Previous discussion... /issued 344 PM CDT Friday Apr 17 2015/
our next heavy rain event appears to be taking shape well to our
west as regional 88ds show convection associated with next impulse
aloft and approaching middle-level speed maximum already developing over
western/cntl Texas at this time. This activity will continue pushing eastward through
the evening...while also further developing as increasing
environmental moistening takes place ahead of it...thus expecting
widespread showers and storms to develop or move into the area
tonight. Forecast soundings indicate good low-level shear/lapse
rates across the forecast area tonight...with best values across
the southwestern zones where severe wording was included in the
grids/zones. In addition as stated earlier...heavy rains are
expected to accompany this convection and thus the Flash Flood
Watch was extended to account.
Showers/storms will continue across the area tomorrow as yet
another impulse aloft slips into the region. The entire forecast
area is included in an Storm Prediction Center slight risk for tomorrow...however am a
little concerned about available instability given expected
earlier convection and how it may work over the atmosphere plus
limited heating from cloud cover/precip. For now am not inserting
severe mention into the Saturday grids/zones but am sure this will
be re-evaluated by later shifts...stay tuned.
Precipitation will begin working its way out of the forecast area
Saturday night and Sunday as the longwave trough axis shifts eastward
across the Southern Plains..and associated surface frontal boundary finally
crosses the area. At this time Monday looks dry as a nearly flow is prognosticated
through the column. However our pop-free forecast looks short-
lived for at least the western portions of the area as return flow
sets up in time for another weak disturbance moving out of Mexico.
The remainder of the forecast looks like a gradual repeat of the
past week as gradual moistening and periodic impulses aloft
combine for periods of convection beginning mid-week. However am
capping probability of precipitation in the low end chance range for now due to long-range
no flags anticipated through the period.
Preliminary point temps/pops...
aex 67 76 64 82 / 90 90 50 20
lch 69 77 65 82 / 90 90 50 20
lft 70 78 66 84 / 90 90 60 30
bpt 69 79 65 82 / 90 90 40 20
la...Flash Flood Watch through Saturday evening for laz027>033-
Texas...Flash Flood Watch through Saturday evening for txz180-201-215-