December 2016- End Of Year Forecast

[Katdaddy]

The SPC also has a marginal risk area across the Middle TX Coast and SW portions of SE TX on Saturday.

[srainhoutx]

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.

[srainhoutx]

Michael Ventrice ‏@MJVentrice · 19m19 minutes ago
Looking at -25F below average surface temperatures across many locations in the interior West. Models locked on.

[srainhoutx]

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):

The attachment 12012016 Jeff 1 untitled.png is no longer available

[tireman4]

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

[DoctorMu]

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.

[jasons2k]

Indeed. Looks like a great weekend for some indoor projects.

[srainhoutx]

The afternoon updated Climate Prediction Center Day 6 to 10 Outlook as well as the Day 8+ Analogs look very chilly.

[srainhoutx]

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.

[srainhoutx]

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.

[christinac2016]

Well guess I will use this cold and wet weekend to bake and put up the tree. Hoping to get the grocery shopping done before a deluge comes.

[Andrew]

This weekend trend is turning wetter with an estimated 3-6inches widespread with isolated locations of 6-8 inches possible. The coastal lows looks to come closer to shore/onshore which should help increase estimates further inland.

The biggest change in models is the growing consensus that we will see our first freeze (most if not all of SE Texas) late next week. Models are doing a much better job at funneling the colder Arctic air south instead of eastward so quickly. Looks like dewpoints could reach the teens and with proper clearing (high pressure is expected to be nearly overhead) temps in the upper 20s to low 30s seem likely.

[MontgomeryCoWx]

GFS keeps us cold through the following week.

Crazy Canadian drops is into the lower 20s

[srainhoutx]

The overnight guidance has trended wetter for our weekend storm system. The Weather Prediction Center 5 Day quantitative precipitation forecast continue to increase. There is a Moderate Risk for Excessive Rainfall Saturday with a Slight Risk outlined for Sunday. Flash Flood Watches may be hoisted later today if the trends continue. Stay tuned!

[unome]

http://www.wpc.ncep.noaa.gov/index.php#page=ero

because of the tight cape gradient along-just offshore the gulf coast...will continue to be more conservative with the inland extent of the >1.00 inch 24 hour amounts...as expect some degree of obstruction.

I don't want to see their "not conservative" qpf...

[srainhoutx]

Regarding the sharp 'Blue Norther' expected to arrive next Wednesday/Thursday, the overnight ensemble guidance continues to advertise the coldest air of the season will spread across Texas. Potential is slowly increasing that we may see freezing temperatures all the way to the Coast overnight next Thursday/Friday morning. Some inland locations may approach the Hard Freeze threshold if the trends continue. Stay tuned for further updates as we get closer to that news worthy weather event.

[Katdaddy]

A busy weather weekend on the way before next week's "Blue Norther" arrives. Coastal Flood Advisory in effect through Saturday morning. Expect Flash Flood Watches to be issued for SE TX as well later this morning.

COASTAL HAZARD MESSAGE
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
436 AM CST FRI DEC 2 2016

...ELEVATED TIDES THIS AFTERNOON THROUGH SATURDAY MORNING...

.ELEVATED EASTERLY WINDS WILL RESULT IN INCREASING TIDE LEVELS
FOR EAST FACING BAY AND GULF SHORELINES FROM FRIDAY AFTERNOON
THROUGH SATURDAY MORNING. WATER LEVELS WILL LIKELY EXCEED 3 FEET
BY THIS EVENING... WITH MAXIMUM WATER LEVELS NEARING 4 FEET DURING
HIGH TIDE TIMES.

TXZ213-214-237-238-031200-
/O.UPG.KHGX.CF.A.0002.161202T1800Z-161203T1200Z/
/O.NEW.KHGX.CF.Y.0008.161202T1800Z-161203T1200Z/
BRAZORIA-CHAMBERS-GALVESTON-HARRIS-
436 AM CST FRI DEC 2 2016

...COASTAL FLOOD ADVISORY IN EFFECT FROM NOON TODAY TO 6 AM CST
SATURDAY...

THE NATIONAL WEATHER SERVICE IN HOUSTON/GALVESTON HAS ISSUED A
COASTAL FLOOD ADVISORY...WHICH IS IN EFFECT FROM NOON TODAY TO
6 AM CST SATURDAY. THE COASTAL FLOOD WATCH IS NO LONGER IN
EFFECT.

* COASTAL FLOODING...WATER LEVELS OF BETWEEN 3.3 FEET TO AROUND
4 FEET WILL CAUSE COASTAL FLOODING ALONG EAST FACING
SHORELINES.

* TIMING...FRIDAY AFTERNOON THROUGH SATURDAY MORNING.

* IMPACTS...GULF AND BAY WATERS WILL OVERCOME DUNES AND POSSIBLY
OVERWASH PORTIONS OF HIGHWAY 87 ON THE BOLIVAR PENINSULA...AS
WELL AS SECTIONS OF THE BLUE WATER HIGHWAY IN BRAZORIA COUNTY.
LOW LYING ROADWAYS...SUCH AS TODDVILLE ROAD IN SEABROOK...MAY
ALSO EXPERIENCE MINOR FLOODING.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A COASTAL FLOOD ADVISORY INDICATES THAT ONSHORE WINDS AND TIDES
WILL COMBINE TO GENERATE FLOODING OF LOW AREAS ALONG THE SHORE.

[srainhoutx]

Friday morning briefing from Jeff:

Significant rainfall event this weekend….some flooding possible

Coastal Flooding likely this afternoon into Saturday morning

Discussion:
Factors will be in place by late this afternoon to produce a prolonged rainfall events over SE TX this weekend into Monday. A powerful upper level storm system will slowly approach TX today and moisture return is already well under way with mid level moisture pouring into the state from the SW and low level moisture starting to return from the Gulf. Will be watching closely as the coastal trough forms later today on its exact position as this will likely determine where at least one major band of excessive rainfall develops…as early as this evening. Models are all over the place with respect to banding of rainfall and where and breaks if any between large rounds…so will be broadbrush the potential for the entire period from this afternoon through midday Monday. Heavy rainfall will be possible at any time during that period.

Coastal low looks to track up to coast and into SE TX late Sunday along with main dynamics of the upper level system moving across TX at the same time. Warm sector air mass will likely move inland over portions of the area and bring with it a severe weather risk. This is looking more and more like a cool season low CAPE/high shear severe weather threat which can produce low topped supercells. Still fairly far out in time to be certain, but the Sunday night and Monday AM period will need to be watched closely.

Main threat will certainly be the heavy rainfall potential.

Rainfall:
Overall QPF numbers have been increased over the last 24 hours and with widespread amounts of 5-6 inches likely across the entire area and isolated totals of 8 inches or higher. Overnight WPC has increased their 5 day totals to over 9 inches over SE TX which is very concerning given that most of this will fall tonight-Sunday night over in about a 48 hour period. While grounds are dry, rainfall of this magnitude is going to result in considerable run-off and significant rises on area watersheds. Main focus will be along the coastal trough which looks to establish just inland of the coast and possibly along a 850mb front draped over our northern counties.

High moisture levels will certainly support high hourly rainfall rates of 1-3 inches and this will result in street flooding in urban areas.

Flash Flood Watches will likely be required over the weekend.

Tides:
Increasing ENE winds are pushing water toward the coast and coastal flooding is likely this afternoon and overnight. Expect total water levels of 3.5-4.0 ft by late this afternoon which will produce overwash on Bolivar and on the east facing shorelines within Galveston Bay. 4.5 ft is the critical elevation within Galveston Bay to start resulting in widespread coastal flooding…and at this time do not think the tides will get that high…but close.

5 Day Forecasted Rainfall Totals:

[srainhoutx]

The morning Updated CPC GEFS Super Ensembles suggest a very cold pattern may develop with the memorable December 1989 Analogs year appearing a couple of times. Notice the red lines indicating very high heights or Higher Pressures. The chart is indicating High pressure in Eurasia and Siberia with a cross Polar flow into the Western half of North America. The blue shades or line are lower pressures.

[snowman65]

Sure wish I could read that map