January 2021

[Cromagnum]

All the forecasts I've seen have my area 10 degrees too high for anything to freeze. Just going to be cold and nasty.

[Stormlover2020]

Models as of now are coming in little colder so that’s a good sign

[Cpv17]

Follow the NAM 3km model for temps. It’s usually pretty accurate.

[tireman4]

000
FXUS64 KHGX 081051
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
451 AM CST Fri Jan 8 2021

.SHORT TERM [Today and Tomorrow/Saturday Night]...

With wrap around clouds dissipating/moving out, mostly sunny to
sunny skies should prevail today as generally light north winds
persist. Highs today and tomorrow will be in the 50s. Low temp-
eratures could fall to around freezing overnight tonight across
northern portions of our CWFA...ranging around the mid 30s over
the central counties and mid 40s along the immediate coast. For
tomorrow night, as winds become more easterly (but still light)
and clouds begins to increase from the west, overnight lows are
expected to be warmer: from the upper 30s to lower 40s north...
mid to upper 40s central and south...around 50s at the coast.
41

&&

.MID TERM [Sunday through Monday Night]...

By early Sunday morning, base of upper level trof should be situated
across southeastern NM and far west Tx and a coastal low will be in
the process of developing between the middle Tx coast and Matagorda
Bay. Look for rain to spread across the region from west-to east
during the morning hours with increasing large scale lift as both
features make further eastward progress. Majority of the 00z model
runs show a slightly warmer atmospheric temp profile during the
daytime Sunday, and assuming this holds...precip should remain in
liquid form across the vast majority of the CWA during the daylight
hours. May need to keep an eye out for some locally heavy rainfall
across portions of coastal Jackson, Matagorda and Brazoria Counties
in association with the developing coastal low & enhanced llvl
convergence in that general vicinity.

Heading into the early evening hours, temp profiles & thickness
values become more supportive of mixed precip or perhaps a
changeover to frozen precip across northern parts of the
CWA...eventually sagging southward overnight. That said, guidance
isn`t showing quite as impressive frontogenesis as some of the
previous runs and moisture levels in the -10 to -20C zone also begin
to diminish as the system begins to move out overnight. Still like
the general outlooked areas we`ve been advertising (but maybe lower
totals): Highway 105 & northward seeing the better chances of seeing
some accumulating snow & perhaps some lighter mixed precip and much
lower chances of any significant accumulations to I-10. This of
course is based on the latest data we`re looking at...and it`s bound
to change with time. Slight deviations with the tracks of the upper
trof & coastal low position can make a world of difference.

Precip should be done by Monday morning with cloudy, cold and breezy
conditions prevailing for the remainder of the day. 47

&&

.LONG TERM [Tuesday through Friday]...

Despite the NE track of the upper low, the upper pattern seems to
be keeping a lingering trof axis anchored west of the state. This
weak trof is forecast to deepen and the subsequent development of
another closed low (around mid week or so) will keep a persistent
southwesterly flow aloft in place over SE TX through the week. As
we have seen in the past, this pattern does appear to favor a lot
of mid/high clouds and low POPs (via the embedded shortwaves rid-
ing around the base of the upper trof/low). Not sure we will have
enough moisture to support this at this time, so will keep things
dry/quiet but warming for the extended portion of the forecast.
41

&&

.MARINE...

SCEC conditions continue for the offshore 20-60nm Gulf waters. High-
res model guidance shows winds maintaining at 15 knots through the
morning hours on Friday, so the SCEC has been extended to 15z. A Low
Water Advisory is also in effect for Galveston Bay as water levels
are already around 0.5 ft below MLLW due to the strong offshore
winds. With low tide later this morning, the water levels are
expected to drop down to just over a foot below MLLW. The offshore
winds will continue through Saturday afternoon before turning more
easterly. As a result, seas are expected to increase to 8-10 feet
heading into the latter half of the weekend ahead of the development
of a coastal low. As the low approaches the region, SCA conditions
are expected throughout the day on Sunday and into Monday afternoon
as winds start off as easterly/southeasterly around 20-25 knots
before transitioning to northerly around 25-30 knots following the
passage of a cold front on late Sunday. The strong offshore winds
and elevated seas will last through Monday afternoon. 26

&&

.AVIATION [12Z TAF Issuance]...

A cloud deck bringing near MVFR conditions continues to stretch
across the eastern portion of the area. Looking at satellite
imagery, it appears that the clouds will make it further south
than initially anticipated. Weak northwesterly winds remain in
place for all inland airports with GLS still receiving occasional
20+ knot wind gusts due to its steep low-level lapse rates. The
other airports have steep lapse rates as well, but are inhibited
by a surface inversion. As far as cloud cover goes, NAM/HRRR are
in agreement that clouds around 2,500-3,000ft will stick around
into Saturday afternoon so the 12z TAFs will lean in that
direction. 26

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 53 34 53 40 43 / 0 0 0 10 90
Houston (IAH) 55 38 55 42 45 / 0 0 0 10 90
Galveston (GLS) 55 46 54 49 53 / 0 0 0 10 90

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...Low Water Advisory until 6 PM CST this evening for the following
zones: Galveston Bay.

&&

$$

Discussion...99
Aviation/Marine...99

[tireman4]

This is an everchanging situation. As we continue into the weekend, more will come into focus...this is from the HGX AFD..

Still like
the general outlooked areas we`ve been advertising (but maybe lower
totals): Highway 105 & northward seeing the better chances of seeing
some accumulating snow & perhaps some lighter mixed precip and much
lower chances of any significant accumulations to I-10. This of
course is based on the latest data we`re looking at...and it`s bound
to change with time. Slight deviations with the tracks of the upper
trof & coastal low position can make a world of difference.

[don]

From Jeff Lindner:

A powerful winter storm will impact much of TX this weekend.

Main focus is on the Sunday-early Monday period as a powerful upper level storm system and coastal surface low move across the region bringing various weather types to the area.

Upper level trough currently just off the Oregon coast will move inland today and then drop SSE into the Great Basin on Saturday before ejecting eastward across TX on Sunday. As this trough approaches TX this weekend, coastal surface pressure will lower and a surface low will form in association with the strong ascent that will come to bear over coastal area on Sunday. This surface low will quickly deepen and move generally ENE/E from near Matagorda Bay on Sunday with strong winds developing over the coastal waters. The surface low will also push moisture NW into a deepening cold air mass associated with a cold front that forms under the upper level trough that will move across central and north Texas.

Set Up:
Incoming upstream air mass is not overly cold for this time of year and is more Canadian in origin than Arctic, in fact most of the area will likely remain above to well above freezing well into Sunday evening and it is the lowest few thousand feet of the air mass which is causing all the issues with the potential precipitation type over the area. It will likely be cold enough for snow to form in the higher levels of the atmosphere, but then melt as it falls through the warm layer near the surface. As the upper level cold pocket associated with the upper level trough moves closer to the area on Sunday evening, this warm layer in the lower atmosphere begins to shrink from the top toward the surface. The more this warm layer shrinks, the more snow aloft will begin to reach the ground and mix with rain or transition to snow. Strong lift can also help cool the column of air and some of the models are showing some mesoscale banding of the precipitation and strong precipitation bands which can help locally cool the air mass and allow snow to reach the ground and accumulate due to the increase in the precipitation rates and the pulls of the cold air toward the surface. One would also look for any near surface dry air that can be evaporated to help cool the lower atmosphere…this is looking unlikely in this event as much of the air column looks to become saturated on Sunday.

Forecast:
Think most of the area will start out as rain on Sunday morning and likely remain rain for much of the day. Track of the coastal surface low could result in some moderate to at times heavy rains across the coastal counties on Sunday afternoon and given the soggy grounds in place will need to watch for any run-off issues. As the air column begins to cool Sunday late afternoon into the evening rain will likely begin to mix with snow north of HWY 105 and then potentially become all snow by late evening. Between HWY 105 and I-10 rain could mix with snow late Sunday evening, but this area is much more marginal as it is just south of the track of the upper level cold pocket and south of I-10 expecting all precipitation to remain all rain.

North of HWY 105:
Transition to rain/snow mix then all snow Sunday evening. Some accumulation is possible especially on grassy surfaces and elevated surfaces. Accumulations will be strongly tied to snowfall rates…with heavier rates resulting in maybe a dusting to 1-2 inches of accumulation. Bridges and overpasses in this area may have some concerns late Sunday evening into Monday morning.

HWY 105 to I-10:
Rain/snow mix is possible Sunday evening. Accumulation at this time is not likely

South of I-10:
Precipitation is expected to remain all liquid

Confidence:
While there is increasing confidence, the exact locations of precipitation type, possible accumulations, and impacts remain on the lower side. Any slight deviation of the surface and upper level lows will result in differing forecast for the area and shifting of the current forecast lines. With the upper level system just now entering the upper air network along the US west coast and becoming sampled by this network, better data of this feature will be ingested into models runs later today and early Saturday to help increase forecast confidence.

[Kingwood36]

So basically its a wait and see and watch the radar light up when the time comes

[redneckweather]

More times than not, Highway 105 is the battleground for wintry precip in our part of the world. I live just south of 105, about a 10 minute walk. Hopefully model guidance comes in a little cooler today and tomorrow so a bigger area will have a chance of seeing some of that white stuff them northerners call snow.

[tireman4]

This will change ( as Travis and Jeff have stated) today into the weekend. It will move..maybe with each model run. Stay vigilant.

[don]

I will say i like the trend of some of the 12z models so far, a few have trended colder.

[MontgomeryCoWx]

The latest NAM run...let's lock it in and call it a day.

20210108_085008.jpg

That heavy band axis is where I think the biggest totals will fall. Athens to Henderson and south to Lufkin.

[Stormlover2020]

Yep, we just need that trend to continue.

[DoctorMu]

So basically its a wait and see and watch the radar light up when the time comes

aka Nowcasting. That's the way it was in 2017. Timing of the cold core and robustness of the precipitation to knock out that warmnose are major determinants. The heavy precipt in 2017 allowed for a rapid transition into snow.

We shall see.

[Cpv17]

The Euro looks really good for our northern counties.

[Seantx81]

I will say this... I was in Atlanta for the mayhem that was Snowocolypse and all of the meteorologist there were certain based on models that nothing would happen. The snow started earlier in the day from transitioning from light rain. It started to stick once wet bulbing took over. It got heavier and heavier and in a few hours everything was covered in either ice or snow.

What I'm getting at is two things: 1) these situations are very unpredictable and 2) that wet bulbing always seems make a huge difference in these scenarios.

[AtascocitaWX]

I will say this... I was in Atlanta for the mayhem that was Snowocolypse and all of the meteorologist there were certain based on models that nothing would happen. The snow started earlier in the day from transitioning from light rain. It started to stick once wet bulbing took over. It got heavier and heavier and in a few hours everything was covered in either ice or snow.

What I'm getting at is two things: 1) these situations are very unpredictable and 2) that wet bulbing always seems make a huge difference in these scenarios.

That would be a Awesome thing if that could happen here.

[Stormlover2020]

Nam new run -https://www.tropicaltidbits.com/analysi ... cus_26.png

[tireman4]

Winter Storm Watches Hoisted North of Our Area...( Can change)

[TexasBreeze]

The NAM looks much better now. Back to what it showed early yesterday. Trending right. Seems like not having Montgomery county in the watch is hedging bets towards the lackluster gfs model.

[srainhoutx]

So there's a chance for wintry mischief not too far N and W of Metro Houston?! I see the NAM being mentioned. That meso lending short range model does do a decent job with temperatures, but watch those precipitation projections as the NAM tends to be too aggressive with its totals. Also remember that the Tropical Tidbits snow algorithm does not differentiate between snow/freezing rain/sleet. Fingers crossed for you folks. I've been shoveling snow this afternoon!