December 2016- End Of Year Forecast

General Weather Discussions and Analysis

Re: December 2016- Cold/Rainy Weekend. Tracking Arctic Air

Postby Katdaddy » Thu Dec 01, 2016 6:46 am

The SPC also has a marginal risk area across the Middle TX Coast and SW portions of SE TX on Saturday.
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Re: December 2016- Cold/Rainy Weekend. Tracking Arctic Air

Postby srainhoutx » Thu Dec 01, 2016 7:31 am

While we wait for the stormy weather this weekend, the overnight ensemble guidance continues to advertise the first big shot of Modified Arctic air of the Winter season arrives next Wednesday/Thursday across Texas. The GEFS is about 12 to 18 hours faster with our 'Blue Norther' than the ECMWF EPS. Chances appear to be increasing that a large portion of SE Texas may see the first area wide freeze.
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Re: December 2016- Cold/Rainy Weekend. Tracking Arctic Air

Postby srainhoutx » Thu Dec 01, 2016 8:02 am

12012016 Mike Ventrice Cyl2k9WWIAEXNcw.jpg

Michael Ventrice ‏@MJVentrice · 19m19 minutes ago
Looking at -25F below average surface temperatures across many locations in the interior West. Models locked on.
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Re: December 2016- Cold/Rainy Weekend. Tracking Arctic Air

Postby srainhoutx » Thu Dec 01, 2016 8:07 am

Thursday morning briefing from Jeff:

Widespread heavy rainfall event this weekend.

Factors will rapidly come together to produce a prolonged rainfall event…some of the rainfall will be heavy.

A powerful upper level storm system currently moving toward NW MX will dive southward and then stall over NW MX Friday resulting in extensive downstream moisture return over TX on Friday. Models have sped up the timing of the incoming rain Friday evening and will insert 30% for Friday afternoon and then ramp to 70% Friday night and hold 80% through Monday. As discussed yesterday the formation and position of the coastal trough off the TX coast will make a large difference on where the heavy rains fall…and as somewhat feared model guidance has been trending to back this trough now inland over SE TX and along a line from near Freeport to Houston. This actually may bring the SE 1/3rd of the area into the warm sector with a severe and tornado threat Sunday night/Monday.

With the coastal trough now forecasted to progress more inland this will bring the threat for training heavy rainfall inland also. Will bump QPF numbers into the 4-5 inch range for much of the SE 1/3rd of the region with isolated amounts of 7 inches possible. May see two more distinct rounds of rainfall…the first Friday night into much of Saturday with the formation of the coastal trough and strong overrunning of the surface cold dome…then a slight break early Sunday…followed by the actual crossing of the upper level system late Sunday into Monday which will likely bring the most intense round of weather.

Review of flash flood guidance and NASA soil moisture satellite product shows fairly dry soil conditions over the area with 6-hr flash flood guidance over 4 inches and soil moisture around 25-35%. Think the rains Friday and Saturday will be handled and mainly go into saturating the soil. Bigger concern will come Sunday into Monday as soils become saturated and increasing run-off. This time will also feature the highest potential for excessive rainfall rates as the warm sector air mass moves inland and convection becomes more organized and sustained.

A Flash Flood Watch may be required at some point for all or portions of the area over the weekend.

Temperatures will be fairly steady in the 50’s for much of this period…the exception will be where the coastal trough moves inland and south of this boundary temperatures could easily warm into the 70’s.

Extended:
Much focus on the next 72-96 hours currently….but strong cold front looks in order still mid next week with potential area wide freeze event by late next week.

5 Day Forecasted Rainfall Totals (600am Today-600am Tuesday):

12012016 Jeff 1 untitled.png

12012016 Jeff 2 untitled.png
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Re: December 2016- Cold/Rainy Weekend. Tracking Arctic Air

Postby tireman4 » Thu Dec 01, 2016 9:58 am

HGX AFD this morning

000
FXUS64 KHGX 011124
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
524 AM CST Thu Dec 1 2016

.DISCUSSION...
The cold/dry morning should give way to perhaps our last quiet wx
day...especially when compared to the upcoming forecast for these
next several days. Models remain in generally good agreement with
the prospects of periodic episodes of rain developing across much
of SE TX starting tomorrow (spreading from the SW) on through the
weekend. Low-level moisture progged to increase dramatically with
the strengthening onshore winds tomorrow...in response to the up-
per trof that will begin to deepen near the California Baja. This
system is expected to close off to a rather discrete upper low as
it moves east across northern Mexico into South Central TX on Sat.
An increasingly deep SW flow aloft will help to draw disturbances
across the state via the upper jet to help fuel widespread shower
activity. Rainfall could be further enhanced Sat/Sat night with a
coastal surface trof developing near/just off the lower/middle TX
coast. Very high PWs associated with this system (1.8"-2.0") will
be a concern regarding the potential for heavy rains. However the
heavy rain threat will likely be highly dependent on the track of
this coastal trof. And then to top it all off there is the poten-
tial for storms Mon as the main upper low moves across the region
(with a slight negative tilt and favorable upper jet position).

Perhaps a bit of a break from the rain on Tue, but the prevailing
SW flow aloft (with the longwave trof axis still to our west) may
help to keep some clouds in the area. Extended guidance indicates
a return of low POPS as a rather strong cold front sweeps through
next Wed/Thur. 41

&&

.MARINE...
NNE-NE winds this morning should gradually come around to the east
as high pressure over SETX drifts into LA. Seas should drop slightly
before beginning to build again as gradient tightens Friday. Over
the weekend pressures fall along the South Texas coast and moderate
to strong easterly flow forms with another round of hazardous seas
developing. Easterly flow will encourage higher tide levels and
increasing seas with runup should aggravate tide levels further.
SCEC/SCA conditions should be on tap Friday through Monday. Strong
thunderstorms over the coastal waters also a good possibility with
impressive shear and greater instability. Eventually (depending on
speed of the low`s departure) dry westerly flow wraps around the
system as it swings out to the east Monday or Monday night. Track of
the low will also dictate the location of the stationary/warm front
with it either onshore or over the nearshore waters Sunday and
Sunday night.
45
&&

.Aviation...
VFR with winds veering from light NE to E today. Some patchy fog may
be possible around LBX Friday morning. Over the weekend most sites
will be experiencing an extended period of low cigs/reduced
visibility and a mix of rain/showers/thunderstorms and enhanced
easterly winds.
45
&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 65 46 65 53 58 / 0 10 30 70 80
Houston (IAH) 67 47 64 55 65 / 0 10 30 70 80
Galveston (GLS) 65 58 70 66 68 / 0 10 50 70 80

&&

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

$$

Discussion...99
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Re: December 2016- Cold/Rainy Weekend. Tracking Arctic Air

Postby DoctorMu » Thu Dec 01, 2016 10:03 am

Conroe had its second freeze of the year this am with a low of 31°F.

CLL got some frost - mid 30s IMBY.

Upper 30s for IAH. First freeze of the season for IAH and HOU likely in one week.



Jason - you're getting wet this weekend.
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Re: December 2016- Cold/Rainy Weekend. Tracking Arctic Air

Postby jasons » Thu Dec 01, 2016 12:29 pm

Indeed. Looks like a great weekend for some indoor projects.
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Re: December 2016- Cold/Rainy Weekend. Tracking Arctic Air

Postby srainhoutx » Thu Dec 01, 2016 3:39 pm

The afternoon updated Climate Prediction Center Day 6 to 10 Outlook as well as the Day 8+ Analogs look very chilly.
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Re: December 2016- Cold/Rainy Weekend. Tracking Arctic Air

Postby srainhoutx » Thu Dec 01, 2016 4:04 pm

The afternoon updated quantitative precipitation forecast suggests rainfall amounts may approach 8 inches across portions of Matagorda, Jackson and Brazoria Counties and possibly near West Galveston Bay.
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Re: December 2016- Cold/Rainy Weekend. Tracking Arctic Air

Postby srainhoutx » Thu Dec 01, 2016 4:36 pm

12012016  Ryan Maue CynsONfXgAAxP7R.jpg

Ryan Maue ‏@RyanMaue · 18m18 minutes ago
CONUS average low temp of 17°F for Dec 8th according to ECMWF 12z is exceptionally cold -- there will surely be record lows.

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