September 2017 - Rain Chances/End Of Month Cold Front

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Re: September 2017 - Rain Chances/End Of Month Cold Front

Postby Katdaddy » Wed Sep 27, 2017 5:20 am

Another partly cloudy warm SE TX weather day with isolated to scattered showers and a few thunderstorms while heavy rains remain over S and Central TX. A cool front still expected to drift across SE TX at the end of the week.
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Re: September 2017 - Rain Chances/End Of Month Cold Front

Postby DoctorMu » Wed Sep 27, 2017 11:27 pm

It will be a welcome relief to get the dew point below 70°. The wind is light this time of the year in CLL...so the stuffiness can drag on into the fall.

A chance of rain in CLL Friday night as most of the rain continues to remain west. A short respite during the weekend with drier and slightly cooler air. Before a bounce back Monday in PW/DP. We may not see something that resembles a Fall cold front until about the 10th of October.


PREV DISCUSSION... /ISSUED 248 PM CDT Wed Sep 27 2017/

DISCUSSION...
Radar imagery shows a few showers in Jackson, Wharton, and Matagorda
counties this afternoon, currently over the pocket of higher
moisture as seen on the GOES-16 satellite imagery. Not expecting
much in terms of coverage tonight, but kept widely scattered
showers and thunderstorms in the forecast to continue into the
early evening. Short term guidance such as the HRRR and RAP are
hinting at some isolated shower development in the eastern zones
of the forecast area early Thursday morning. By Thursday
afternoon, PW values increase to 2.00-2.20 inches, so moisture
will be in surplus. Additionally, diurnal heating and lift
provided from both the seabreeze and stationary/ "cool" front as
it sags southward into the region, will provide a better chance
scattered shower and thunderstorm development Thursday. Kept
precip in the forecast for Friday as well, with less coverage in
comparison to Thursday. High temperatures for the rest of the
week will be in the upper 80s to lower 90s, with lows in the mid
60s to upper 70s along the coast.

Besides the possibility of a few isolated lingering showers late
Friday into early Saturday, not expecting much in terms of precip
through the weekend. Weak upper level ridging attempts to build in
behind the frontal boundary. More seasonable weather can be
anticipated Saturday and Sunday with lower dew points, as drier
air ushers in behind the weak front. Temperatures will also be a
tad cooler and closer to normal for this time of year.

With the rise in PWs ranging from 1.40 to 1.70 inches beginning
Monday, a more summer-like pattern will return to the forecast.
Winds will shift back to out of the southeast with the start of the
new week, and as a result carrying scattered showers and
thunderstorms associated with diurnal/seabreeze activity.
Conditions look to dry out by mid-next week as both the ECMWF and
GFS begin to build in an upper level ridge over the region. This
area of high pressure will enhance subsidence (sinking air), so
therefore holding PoPs at 30% or lower through the remainder of
the week. High temperatures will rise into the mid to upper 80s,
with lows falling into the upper 60s inland to upper 70s closer to
the water.

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Re: September 2017 - Rain Chances/End Of Month Cold Front

Postby tireman4 » Thu Sep 28, 2017 8:28 am

000
FXUS64 KHGX 281141
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
641 AM CDT Thu Sep 28 2017

.AVIATION...
VFR early this morning with plenty of mid/high level clouds, especially
out west. Daytime heating should get SHRA/TSRA to develop this afternoon
across SE TX. Activity should weaken this evening with models indicating
some stuff hanging around and/or redeveloping overnight. Winds N to
NE today (5 to 10 knots) becoming N tonight (under 5 knots inland and
5 to 10 knots at the coast). 42
&&

.PREV DISCUSSION... /ISSUED 346 AM CDT Thu Sep 28 2017/

DISCUSSION...
Showers and storms should be more numerous today than the past
couple of days with ample moisture and a few features to support
upward motion in spite of a building upper ridge over the region.
That potential should wind down for the weekend, with drier and
slightly cooler (mainly at night) weather expected. By next week, we
should return to a pattern more akin to the summertime than the
fall, with corresponding daily shower and thunderstorms chances
and temperatures warmer than seasonal averages.

NEAR TERM [Through Today]...
The radar shows a few areas of interest late tonight - the first
is another fairly large mass of rain in Rio Grande Valley and
border region. Though the coldest IR cloud tops are around -88C,
the strongest storms also are further on the Mexican side of the
border, and thus intensity in Texas appears to be less than in
previous nights. Still, some showers appear close to our western
border. To the north of our coverage area, some light showers
(perhaps not even hitting the ground) are present near or just
north of the sagging cold/quasistationary front. Finally, to the
east, a localized area of surface convergence is kicking off
showers near our eastern border - though most are dissipating
before reaching our easternmost counties, an occasional shower
may be dropping a small amount of rain before falling apart.

All three of these features may play a role through the day today
along with any seabreeze feature drifting inland. Precipitable
water at or exceeding two inches in the GOES-16 TPW product, which
is bolstered by continued levels of moisture in the guidance.
Between this, scattered to numerous showers and storms should
erupt this afternoon. Model soundings suggest 500-1000 j/kg of
MLCAPE, in a skinny distribution through a fairly warm and
saturated column. Such a profile suggests potential for locally
heavy rainfall, though the lack of any shear to speak of will
limit updraft longevity and should keep rain totals from getting
too out of hand (key word here being `should`). DCAPE values look
pretty decent, and there`s an inverted-V looking feature in the
lowest portion of the atmosphere as well - this could imply some
gusty winds in the strongest cells, but again with such a weak
wind profile, it seems unlikely that we`d manage any damaging
gusts.

SHORT TERM [Tonight Through Friday]...
As northeasterly flow becomes established overnight, we should
begin to see the first influences of drier, post-frontal air in
the HTP (Houston-Trinity- Polk counties). Without a real solid
push behind the front, and triggering features that aren`t
diurnally driven, I do keep some PoPs in the west through the
night and into Friday morning, though the loss of instability
through heating and no cooling aloft, don`t expect things to be
very vigorous. Expect the eastern bulk of the area to stay dry and
potentially even a couple degrees cooler, while some potential for
showers and storms will linger in the westernmost portion of the
area where PW values continue to exceed 1.75 inches and could
even remain near 2 inches.

LONG TERM [Friday Night Through Wednesday]...
The post-frontal regime really begins to assert itself Friday
night and Saturday, with lows dropping into the lower 60s well
inland (still staying in the lower 70s along the water). Weather
should remain dry through the weekend. However, winds should be
veering from northeasterly to more easterly later Sunday, and
signals the end of the brief reign of more seasonable conditions.
Look for humidity and temperatures (especially at night) to nudge
slowly upwards into the new week.

Easterly to southeasterly winds, increasing in strength thanks to
potential developing low pressure around the Yucatan, will surge
moisture back into the area early next week. PW could even rise to
2.25 inches if the GFS were correct. Perhaps unsurprisingly, the
GFS (and the Canadian, for that matter) is very gung ho on rain
in the first half of the week. The Euro has a similar pattern, but
is not quite as aggressive with the rain. Additionally, GEFS
plumes show the operational GFS is significantly wetter than the
ensemble mean, and only one ensemble member is within a quarter
inch of the op run at IAH - Bush Intercontinental. So, though the
GFS influence on blends push PoPs way, way up in the long range,
I chose to step things down, and go with values in the 30-40
percent range to signal a little better shot than usual for rain.
These probabilities can always be tuned in the coming days if more
confidence in widespread rain emerges. For now, I will shade more
towards the Euro and the ensembles.

MARINE...
Light east winds early this morning will become more east to
northeast and gradually strengthen through Friday night and
Saturday as a weak frontal boundary moves off the coast. Caution
flags might be needed. Winds and seas should come down a little
Saturday night and Sunday. A tightening pressure gradient is
expected to bring strengthening east winds and building seas to
the area next week, and caution flags might be needed once again.
This prolonged easterly flow may cause some minor coastal flooding
issues in the mid to late week time period. 42

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 87 71 85 66 88 / 50 30 20 10 10
Houston (IAH) 88 73 88 68 87 / 40 30 10 10 10
Galveston (GLS) 87 78 87 76 85 / 30 20 10 10 10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

25/42
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