The strongest "sharp change" cold front of this winter - and the strongest in early March since 2014 - ripped through all of the southern tip of Texas overnight. The initial surge beat our expectations by about 3 hours, with temperatures in the 50s to around 60 at sunset Sunday night - but the real push of polar air arrived after midnight, and by the school bus ride, most areas were in the upper 30s to lower 40s with "feels like" temperatures near 30 for many. As shown in the attached graphics, the difference in "feels like" temperatures for the mid Valley between 1 PM March 3 and 9 AM March 4 was up to 60 degrees. The polar airmass settles in for the next 24 to 36 hours, with current temperatures (37 to 41) likely holding through 9 AM Tuesday, and "feels like" temperatures in the 27 to 32 range. Colder values (33 to 38 air, 24 to 30 "feels like") are likely along SR 285 and SR 16 between Zapata, Hebbronville, and Falfurrias.
Temperatures will remain cold - still 30 degrees below average for many (average is in the upper 70s on March 6) Tuesday afternoon, with a slow moderation back into the 50s Wednesday before southerly winds return and rapidly erase the cold and bring above normal temperatures region-wide for next weekend.
What to Watch For
Temperatures holding between 37 and 42 Valley, 33 to 38 ranchlands, on Monday.
"Feels like" temperatures 27 to 32 Valley, 25 to 30 ranchlands, on Monday.
Wind chill advisory, issued for several hours of "feels like" temperatures between 21 and 30, is in effect for the Valley counties, through 9 AM Tuesday
Feels like temperatures in the lower-mid Valley Tuesday afternoon will only rise into the 30s (actual temperatures into the 40s). Slightly higher across the Rio Grande Plains/Brush Country where some sunshine will help push closer to 50 or above.
Freeze/Near Freeze Potential
Dry air filtering across the ranchlands, perhaps into northern Hidalgo, northern Starr, and the King Ranch, may allow a few hours of 30 to 32 degree temperatures between 3 AM and 8 AM Tuesday. Confidence is medium but increasing, and our future forecast may be adjusted to match by mid afternoon. Freeze warnings may be required.
Across the mid Valley, and perhaps parts of the lower Valley, we'll need to watch how much low level dry air arrives this afternoon and evening. There is the potential for late night/early morning temperatures to dip into the lower or mid 30s, but when combined with low "dewpoint" temperatures (i.e. low to mid 20s), tender vegetation can be prone to damage.
Rough seas and strong north winds gusting up to 30 knots will continue through Tuesday, with seas (combination of wind waves and swell) persisting at 8 to 11 feet, locally higher.
Patchy light rain/drizzle will reduce visibility to 1 nautical mile or less, but fog is not expected early this week.
The combination of strong north winds, cold temperatures, and light rain/drizzle is conducive to pelicans trying to find safe spots along Bahia Grande. The Gaiman Bridge is susceptible to pelican "trapping" in wind eddies through Tuesday morning.
Potential Impacts/Suggested Actions
Shelters should to be opened for homeless/others through at least midday Tuesday.
Space heaters should be operated safely and have an automatic shut-off switch if tipped over or operating poorly
Several layers of clothes are better than a single jacket.
Due to early and "full" green-up and flower bloom-out, the potential for cold weather damage is much higher to sensitive tropical blooms this year, at this time, than would be the case if this cold snap occurred in December-mid February.
Protect plants by covering or moving indoors immediately. Best potential for impact is from Harlingen to Weslaco to north McAllen/Edinburg (where green-up occurred first and most "full"). Residents farther west and north who have tender blooms should protect as well from a possible full freeze.
Small craft operators and others should postpone trips through Tuesday. Wednesday will remain difficult to dangerous on the Gulf with improvement on Laguna Madre (though still cloudy and damp).
Difficult, but less hazardous, seas will continue most of the week beyond Wednesday morning.
Drivers along SR 48 (Padre Island Highway) should continue to slow down around the Gaiman Bridge through Tuesday morning.
Fog is likely to become an issue by late Wednesday night as warm air just above the surface overwhelms to last of the cool air at the surface. Cloud decks will lower to the ground in some areas, and visibility could be less than 1/4 mile in spots for the Thursday morning commute. Sea fog may hang tough into Thursday or perhaps Friday before winds should increase enough to dissipate it.