textproduct: Columbia

WHAT HAS CHANGED

High confidence in beneficial rainfall Friday night through Saturday. Significant warmup expected next week. Aviation updated for 18z TAFs.

KEY MESSAGES

- 1. Significant and beneficial rainfall expected Friday night through Saturday.

- 2. Cooler than normal temperatures this weekend followed by a significant warmup next week.

DISCUSSION

Key Message 1: Significant and beneficial rainfall expected Friday night through Saturday.

The weather pattern continues to favor the potential for the most significant rainfall event in over a month Friday night into Saturday. Northern stream energy digging into the Midwest Friday is forecast to phase with southern stream energy moving across the Southern Plains into the Gulf Coast states by Friday evening. NAEFS IVT reaches the 97th percentile with strong moisture advection into the region Friday night through Saturday. Ensemble forecasts of PWATs show a strong gradient across the region with values ranging from 1.7 inches in the southeast Midlands to 1.2 inches in the northern Midlands at 12z Saturday, which likely would favor higher precipitation amounts in the southeast Midlands with a gradient to lower values north. This looks to be a strong overrunning event with a surface low developing along the Gulf Coast and moving off the Carolinas coast with little to no instability available. The eventual rainfall totals and axis of highest precipitation will ultimately be dictated by when the phasing occurs and and if there is any amplification of the trough. However, overall rainfall trends have continued to improve with LREF probability of 1 inch of rain increasing over the past 3 model runs, especially across the southeast Midlands and lower CSRA. NBM also continues to increase in rainfall totals with the 50th percentile values now well over an inch across the entire area. However, the NBM continues to show a large range in values with the 25th percentile ranging from around 0.4 inches north to 1.25 inches south and the 75th percentile ranging from around 1.5 inches north to 2.4 inches south. Regardless, this should be the ideal way to help improve drought conditions with a long duration soaking stratiform rainfall event rather than strong thunderstorms with lots of runoff from dry hard surface conditions.

Key Message 2: Cooler than normal temperatures this weekend followed by a significant warmup next week.

Temperatures this weekend expected to be well below normal with extensive rainfall on Saturday and continued below normal on Sunday behind a cold front as high pressure builds over the region. Temperatures may be nearly 20 degrees below normal for highs on Saturday with highs in the lower 60s as NAEFS 1000mb and 850mb temperatures are at or below the 10th percentile. Temperatures will gradually warm early next week as surface high pressure shifts offshore and a return southerly flow develops. Highs expected to rise back into the 80s by Tuesday and mid to upper 80s by Wednesday ahead of the next approaching system.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Mix of MVFR and VFR cigs early this afternoon. VFR likely into early Friday before MVFR stratus possible.

Any lingering showers have pushes east of the terminals as of 18z but a few isolated showers-storms remain possible later this evening mainly between 23-03z. Coverage is expected to be too low for a TAF mention for any sites currently. Some lingering MVFR cigs will remain through mid-afternoon before all sites should lift to VFR after 20z. Morning stratus looks possible on Friday, but guidance is generally mixed on the extent and timing. For now thinking a MVFR type event is most likely with typical timing starting after 10z. Generally north- northeast winds expected through the period with some gusts up to around 12-15 knots Friday morning.

EXTENDED AVIATION OUTLOOK...Periods of restrictions likely starting Friday night into Saturday as widespread rain overspreads the region. Drier conditions then are expected Sunday and into the early week.

CAE WATCHES/WARNINGS/ADVISORIES

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