Marine Weather and Tide Forecast for Iowa, LA

SYNOPSIS
Issued at 418 PM CST Mon Jan 20 2025

***RARE AND SIGNIFICANT WINTER STORM TONIGHT INTO TUESDAY*** ***DANGEROUS COLD TEMPERATURES AND WIND CHILLS THROUGH THE WEEK***

Potent winter storm system taking shape near the S TX coast where a forming surface trough is progged to strengthen over the coming hours. Moisture continues to increase and deepen in the 850-700 mb layer amid increasing lift, yielding a midlevel cloud deck that has been steadily spreading northward over the area. Aloft, shortwave energy over the SW states is beginning to drop into the base of a longwave trough that encompasses the CONUS, and this energy will provide the support needed for what looks to be a fairly robust winter storm across the region tonight into Tuesday. Northeasterly winds have been strengthening and becoming more gusty in response to the developing surface trough. While temperatures have managed to climb above freezing across the area, the increasing cloud cover has limited "warming", and no sites have reached 40 degrees as of this writing.

A summary of the latest headlines:

- Cold Weather Advisory from 6 PM this evening to 6 PM Tuesday for wind chills down to 12 to 16 degrees

- Extreme Cold Watch from Tuesday evening through Wednesday morning for wind chills between 5 and 15 degrees

- Winter Storm Warning with a light mix of precipitation transitioning to mainly snow overnight. Snow accumulations of up to 2 inches are expected from the Lakes region of southeast Texas into central Louisiana, with 4 and 8 inches across much of southwest and south central Louisiana and southeast Texas, especially along the I-10 corridor. Sporadic ice accumulations of up to 0.1 inch are also possible.

- Small Craft Advisory and Gale Warning in effect for the coastal waters zones for strong winds and hazardous seas.

24

SHORT TERM
(Tonight through Wednesday night)
Issued at 418 PM CST Mon Jan 20 2025

What a time for a first shift back on the forecast desk after being off of it for over a week. Quite a busy next 24 to 36 hours as the low system over the western Gulf interacts with deepening moisture and lift augmented by the approaching shortwave from the west. While this would normally favor increasing rain and possibly a few showers or storms over the area, an arctic airmass entrenched across the area has created a much more complex scenario. Air temperatures are expected to remain above freezing through mid-evening, with onset of precipitation expected across SE TX around the same time. Forecast soundings show a warm nose evident around 700 mb, with profiles mostly below 0C. Any slight adjustments to this warm nose and this would impact p-types at the surface. At this point, a mix of types are expected with precip onset this evening, with a brief window for flurries as well as some freezing rain or ice pellets across SE TX. Precip will likely transition to all snow overnight across the northern zones, while a wintry mix develops across lower SE TX into SW LA after midnight.

As the surface low progresses east across the Gulf of Mexico overnight into Tuesday morning, colder air will begin to spread south into the region, allowing all precip to transition to snow over inland areas. There is the potential for some banding to set up by Tuesday morning, especially along and south of the I-10 corridor, and this could lead to periods of heavy snow along with localized higher accumulations. At this time, general accumulations of up to 2 inches will be possible across interior SE TX into central LA, while further south accumulation of 4 to as much as 8 inches are expected.

Precipitation should quickly come to an end during Tuesday afternoon from NW to SE across the area as the shortwave trough pivots across the region. This will introduce a reinforcing arctic high across the area which will bring extremely cold temperatures and dangerous wind chills to the area. The Extreme Cold Watch will likely be upgraded to a Warning within the next couple of shifts.
The cold temperatures will be exacerbated by clear skies and lightening winds as the high center settles over the area, as well as the lingering snowpack on the ground. Temperatures Tuesday night are expected to falling into the teens across the entire area, with apparent temperatures falling as low as the single digits.

Unusually cold temperatures will linger through the day Wednesday and into Wednesday night. Temperature distribution will be dependent how much snow remains and where the deepest snow will be located as the snow will reflect much of the energy away from the surface, resulting in less heating.

24

LONG TERM
(Thursday through next Sunday)
Issued at 418 PM CST Mon Jan 20 2025

Cold temperatures will prevail through the start of the long term, especially as snow is expected to linger on the ground through Friday. The last night of freezing temperatures for lows is expected Saturday morning, with temperatures quickly moderating through the weekend as the surface high moves east of the area. By Sunday, high temperatures are expected to be back into the middle to upper 60s with lows that morning in the middle 40s to lower 50s. Rain chances will increase again next weekend as the next disturbance moves into the region.

24

AVIATION
(06Z TAFS)
Issued at 1159 PM CST Mon Jan 20 2025

Moisture coming off of coastal low in the southwest GoM is spreading inland. Widespread instances of snow flurries and light sleeting have been reported across southeast Texas and southwest Louisiana. Ceilings are generally hovering above 5000 ft, however with moisture working down through dry layer at the surface, ceilings are dropping into the upper fringe of MVFR. Further increases in winter precipitation are expected, however generally light to moderate VIS due to blowing snow is anticipated and only for southern terminals.
Precipitation will end from west to east Tuesday afternoon with high pressure swiftly building in from the west. Conditions will rapidly improve after 18Z for western terminals and 20 to 22Z for eastern terminals.

Strong north-northeast gradient winds will prevail through much of the period. Gusts 20 to 25 knots can be expected. Winds will diminish but remain from the north after the low has departed and once high pressure has set in.

11/Calhoun

PRELIMINARY POINT TEMPS/POPS
AEX 23 35 13 40 / 40 70 0 0 LCH 25 33 13 35 / 60 90 0 0 LFT 26 33 14 37 / 50 100 0 0 BPT 26 37 17 42 / 70 90 0 0

LCH WATCHES/WARNINGS/ADVISORIES
LA...Winter Storm Warning until 9 PM CST Tuesday for LAZ027>033-044- 045-055-073-074-141>143-152>154-241>243-252>254.

Extreme Cold Warning from 6 PM Tuesday to 9 AM CST Wednesday for LAZ027>033-044-045-055-073-074-141>143-152>154-241>243- 252>254.

TX...Winter Storm Warning until 9 PM CST Tuesday for TXZ180-201- 259>262-515-516-615-616.

Extreme Cold Warning from 6 PM Tuesday to 9 AM CST Wednesday for TXZ180-201-259>262-515-516-615-616.

GM...Small Craft Advisory until 6 PM CST Tuesday for GMZ430-432-435- 436.

Small Craft Advisory until midnight CST tonight for GMZ450-452- 455-470-472-475.

Gale Warning until midnight CST Tuesday night for GMZ450-452-455- 470-472-475.