Houston/Galveston, Texas

New DISCUSSION, AVIATION, MARINE

• Isolated to widely scattered showers today, especially along and east of I-45.
• Dry and warmer conditions expected Sunday into Monday.
• Cold front showers/thunderstorms on Tuesday. A few heavier thunderstorms possible. Autumn-like air behind the front.

Southeast Texas once again finds itself in a soupy atmosphere, with PWATs averaging ~1.70" areawide. Sfc dew points are primarily in the low 70s, with afternoon temperatures likely warming into the low 80s in most spots. It is a tropical airmass for your Halloween this year. Unlike yesterday, we do not have a robust synoptic system to provide large-scale lift. Nor do we have any meaningful shortwaves to provide lift. However, we do have a weak, southward drifting boundary along with diurnal forcings that should suffice for isolated to scattered shower activity. We used an NBM/HRRR/Global Deterministic blend to give us our ~30-40 PoPs (primarily along and east of I-45). PoPs are lower, but not non-existent, farther west, averaging 15-25% along the Brazos River.

The water vapor rich atmosphere will only allow for minimal cooling overnight. Sunset temperatures are expected to average in the mid/upper 70s. By midnight, temperatures are expected to range from the low 70s south of I-10 and w/in the urban heat island, to upper 60s elsewhere. Not a bad temperature range for Halloween festivities. The first two days of November (Sunday / Monday) are looking quite warm and humid, with afternoon temperatures averaging in the mid 80s inland, and around 80 at the coast.

A very active subtropical jet pattern is evident on water vapor imagery. A deep trough extends over the Pacific well west of California and Mexico. A strong, moist, diffluent sub-tropical jet ahead of the trough is pushing deep tropical moisture in the direction of SW CONUS. Meanwhile, a strong mid/upper low is diving southward over the Pacific Northwest. The two features should phase together over western CONUS on Sunday-Monday. The subtropical jet will infuse the system with tropical moisture in the mid/upper levels, while deep LL flow from the Gulf will surge sfc tropical moisture northward over central CONUS. The Texas atmosphere should start to feel the lift from this system as it ejects eastward from the Rockies, with LL lee-side cyclogenesis expected over the plains.

The set up described above is a heavy rain and severe thunderstorm red flag. But if the current guidance has anything to say about it, the overall synoptic dynamics are more likely to favor severe thunderstorms to the north of our region. The Storm Prediction Center (SPC) is showing a Level 2 of 5 risk of severe weather over portions of Kansas, Oklahoma, and north Texas on Monday. But if you peer at the SPC convective outlook map, you`ll notice that a Level 1 of 5 risk is in effect over portions of central and western Texas down to the Mexico border on Monday. This is because the convergence along the trailing cold front coupled with an increasingly sheared environment should suffice for at least some deep convection along the boundary. Thus, we`ll have to monitor this front closely as it pushes into southeast Texas on Tuesday We think we`ll at least see a broken line of showers and thunderstorms push through the area on Tuesday. But we cannot rule out a few stronger thunderstorms capable of damaging wind gusts.

The air mass behind the front looks beautiful, with highs in the 70s and lows mostly in the 50s. Our northern zones and rural cold spots are likely to dip into the 40s. Autumn should make a comeback in the front`s wake.

Self

IFR/MVFR will linger into the early afternoon before becoming mostly VFR through the rest of today. Isolated to widely scattered SHRA is likely near the coast and east of I-45. Confidence in SHRA is too low to mention in many of the TAFs. But keep in mind that we do expect some shower activity today. Couldn`t rule out an iso TSRA near the coast, where shallow convection has developed in the vicinity of Galveston Bay during the late morning hours. Winds should remain light, and become more NE or N at times.

There is increasing concern for IFR/LIFR cigs and vis overnight, especially after 05-07 UTC, at all terminals. The best chance of LIFR appears to be during the 08-13 UTC time frame. These low cigs/vis could remain resilient well into the morning and possibly into midday tomorrow.

Self

Generally light easterly flow is expected through the weekend. A few isolated showers and thunderstorms are expected today. By Monday, winds veer southeasterly and start to increase, with moderately southerly winds ahead of an approaching cold front on Tuesday. The front pushes offshore by Tuesday afternoon or evening. Showers and thunderstorms are expected along and just ahead of the front. A locally stronger thunderstorm capable of 40+ knot gusts are possible. Gusty northwest winds are likely behind the front late Tuesday into Wednesday. Our current forecast shows 15-25 knot NW winds and 3-5 foot Gulf seas. However, winds and seas can sometimes over perform, especially when ocean temperatures remain on the warm side (mid/upper 70s). So we cannot rule out having to revise winds and seas upwards, especially if temperatures behind the front are looking a little colder.

College Station (CLL)  65  84  66  85 /  10   0   0   0
Houston (IAH)  68  83  69  83 /  10  10   0   0
Galveston (GLS)  71  79  72  81 /  10  10   0  10

TX

None.

GM

None.