Wx Infinity Forums

Seem like the long range Temps in the five days around Christmas are cooler than average. Seems they have been trending that way...to somebody who really knows...is that accurate?

Very subtle changes with this afternoons guidance. The greatest threat for the late week storm system continues to be the potential for heavy rainfall across portions of Texas and Louisiana. Lighter amounts of rainfall extend from S Central Texas and along the Northern Gulf Coast into Northern Florida and Southern Georgia. In the cold sector, snow freezing rain and sleet are possible across the Texas Panhandle, Oklahoma into Arkansas, Tennessee, Northern Mississippi, Northern Georgia, the Carolinas and Virginia. The forecast appears fairly straight forward as the various computer models have been very insistent for heavy rainfall over the last 5 days or so. Subtle shifts N and S likely will continue until Wednesday and Thursday when the storm system moves inland along the West Coast and when get in range for the short fuse guidance to latch onto the likely progression of the Cold Frontal Boundary. Best guess for rain begins increasing Thursday afternoon/evening across Central Texas and ramps up Friday into Friday night/early Saturday.

Hodographs are looking very impressive across this region Friday night. Cyclogenisis could really pump up the low level jet and create wide sweeping profiles. While available energy is limited, plenty of lift will be provided by the upper level trough. I definitely think straight line winds and even isolated tornadoes could be an issue Friday and Friday night across central and east Texas (including SE Texas).

Do we have a timeframe that the storms will be coming Friday? My daughter will be leaving Galveston and traveling back to Beaumont after her basketball tournament . They will be traveling back Saturday morning to Galveston.

Same thing timing...I have a big move on Saturday. Will this system be early or late to arrive overall?

Samantha550 wrote: ↑Mon Dec 03, 2018 7:40 pm Do we have a timeframe that the storms will be coming Friday? My daughter will be leaving Galveston and traveling back to Beaumont after her basketball tournament . They will be traveling back Saturday morning to Galveston.

SLM87TX wrote: ↑Mon Dec 03, 2018 10:19 pm Same thing timing...I have a big move on Saturday. Will this system be early or late to arrive overall?

Across central and southwest Texas scattered storms will start Friday morning. That will spread to the northeast over the day including SE Texas. A heavier line is likely to form over central Texas by mid evening and will push southeast through the day. As it currently stands, the strongest storms will move through SE Texas between 8pm and 3am. Still need a day or two to narrow down the timing, but current models indicate this will likely be an overnight Friday event. Conditions will improve pretty rapidly after the front moves through Saturday morning.

Tuesday morning weather briefing from Jeff:

A significant storm system will impact the region late this week and early weekend.

An upper level storm system currently located off the west coast of the US will continue to move SE and into the SW US and NW MX over the next 48 hours. Dry air mass over TX will undergo rapid changes starting late Wednesday as winds turn back to the SE and moisture begins to increase. As surface pressures begin to fall early on Thursday moisture will stream into SE TX from the Gulf of Mexico with PWS rising toward 1.2-1.5 inches during the day. Broad large scale lift will begin to advance into central TX Thursday and expect bands of streamer showers to develop from the coastal bend through central TX with some of this activity likely clipping our western counties.

Friday/Early Saturday:

Highly active weather period is likely.

A strong upper level trough over N MX will move eastward into SW TX early Friday and then cross the state into early Saturday bringing strong lift across an unusually moist air mass. Moisture levels on Friday rise to near record levels for early December with PWS of 1.8-2.0 inches being forecasted over the area which is more common in August. Strong dynamic lift from the upper level trough will promote the formation of deepening surface low pressure system over the coastal bend/SE TX by mid to late afternoon into the evening hours. A strong modified arctic cold front will be slowly moving into SE TX during the late afternoon hours on Friday into Saturday. A slow moving boundary, coupled with ample low level inflow, near record moisture levels, and strong splitting jet stream structure are all pointing toward a heavy rainfall event Friday into Saturday morning. Where the heaviest rains fall is still uncertain, but recent WPC guidance is suggesting a large area of 3-5 inches over much of the area with higher amounts likely.

Given the time of year and the fact that an early freeze has already knocked down much of the vegetation over the area along with the already wet ground conditions, rainfall of this magnitude is going to result in significant run-off. Widespread nature of the event strongly supports significant rises on area rivers, creeks, and bayous.

At the moment severe weather looks minimal with a general lack of instability, however parts of SE TX will likely be within the warm sector air mass on Friday afternoon and evening and experience with such events in the cool season along the Gulf coast in the past has resulted in some severe weather will very little instability in play…so this will be something to monitor over the next few days.

Forecasted Rainfall Amounts (Friday-Saturday):

The 12z Euro has anywhere from 2.5 to 6.5” of rain for Friday’s event across southeast TX.

A lot of High School Football playoff games Friday night...I wonder how many delays or cancelations will take place?

CRASHWX wrote: ↑Tue Dec 04, 2018 2:02 pm A lot of High School Football playoff games Friday night...I wonder how many delays or cancelations will take place?

I just posted about this on another site. I’m sure there will be plenty of them. It’s rare to get this kind of rainfall here in December.

Cpv17 wrote: ↑Tue Dec 04, 2018 2:24 pm

CRASHWX wrote: ↑Tue Dec 04, 2018 2:02 pm A lot of High School Football playoff games Friday night...I wonder how many delays or cancelations will take place?

I just posted about this on another site. I’m sure there will be plenty of them. It’s rare to get this kind of rainfall here in December.

Timing and placement will be major factors.

It was chilly today, even out in the sun. At least it's not expected to freeze this week

I'm so ready for summer.

Another chilly morning across SE TX. Changes begin tomorrow with a marginal risk area of severe storms across S TX. Heavy rain will be the concern across SE TX Friday night into Saturday morning with 2-5” however some isolated totals up to 10” will be possible.

Wednesday morning weather briefing from Jeff:

A significant storm system will bring high impacts to SE TX Friday and Saturday

Widespread heavy rainfall and flooding increasingly likely

A strong storm system currently off the CA coast will move offshore today and into the SW US/NW MX tonight into Thursday and then arrive into TX on Friday into Saturday. Surface high pressure is starting to move eastward this morning and winds will return to the SE later today and begin to advect moisture into the area. Clouds will rapidly increase from west to east late today and tonight and expect mostly cloudy conditions on Thursday. A weak short wave will eject out of the trough and across TX on Thursday and this feature combined with deepening moisture levels will likely result in streamer showers from the coastal bend NNE across C TX and into our western counties by the afternoon hours.

Friday-Saturday midday:

Significant weather event increasingly likely.

Strong trough will begin to move into TX with both a surface cold front and surface low pressure system arriving across SE TX Friday evening. Moisture levels are still forecast to rise to near record or even exceed record levels by Friday evening with the advancement of two source streams over the area from the deep southern Gulf and the eastern Pacific. PWS are forecasted to rise to near 2.0 inches which for early December is near the maximum values. In fact a review of Lake Charles historic PW plots indicates that the highest early December value ever record was 1.98 inches and for Corpus Christi 2.07 inches. The maximum moving average for Lake Charles for this time of year is around 1.8 inches and the 90% average is 1.35 inches…to put is simply there is going to be excessive amounts of moisture in place that is fairly uncommon during this time of the year.

In additional to the deep tropical moisture profile, a slow moving SW to NE oriented frontal slope which will be nearly perpendicular to the upper level winds from the SW will be crossing the area and a surface low pressure system will likely form somewhere in/near SE TX. A low level jet of 45-55kts will develop from the TX coast bend into SE TX Friday afternoon and support both strong moisture and temperature advection across the region. Low level inflow will become maximized early Saturday morning over the region with the formation of the surface low. Upper level divergence will increase with the trough progressing into SW TX late Friday helping vent convective elements. All of these ingredients point toward a widespread heavy rainfall event.

Rainfall Amounts:

Widespread rainfall amounts of 3-5 inches are likely with significantly higher totals of 6-9 inches under sustained training bands. While it is still uncertain where the heaviest rains will fall, some of the latest global model guidance and the longer term short range guidance is starting to favor area along and N of US 59 for the heaviest axis of rainfall. Interestingly the CMC model has been fairly consistent in its axis of very heavy rainfall from about I-10 NNE toward the Lake Livingston area, while the GFS continues to favor areas just north of our area. For consistency, the GFS continues to produce a point rainfall for IAH of over 3.0 inches for this event.

Hydro:

Grounds are fairly wet over the region given both the time of year and recent rains in October with KBDI values of 0-200 across much of the eastern half of TX and 6-hr flash flood guidance values of 4.5 inches for Harris County. Since the area has already experienced an early season killing freeze, most vegetation is dead or dormant which is leading to little to no soil evaporation. Given the expected widespread nature of the rainfall totals, significant rises on area rivers, creeks, and bayous is becoming likely with this event and some locations may reach or exceed flood stage. Additionally, high rainfall rates with convective elements support local street flooding conditions in urban areas.

I want to be clear that rainfall of these amounts this time of year will have a significantly different response on area watersheds than during the warm season months…a more run-off will be generated.

Decision Support:

Timing: Friday afternoon-midday Saturday
Rainfall Totals: 3-5 widespread, 6-9 isolated
Location: heaviest rainfall likely will focus along and N of I-10, but this remains in flux
Confidence: event confidence is high, location is heaviest rainfall remains low to moderate

Forecasted Rainfall Totals (Friday-Saturday): Excessive Rainfall Outlook (Friday): [/i]

That’s a lot of heavy rain over a large area. Rivers and creeks will fill-up quickly so keep an eye out.

30 degrees in Central Hardin County this morning...not much frost...guessing thee dew point was mid 20’s?

Where cyclogenisis occurs will likely be key for the heavy rainfall placement this rain event. While upper level moisture and lift will be available across all of the state, how far the warm front lifts north and low pressure forms will likely dictate where the heaviest totals occur. Currently the GFS has been shifting this further and further south across South Texas. The NAM takes it over central and SE Texas and the ECMWF takes it across Bryan. Having that low level jet ramp up will pool a lot of moisture into the region where it does form.

Will we have high winds with this?