textproduct: Columbia

WHAT HAS CHANGED

A Tornado Watch has been issued until 1p across the entire forecast area. Aviation discussion updated for 12z TAFs.

KEY MESSAGES

- 1. A cold front is forecast to bring a line of strong to severe storms this morning, with strong and gusty winds expected in advance of the front and just behind it. - 2. Another strong cold front is forecast to push into and through the area Sunday and Monday. - 3. Well below normal temps expected early next week, with a widespread frost possible.

DISCUSSION

KEY MESSAGE #1: A cold front is forecast to bring a line of strong to severe storms this morning, with strong and gusty winds expected in advance of the front and just behind it.

Water vapor imagery tonight reveals a sharp mid-level shortwave over eastern TX and Louisiana, rapidly propagating northeastward. A broad area of low pressure exists ahead of this system, with a large and deep low pressure centered across the northeastern US and extending along the eastern slopes of the Appalachians. A secondary surface low is developing in the immediate vicinity of the aformentioned shortwave, helping to drive the development of a QLCS. This is a pretty robust QLCS at this hour, supported by strong synoptic support and 50-100 j/kg of 3k CAPE. The overall setup favors this to continue marching eastward towards our forecast area. RAP/HRRR/REFS guidance all forecasts generally 250-500 j/kg of SBCAPE & 50-100 j/kg of 3km CAPE. Strong warm advection is fostering surface dewpoints in the low to mid 60s which should be sufficient to actually yield CAPE similar to what the guidance is showing. As the shortwave continues to merge with the deep trough to its north, low-level flow will continue to strengthen ahead of the line of storms, with 0-3km shear on the order of 40-50 knots as the line approaches. This forecast remains on track, with the QLCS pushing into our forecast area shortly. A Tornado Watch has been hoisted for the entire area until 1p in anticipation of potential damaging wind gusts and brief, spin up tornadoes. Please have weather awareness today!

The expectation is that this line will maintain and approach the region between 7a and 12p, pushing eastward by the end of that timeframe. This line has been a pretty frequent producer of mesovortices as it has propagated across Louisiana and Mississippi last night and early this morning. With the aformentioned low-level CAPE profile, in addition to strong, southwesterly 0-3km shear vectors, expect that the line will be capable of strong to severe weather. Strong to damaging wind gusts are the primary threat (and this is outside of 30+ mph non thunderstorm gusts ahead of the front), with some weak spin up tornadoes possible given the somewhat favorable setup for mesovortex production.

Once the line pushes through, the airmass should begin drying as winds shift out of the west and northwest at the surface. The gustiness will likely remain but fall back into the 20-30 mph range instead of 30+ mph near the front. Highs are probably being hit as this AFD is written give that we are still in the 70s and temps are expected to fall behind the front.

KEY MESSAGE #2: Another strong cold front is forecast to push into and through the area Sunday and Monday.

After a couple of days with near normal temps and dry conditions, a broad warm sector is forecast to overspread the region ahead of a deep, large surface low pushing into the Great Lakes region. A weak shortwave is forecast to precede this deep trough, yielding strong moisture return on Sunday. Isentropic lift is expected to lead to some showers during the day on Sunday as moisture rapidly increases across the area. This moisture plume should push to the north of the area thereafter, with an intense cold front pushing eastward on Monday morning. Depending on the timing of this front, another round of strong storms is possible on Monday morning or early afternoon. Regardless, more rain/storms may approach Monday with strong, non-thunderstorms wind gusts likely as well with this system.

KEY MESSAGE #3: Well below normal temps expected early next week, with a widespread frost possible.

Behind the aformentioned front, a strong, arctic high pressure is forecast to shift into the central Plains and OH Valley. LREF guidance seems to be in fairly good agreement that this airmass next week will be cold & dry. The grand ensemble mean shows surface high pressure in the 85-95th percentile pressures across the deep south as the surface high settles into the area. Temperatures are forecast to end up in the low 30s both Monday and Tuesday night. Given that things are beginning to green up & bloom, we are growing concerned about a potential widespread frost early next week. Stay tuned to the forecast if you have any plants outdoors that may need protection from the cold!

AVIATION /12Z THURSDAY THROUGH MONDAY/

Restrictions Likely Develop this Morning....

A line of showers and thunderstorms will move through the forecast area this morning. Ceilings are expected to fall into MVFR ahead of the line, with further reductions possible this morning as the convection moves over the terminals. Strong wind gusts are possible with any thunderstorms that pass over a terminal. Gusty winds are expected to develop outside of thunderstorms today, both ahead of and behind the frontal boundary. VFR conditions return between 21Z and 23Z as drier air works into the area behind the cold front with winds gradually diminishing tonight.

EXTENDED AVIATION OUTLOOK...No notable restrictions expected until early next week.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Lake Wind Advisory until 8 PM EDT this evening for SCZ016-018- 020>022-025>031-035-037-038-041-115-116-135>137. GA...Lake Wind Advisory until 8 PM EDT this evening for GAZ040- 063>065-077.