Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Houston/Galveston Texas
1053 am CDT Wednesday Apr 1 2015
morning forecast update.
short wave trough on water vapor imagery over S Texas should continue
to push east into the Gulf/southeast Texas later this afternoon. Latest surface
analysis/composite map has warm sector airmass over the region
with surface dewpoints in middle 60s to low 70s. Area radar show
convection over S Texas that should push east through the rest of the
day with the shortwave trough. Both crp/lch 12z soundings show dry
air in 850-700mb layer that will need to be overcome to support
more wide spread convection. Latest rap/hrrr show that this may
happen but dry air will impact rainfall totals today as the system
passes. Think convection could develop mainly between 20z and 00z
Thursday this evening for the Houston area. Only real changes to the
foreacst were to increase rain chances along the coast based on
short range models. Rest of the forecast looks on track.
Previous discussion... /issued 635 am CDT Wednesday Apr 1 2015/
there is a mix of MVFR/IFR ceilings and visibilities across southeast Texas early
this morning. 12z tafs have area becoming VFR later this morning and
on through this afternoon...but it is not out of the question that MVFR
ceilings could persist longer than anticipated. Area radars are showing
rain showers/thunderstorms and rain already developing across deep south and south central Texas...
and this activity is moving to the northeast toward our area. Went ahead
and added thunderstorms in the vicinity to the tafs for this afternoon to account for this convection.
Reduced ceilings/visibilities will be possible in association with the
shra/tsra. Tafs have ceilings/visibilities coming back down to MVFR/IFR
levels tonight through early tomorrow morning. 42
Previous discussion... /issued 558 am CDT Wednesday Apr 1 2015/
updated to start chances for rain earlier. Isolated showers may
begin to affect the western counties before middle morning.
Previous discussion... /issued 422 am CDT Wednesday Apr 1 2015/
still looking at three main events over the next week...an upper
level shortwave today...a cold frontal passage on Friday...and
then a series of upper level systems over the weekend and early
The first upper level shortwave trough was moving into western
part of Texas early this morning. The system will be running up
against a low-level high pressure ridge that extended from the
northern Gulf of Mexico into southeastern Texas. The models
differed a bit on rainfall coverage with the event today. Liked a
combination of the high resolution models with the GFS and nam12.
The nambufr and gfsbufr forecast soundings actually show a decent
dry layer that does not erode until late afternoon. The rap13 and
nam12 bring coverage into the southwestern counties by early
afternoon. Decided to take a compromise and lower the probability of precipitation for
this morning and then bring the best chances for showers and
thunderstorms this afternoon. The upper level system will be out
of the area by middle evening.
A couple of warm days...especially Friday...will then occur as a
southwesterly flow develops. The models are then in agreement with
at least chance probability of precipitation ahead of the cold front that will move
through Friday afternoon and evening. All of the models actually
diminish the rain chances Friday night and Saturday. The GFS and
European model (ecmwf) differ on the strength of the upper level shortwave troughs
on Sunday the with GFS the more aggressive model of the two. Took
a consensus of both models for the rain forecast both days.
Tuesday is looking to be warmer as a middle and upper level high
pressure ridge developing over the Gulf extends northward into
March ended being one of the top 15 wettest months on record.
Here is a listing for the first-order climate sites...
Hobby Airport.......6.25 ranked 7th highest
city of Houston.....6.34 ranked 13th highest
city of Galveston...7.69 ranked 8th highest
College Station.....5.83 ranked 11th highest
The rainfall helped alleviate the drought conditions that were
experienced over Jackson...Wharton...and Matagorda counties.
Portions of these areas were under a moderate drought earlier this
year. The rainfall during the month of March brought improvement
to where only Jackson County was under abnormally dry conditions
at the end of the month. This was due mainly to long term
hydrological drought conditions on the local river system.
moderate south winds will persist through the end of the week.
Speeds could get close to caution levels through Thursday night...
but a majority of the area should peak in a 10 to 15 knot range.
The next cold front is still on schedule to race off the coast and
through the coastal waters late Friday night through early Saturday
morning with moderate to strong northeast winds and building seas
in its wake. Caution flags and advisories will likely be needed
behind the front...and parts of the coastal waters could see
sustained winds around 25 knots and seas up to 8 feet early on
Saturday. Winds behind the front will weaken Saturday night and
on into Sunday and become more east and southeast...and this
moderate onshore flow will be in the forecast for the start of
next week. 42
Preliminary point temps/pops...
College Station (cll) 80 66 84 68 79 / 50 20 20 10 40
Houston (iah) 81 68 84 70 82 / 40 20 20 10 40
Galveston (gls) 76 69 78 70 79 / 20 20 10 10 20