Marine Weather and Tide Forecast for Knoxville, TN

SHORT TERM
(This evening through Saturday)
Issued at 308 PM EDT Fri May 16 2025

Key Messages:

2. Severe thunderstorms possible with threats of damaging winds, large hail, and a lower but still significant threat of tornados this afternoon into tonight.

2. Drier conditions for Saturday.

Discussion:

The atmosphere is primed for severe storms out ahead of the approaching short wave trough, as HRRR/RAP forecast continue to show MLCAPE this afternoon between 2000 and 2500 J/Kg with EBShear of around 50 to 60+ kts. A remnant outflow boundary near the northern Plateau into Southwest VA has the potential to be the focus for storms this afternoon out ahead of tonight's main event, and supercell structures would be likely along with the potential for hail, damaging winds, and an increased threat of a tornado near the boundary. This threat will be conditional on if the cap erodes enough for these additional storms to get going which is still uncertain, and the hi-res CAMS have had a poor handle on this daytime convection overall and unfortunately have added little to the confidence in this scenario so far.

Despite the loss of heating after sunset, the instability will remain significant tonight out ahead of the main round of convection as lapse rates steepen with the shortwave trough moving in. The HRRR/RAP forecasts show MLCAPES still around 2000 to 2500 J/Kg as the convection approaches. The LLJ will also increase as the line approaches with 850 mb winds increasing to near 50 kts, and EBShear OF 60+ kts is indicated along with increasing low level shear (with 0-1km shear reaching 35+ kts). Hi-res CAMS and other models have been more consistent in showing a line of convection moving through overnight, with timing still looking most likely to fall between 03z and 09z. All severe hazards look possible, with damaging winds and large hail the primary threats along with a lower, but still significant (around 5 percent within 25 miles of a point), threat of tornadoes. In addition, forecast PW values of 1.6 to 1.8 will be near the climo max, and NAEFS IVT values are forecast to be near climo max as well. This is a strong signal for very heavy rain rates, which may result localized flooding especially in areas that see repeated rounds of rainfall. The highest risk for flooding would likely be across the north given the increased potential for storms there this afternoon.

Saturday will turn drier behind this system, with plenty of sunshine and a warm afternoon.

LONG TERM
(Saturday night through next Friday)
Issued at 308 PM EDT Fri May 16 2025

Key Messages:

1. Warm with a some showers and storms around at times Sunday through Monday.

2. Precipitation chances increase for Tuesday into Wednesday, along with a chance for strong to severe storms.

3. Cooler late next week in the wake of a cold front.

Discussion:

Saturday night looks to be mainly dry, but despite low amplitude upper level ridging slowly building over our area during the Sunday/Monday time frame, weak ripples in the flow are expected to bring showers and thunderstorms to our area at times. By Tuesday, a stronger upper trough will approach the Mississippi Valley with increased chances for showers and thunderstorms Tuesday into Wednesday across portions of the Tennessee Valley and Southern Appalachians, and there is an uptick in the chances for strong to severe storms with this system. Low confidence on how models are handling the latter periods behind the cold front. It may be drier, but some models want to park a closed upper low nearby so at this point the forecast will keep lower chances for showers and storms Thursday and Friday.

AVIATION
(06Z TAFS)
Issued at 126 AM EDT Sat May 17 2025

Conditions will be mainly VFR outside of thunderstorms. The exception is MVFR CIGs in the morning likely at TRI. A line of storms will move through the region overnight. Some storms may be severe with gusty winds being the main threat. Low level wind shear is around 40 knots across the region. The line should move through fairly quickly with clearing expected this morning with winds becoming more westerly.

PRELIMINARY POINT TEMPS/POPS
Chattanooga Airport, TN 87 65 85 66 / 10 10 50 30 Knoxville McGhee Tyson Airport, TN 83 62 82 63 / 10 10 30 30 Oak Ridge, TN 84 62 82 63 / 10 10 30 30 Tri Cities Airport, TN 80 57 78 58 / 20 0 10 10

MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.