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FXUS64 KEWX 081807 AFDEWX

Area Forecast Discussion National Weather Service Austin/San Antonio TX 1207 PM CST Fri Dec 8 2023

New AVIATION

SHORT TERM
(Today through Saturday)
Issued at 241 AM CST Fri Dec 8 2023

Synopsis/Mesoanalysis: 2 AM surface observations show predominantly southerly winds at our observation stations, with temperatures in the 60s and dew points ranging from the upper 50s into the lower half of the 60s. Tied to an occluded surface low along the North Dakota-Minnesota border, a cold front is apparent far to the north of the region, extending from near Wichita, KS southwest into the OK and TX Panhandles. While the dew point gradient isn't particularly compact across it, a leading dryline has been analyzed south and east of the cold front along an Altus, OK - Midland/Odessa - Fort Stockton axis. The aforementioned boundaries will continue to define the regional surface pattern through this afternoon, with forward progress of the cold front being slow. The front will begin to move southeast toward the area with greater haste overnight tonight as positively-tilted, mid-level troughing materializes from the Southern Plains into the western Great Lakes. The boundary is expected to cross the area from northwest to southeast Saturday morning and afternoon, and should be completely out of the region by the conclusion of the period. Apart from an isolated shower or thunderstorm along/east of US-77 on Saturday afternoon, a dry frontal passage is anticipated over South-Central Texas. Gusty northwest winds will become established behind the departing front on Saturday afternoon, particularly over the southern Edwards Plateau and Rio Grande Plains. Working in tandem with very dry air advecting in from the northwest, said winds could support periods of elevated to near-critical fire weather conditions over the Rio Grande Plains and southern Edwards Plateau on Saturday afternoon.

Predawn: Anticipate temperatures to bottom out in the 50s west of I- 35, with low 60s likely further east. Areas of fog are likely to develop closer to sunrise, with SREF probabilities favoring the southern Edwards Plateau and Rio Grande Plains for the lowest visibilities in our area. Readings below a mile are possible in these locations, with some potential for localized pockets of quarter mile visibilities/dense fog. Will be monitoring visibility trends through sunrise given this potential. Be sure to slow down, use low beam headlights, and allow for extra following distance during the morning commute in these locations.

Today: Well-above normal high temperatures remain forecast across South-Central Texas. The overnight update shows widespread readings in the 70s across the region, with lower 80s possible in portions of the Coastal Plains and Winter Garden. Have maintained an entirely dry forecast, though it's worth noting that probability-matched-mean (PMM) QPF progs from the 00Z Friday HRRR indicate some very light rainfall potential over primarily Lavaca County between 6 AM and Noon. Have inserted some silent 10% precip probs over this portion of the area given this signal, though very low confidence precluded any explicit mentions of precip in the overnight update. Expect a rain-free forecast to prevail through the morning hours, but will nevertheless monitor trends.

Tonight: Another round of fog development is anticipated during the predawn hours, with readings at/below a mile possible in the Coastal Plains and southern Edwards Plateau. Be sure to budget extra time if traveling in these areas during this portion of the period.

Saturday: The cold front discussed in the synopsis remains on track to pass through the area during the morning and afternoon hours. A dry frontal passage is expected across the vast majority of the region, though an isolated shower or thunderstorm can't be ruled out during the afternoon hours along & east of US-77. Elevated to near- critical fire weather conditions are possible over the Rio Grande Plains and southern Edwards Plateau as gusty northwest winds become established behind the front. Please refer to the Fire Weather section below for additional information.

LONG TERM
(Saturday night through Thursday)
Issued at 241 AM CST Fri Dec 8 2023

Saturday night, a sharp trough axis will be digging through Texas.
As the long term period begins 00Z Sunday, the surface cold front will be just exiting our Coastal Plains counties, with any lingering isolated showers over our far SE areas ending before 9pm. Northerly winds will begin to whip up, with 15-25 mph sustained winds overnight gusting at times to 30-40 mph. We still do not anticipate the need for a Wind Advisory at this time, but folks may want to make sure their lightweight holiday decorations are secured. Near critical fire weather conditions will be in place near the Rio Grande during the evening, but RH will increase above 35 percent areawide before midnight.

Morning lows will be in the mid 30s to mid 40s for most locations.
Wind speeds are forecast to gradually diminish during the day on Sunday as surface high pressure builds in, and under ample sunshine highs will reach the mid 50s to lower 60s. But dew points will continue to fall through the afternoon into the teens, and PWATS will likely be in the neighborhood of 0.15" overnight, near record lows per DRT sounding climo. Combined with light winds, this will promote strong radiational cooling and a freeze is likely for many areas. NBM probabilities for a freeze have increased since this time yesterday and the deterministic NBM is finally on board as well, though I lowered MinT slightly still. While forecast lows are currently 28-36, it's possible these get lowered a couple more degrees in future forecasts. Freeze Warnings will probably be needed for portions of the region.

Southerly return flow will quickly redevelop on Monday and especially Monday night. Gradual moisture return is forecast through the middle of next week. Our next trough is progged to cut off near the Four Corners Wednesday, with POPs locally increasing for Wednesday through Thursday night. The best chances for appreciable rains will likely be in central and western areas, but should spread east next Friday into Saturday as the system opens and becomes more progressive. The most likely arrival date for the next cold front will be next Saturday.

AVIATION
(18Z TAFS)
Issued at 1158 AM CST Fri Dec 8 2023

MVFR to IFR ceilings and fog at KDRT erodes within the next hour or two. Few clouds to sky clear conditions will prevail for majority of the afternoon and the first half of tonight. Conditions deteriorate at the I-35 TAF sites (KAUS, KSAT, KSSF) overnight into Saturday morning with IFR to LIFR ceilings and reduced visibility. For KSAT and KSSF, brief VLIFR conditions may develop. KDRT could see enough low clouds for brief flight category reductions but the confidence remains too low to include in this TAF package at this time. Overall expect for the flight categories to improve by the late morning and early afternoon as a cold front advances southward through the region. Breezy north-northwesterly winds develop following passage of the front, especially later into the afternoon and into Saturday evening.

FIRE WEATHER
Issued at 241 AM CST Fri Dec 8 2023

Periods of elevated to near-critical fire weather conditions are possible over the southern Edwards Plateau and Rio Grande Plains on Saturday afternoon as gusty northwest winds combine with very dry air filtering in behind a departed cold front. Near-critical fire weather conditions will be most likely along the Rio Grande and in Edwards County, where minimum relative humidities in the mid-upper teens will overlap with sustained 15-20 MPH winds. A Rangeland Fire Danger Statement may be needed over this portion of South-Central Texas on Saturday afternoon. Brief periods of localized critical fire weather conditions can't be ruled out in Edwards, Kinney, and Val Verde Counties, though above normal fuel moisture will likely preclude the need for any Red Flag Warnings. Avoid any activities that could inadvertently lead to the ignition of a wildfire in the southern Edwards Plateau and Rio Grande Plains on Saturday afternoon.

PRELIMINARY POINT TEMPS/POPS
Austin Camp Mabry 60 74 40 58 / 0 0 0 0 Austin Bergstrom Intl Airport 60 75 41 59 / 0 0 0 0 New Braunfels Muni Airport 60 76 41 61 / 0 0 0 0 Burnet Muni Airport 54 69 35 56 / 0 0 0 0 Del Rio Intl Airport 54 76 41 62 / 0 0 0 0 Georgetown Muni Airport 58 72 38 58 / 0 0 0 0 Hondo Muni Airport 55 78 39 61 / 0 0 0 0 San Marcos Muni Airport 59 75 39 59 / 0 0 0 0 La Grange - Fayette Regional 65 76 42 57 / 0 10 10 0 San Antonio Intl Airport 59 76 42 60 / 0 0 0 0 Stinson Muni Airport 60 77 44 62 / 0 0 0 0

EWX WATCHES/WARNINGS/ADVISORIES
None.

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