December 2016- End Of Year Forecast

[Electric Lizard]

This morning's NWS disco gets on board with next week's cold by suggesting a bear watch may be warranted soon.

[srainhoutx]

Wednesday morning briefing from Jeff:

Wet weekend for much of the state

Same cold front responsible for the 23 tornadoes overnight in LA, MS, AL of which one struck a 24-hr daycare at 213am this morning completely destroying the structure and critically injuring four children and resulting in 3 nearby fatalities, has pushed off the TX coast allowing a refreshingly dry air mass to overspread the region.

Cold air advection will continue today with temperatures slowly falling this morning into the 50’s across much of the entire area under N winds and a mid level cloud deck. Highs will only reach the mid to upper 60’s today compared to the record breaking mid 80’s on Tuesday. Coldest morning will be Thursday under clear skies and light winds and expect temperatures to fall into the upper 30’s NW to near 50 at the coast.

Friday-Sunday:
While there are still timing differences on when this weekend storm event will begin and end…models remain in good agreement that a very wet pattern will develop over SE TX.

Friday:
An upper level storm system will move from the NW US southward into NW MX and begin to cut off from the main jet stream flow aloft. The deep southern position of the upper level trough will begin to force surface pressure falls along the lower TX coast late Friday. Moisture will rapidly return across TX from both the Pacific and the Gulf of Mexico starting on Friday and we may begin to see showers break out by late Friday afternoon…which is a little faster than the previous thinking. Developing coastal low off the lower TX coast will lock in cold NE surface winds and cold air mass over the region with mid level moisture spreading northward over this surface cold dome.

Weekend:
SW flow aloft on the eastern flank of the NW MX upper level storm system and developed/NE tracking costal trough/low will result in messy conditions for the weekend. Strong overrunning of warm moist air above the surface cold layer will result in widespread rainfall from Saturday morning well into Sunday night and likely into Monday. Rainfall, clouds, and NE wind draining cold air in to the region will keep a near steady temperature through the entire period in the upper 40’s to mid 50’s.

Current thinking is that the coastal trough/low will progress from the lower TX coast late Saturday NE/ENE to off the upper TX coast by early Monday which will bring some marine impacts to winds and possibly tides. This track of the surface features and warm/cold sectors of the storm system favors the maximum rainfall totals to be along the coast and offshore as well as any severe weather threat. Should the surface low track inland or closer to the coast higher rainfall totals and severe weather would need to be added likely for Sunday.

Rainfall Amounts:
Widespread rainfall amounts of 2-4 inches are likely over the next 5 days with most of this falling Saturday and Sunday. Expect the 2 inch totals more inland with the higher totals near the coast and offshore. Could see isolated amounts upwards of 6-7 inches over the coastal waters given forecasted PWS of 1.7-1.9 inches. Certainly the threat for heavy rainfall is there with those kind of PWS values, but current thinking is that the most concentrated convection will remain along and SE of US 59. Should the coastal trough track closer to the coast or slightly inland then rainfall amounts will need to be increased along and S of the US 59 corridor.

5-Day Forecasted Rainfall Amounts:

Cold Air Outbreak:
Bitter cold air mass which has been stuck in Russia and Siberia for much of November has built into Alaska over Thanksgiving where current temperature readings are in the -30F to -40F range. Both the ECWMF and GFS along with several of their ensemble members develop an increasingly amplified upper air pattern next week over the northern Pacific which forces high pressure to build northward toward Alaska and then a deep downstream trough to form over the western US. This is certainly an upper level pattern favorable for delivery of a cold source region (Alaska) arctic air mass southward into the US. Given that the source region is actually fairly cold and expected to remain cold adds support to a significant intrusion of cold air into the plains by the middle to end of next week. [/i]

[srainhoutx]

Some have been asking what the mid December toward Christmas timeframe may offer. The Updated CFSv2 Monthly climate model suggests colder than normal temperatures and slightly above normal precipitation chances. Typically I have noticed a bit of a warm bias for this particular Long Range Ensemble Model over the years. That said look how cold our source Regions of Eastern Alaska and NW Canada throughout the month.

[srainhoutx]

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 AM EST WED NOV 30 2016

VALID 12Z SAT DEC 03 2016 - 12Z WED DEC 07 2016


...OVERVIEW...

ONCE AGAIN...THE MEDIUM RANGE PERIOD (SATURDAY THROUGH WEDNESDAY)
CONTINUES TO BE PLAGUED BY THE UNCERTAINTY OF THE UPPER TROUGH
EJECTING EASTWARD FROM NORTHERN MEXICO. HOWEVER...ENSEMBLES ARE
BEGINNING TO COME TO A CONSENSUS REGARDING ITS EVOLUTION. BY DAYS
6 AND 7...THERE CONTINUES TO BE AGREEMENT AMONGST THE MODELS WITH
THE INCOMING DIGGING TROUGH FROM THE PACIFIC.


...MODEL EVALUATION/PREFERENCES...

THE BIGGEST CHALLENGE IN THE FORECAST ONCE AGAIN IS THE TRACK AND
SPEED OF THE UPPER LOW OVER NORTHERN MEXICO ON SATURDAY. THE GFS
CONTINUES TO HAVE GOOD CONTINUITY WHILE THE 00Z ECMWF BEGAN TO
MIRROR THE OLDER MODEL RUNS OF BEING TOO FAST ALONG WITH THE
ENERGY FROM THE NORTHERN STREAM STACKING ON TOP OF THE CLOSED LOW
OVER MEXICO. THE 00Z GFS AND GEFS BOTH SHOW THE NORTHERN STREAM
QUICKLY PROGRESSING TOWARD THE EASTERN US AS THE UPPER LOW OVER
MEXICO SLOWLY TREKS TOWARD TEXAS OVER THE WEEKEND. HOWEVER...THE
ECMWF ENSEMBLE MEAN BEGAN TRENDING TOWARD THE GFS/GEFS SOLUTION
WITH THE PLACEMENT AND TIMING OF THE UPPER LEVEL LOW AND BY
MONDAY...THE UPPER LOW WEAKENS OVER TEXAS AND TRACKS EASTWARD.
BECAUSE OF THIS...USED A 00Z GEFS/GFS/ECENS BLEND BUT LEFT THE 00Z
ECMWF OUT DUE TO IT REGRESSING BACK TO ITS OLDER TRENDS.

BY DAYS 5 THROUGH 7...GOOD AGREEMENT REMAINS ON THE ENSEMBLES
SHOWING A RIDGE BUILDING ACROSS THE GULF OF ALASKA...WHICH WILL IN
TURN ASSIST IN ANOTHER UPPER TROUGH DIGGING ACROSS THE WESTERN US.
THIS UPPER TROUGH WILL PROGRESSES QUICKLY ACROSS THE CENTRAL US
BY THE END OF THE MEDIUM RANGE PERIOD. MEANWHILE...THE RIDGE WILL
BUILD BACK ACROSS THE WESTERN CARIBBEAN AND SOUTHEAST.


...WEATHER HIGHLIGHTS/THREATS...

THE POTENTIAL FOR HEAVY RAIN ACROSS THE EASTERN HALF OF TEXAS AND
THE LOWER MISSISSIPPI VALLEY REMAINS FOR THIS WEEKEND AS THE UPPER
LOW MOVES OVER THE REGION. AT THE SURFACE...A LOW WILL TRACK
ACROSS THE WESTERN GULF OF MEXICO AND MOVE NORTHWARD ACROSS THE MS
VALLEY. IN ADDITION...VALLEY RAIN AND MOUNTAIN SNOW WILL SPREAD
ACROSS THE PACIFIC NORTHWEST AS A SURFACE FRONT MOVES ACROSS THE
AREA. SNOW WILL CONTINUE ACROSS THIS REGION IN ADDITION TO THE
NORTHERN ROCKIES AS MOIST ONSHORE FLOW CONTINUES UNDER A STRONG
WEST-EAST UPPER LEVEL JET.


EXPECT BELOW AVERAGE TEMPERATURES FOLLOWING NEAR THE CLOSED LOW IN
THE SOUTHWEST/FOUR CORNERS REGION FRIDAY INTO THE SOUTHERN PLAINS
AND SOUTHEAST THIS WEEKEND. AS THE CANADIAN HIGH SPILLS OVER THE
INTERMOUNTAIN WEST BY DAY 6...MUCH COOLER TEMPERATURES WILL FILTER
ACROSS THE WESTERN US...WITH TEMPS 15-25F BELOW THE AVERAGE. THE
EAST WILL SEE A WARMING TREND AS THE UPPER RIDGE BUILDS IN FROM
THE SOUTHEAST.


FANNING

[srainhoutx]

Michael Ventrice ‏@MJVentrice · 21m21 minutes ago  Andover, MA
Big cut-off low to impact the South this weekend could produce some very heavy rains across Texas; Newest ECMWF putting out 3-6" thru Monday

[DoctorMu]

Bullseye on Galveston for the weekend rain.

[srainhoutx]

The afternoon Updated Climate Prediction Center Outlooks for Day 6 to 10 and Day 8 to 14 suggest below normal temperatures will spread across the United States.

[jasons2k]

Euro and GFS sure look different on rainfall placement.

[srainhoutx]

The overnight updated quantitative precipitation forecast and the excessive rainfall outlook suggest we may have some issues across the Eastern half of Texas extending into Louisiana.

[unome]

The overnight updated quantitative precipitation forecast and the excessive rainfall outlook suggest we may have some issues across the Eastern half of Texas extending into Louisiana.

the very soggy day 3

the closed mid level moves slowly east to western mexico during day 3. the low level inflow increases to about 30 knots from the southwest... continuing to funnel 1.75/2.00 inch preciptable water air across eastern tx into portions of la. while there is some spread on the placement of a frontal boundary extending from low pressure over far south tx... the low level moisture and marginal to locally moderate instability becomes focused on the front... increasing the threat for heavy to excessive rainfall. an axis of 2.75 to 3.50 inches of qpf was stretched from the middle tx coast across northern la and far southern ar... where the best instability is expected.

these qpf amounts are lower than the maximum qpf amounts from the 00z gfs (and even the 00z ecmwf). locally higher amounts are possible... as corfidi vectors become better aligned with the mean 850-300 mb flow ahead of the closed mid level system. members of the 00z gefs and 12z ecmwf ensemble output suggest that potential for 4.00+ inch qpf amounts... mainly over the upper tx coast into northern la. three hour flash flood guidance values are generally 2.50 to 3.50 inches... and given some of the qpf amounts from the 00z model suite... as well as the potential for training in a high moisture content airmass... a slight risk area was placed over much of eastern tx... the eastern half of la and southernmost ar for day 3.

[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.