textproduct: Columbia

WHAT HAS CHANGED

Added mention of possible isolated stronger storms on Tuesday to Key Message #1. Aviation discussion updated for 18z TAFs.

KEY MESSAGES

- 1. Chances for showers and storms continue each day this week as temperatures hover around average. A couple strong to marginally severe storms possible Tuesday.

DISCUSSION

- 1. Chances for showers and storms continue each day this week as temperatures hover around average. A couple strong to marginally severe storms possible Tuesday.

The upper trough is clearly visible in WV imagery as it becomes increasingly closed off from the synoptic flow. The dry slot of this developing mid level low is seen over the Upstate and into the northern Midlands. This has led to a tight PWAT gradient across the FA with GOES derived PWAT's near 2.20" in the southeastern Midlands, decreasing to 1.60-1.80" toward the northern Midlands. A diffuse but weak front has also become nearly stalled in the Upstate. Forcing from the trough is bringing scattered convection across southern GA, which is gradually expanding into the southern CSRA and southeastern Midlands. Scattered showers/storms are expected the remainder of the afternoon and into this evening where the main risk is locally heavy rainfall and possibly isolated instances of flash flooding if training occurs.

The mid level low is progged to meander through northern GA toward the southern part of the Blue Ridge Mountains the next couple of day's with wrap around moisture working back into the FA, though some mid level dry air is expected to remain in place, especially Tuesday. Cooling mid level temperatures/steepening mid level lapse rates Tuesday should bring solid CAPE profiles with near 2000-2500 J/kg of SBCAPE developing as effective shear nears 20-30 kts. Generous BL mixing is also expected to yield DCAPE around 800-1200 J/kg. Overall, forcing from the low in this environment is expected to bring more scattered convection during the afternoon and into the evening Tuesday where an isolated strong to marginally severe storm could be possible, bringing the risk of damaging downburst wind gusts. Wednesday is expected to be set up fairly similar as the low remains in the region, but the risk for stronger storms seems a bit lower. Ensemble guidance is in fairly good agreement that the mid level low will slowly be picked up in the synoptic flow as a robust ridge near the NAEFS climatological max builds off the East Coast. The ridge should allow deep southerly to southwesterly flow to persist late in the week and into this weekend, keeping PWAT's during this period near 2" with seasonable temperatures and diurnally driven chances for showers/storms each day.

AVIATION /18Z MONDAY THROUGH SATURDAY/

VFR conditions prevail into this evening outside of any convectively driven restrictions. Some stratus and fog is possible early Tuesday morning which may lead to MVFR/IFR conditions through sunrise.

The deepest moisture has shifted east toward the coast early this afternoon with CIGS returning to VFR almost everywhere. Light southerly wind should increase to around 6 to 8 knots this afternoon. Another round of showers and storms expected today but coverage looks to be a bit less and may favor the eastern Midlands. Brief restrictions remain possible in the stronger storms along with a few elevated wind gusts of 20-25 kts. Environment seems favorable for some sort of restrictions again tonight, particularly given light winds in the boundary layer, but guidance is inconsistent with where fog/stratus may develop. For now have included TEMPO groups for restrictions in the latter half of the TAF period at the more prone sites of AGS/DNL/AIK that will need additional refinement with subsequent forecast packages. For Tuesday, VFR conditions should return by late morning/midday as scattered showers and storms fire up again in the afternoon.

EXTENDED AVIATION OUTLOOK...Periodic showers-storms expected in the afternoons this week along with CIG/VSBY restrictions in the mornings.

CAE WATCHES/WARNINGS/ADVISORIES

SC...None. GA...None.