... Dry high pressure builds in through Thursday, resulting in a slow cooling trend. Meanwhile, Hurricane Ian will move north into the eastern Gulf of Mexico and approach our area late in the week, affecting our weather by this weekend.
NEAR TERM /THROUGH WEDNESDAY/... As of 230 PM: Sfc high pressure will gradually sink southward out of Canada into the north-central CONUS through the near term forecast period. The southeastern periphery of the ridge will extend into the western Carolinas during this timeframe leading to continued dry conditions and below climo temps. Skies will remain clear through early this evening before upper-level cirrus increases from SE to NW late this evening into Wednesday. High temps will be around 1-3 degrees below climo east of the mtns and 4-7 degrees below climo across the mtns this afternoon thanks to NW'ly flow. Highs will reach the mid to upper 70s east of the mtns with upper 50s to upper 60s across the mtns. Low-end wind gusts will continue across the mtns this afternoon and early evening.
Lows tonight will be ~5-9 degrees below climo despite increasing upper clouds. Lows should drop into the upper 30s to lower 40s across the mtns with mid 40s to lower 50s elsewhere. Mountain valley fog may be limited somewhat by increasing upper-level cirrus and winds remaining at light speeds overnight into daybreak Wednesday. High temps on Wednesday will be even cooler as flow turns more N'ly and NE'ly with temps around 5-9 degrees below climo. Highs will only reach into the upper 60s to lower 70s east of the mtns with lower 50s to mid 60s across the mtns. Low-end wind gusts will be possible once again across the mountains on Wednesday.
SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... As of 210 pm Tuesday: Anomalous upper trough is forecast to move quickly off the East Coast early in the short term...too fast (unfortunately for us) to "grab" T.C. Ian and send it into the western Atlantic. Ian is therefore expected to find itself within a nebulous flow pattern...wobbling slowly north across the Florida peninsula at the start of the period. That being the case, confidence in the track of the remnant circulation is below average beyond Day 3 or 4. (This is born out in the latest ensemble track guidance...a veritable mess beyond that time frame.) Having said that, impacts from Ian (mainly in the form of rain) are still likely across our forecast area by the end of the short term, but the magnitude of those impacts remains very uncertain... due to a variety of unknowables at this point.
In the interim, gusty winds are forecast to become established across the area on Thursday...continuing through the end of the period as the gradient tightens between Ian, a 1030+ mb surface high settling into the northeast, and resultant inverted ridge sharpening down the Eastern Seaboard. Gusts in the 25 to 35 mph range appear likely, especially during each afternoon. While the guidance consensus is to slow down the surge of tropical moisture and precip development across our CWA, likely PoPs nevertheless appear warranted across the southeast fringe by early Fri evening. Lingering anomalously low heights and NE low level flow followed by increasing/thickening cloud cover is expected to yield well-below normal max temps and slightly below normal mins through the period.
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... As of 220 pm Tuesday: Conditions are expected to be in a gradual state of deterioration across the forecast area at the start of the extended, with precip chances ramping up toward categorical by daybreak Saturday...as tropical moisture will likely be surging from the southeast. Having said that, T.C. Ian is expected to be encountering its next difficulty early in the period, as it will encounter the leading edge of sprawling and fairly strong high pressure covering much of the Southeast and Mid-Atlantic. The interaction of these features creates the most uncertainty regarding the track of the cyclone's remnants over the weekend into early next week. Interestingly (considering the ridiculous degree of spread in ensemble guidance), a consensus appears to be emerging among the global deterministic models to drag the weakening and increasingly less-tropical remnants into north Georgia by the end of Saturday, with some hint that a dry slot will surge into the forecast area for late Sat/Sat night. And in fact, while the remnants remain over the region for a while before dissipating...or perhaps kicking out to the east, these solution don't produce much in the way of heavy rainfall past Saturday evening.
Thus, Fri night/Saturday are currently looking like the rainiest period. A number of factors are creating a considerable amount of uncertainty regarding QPF. First: with the aforementioned surface ridge in place...cold air damming will quickly become locked in once precipitation develops...with the resultant stable air mass cutting into the rainfall rate potential. Second: with tropical rain bands/ deep convection expected to focus along the upstream coastal front, some degree of moisture transport interruption into the area is a good bet, which would result in further hindrance to rainfall rate potential. Combine that with the lingering intensity and track uncertainties, and QPF is a big ?. Based upon the current emerging consensus in the guidance, confidence is increasing that much of the area will see at least a couple of inches of rain in the Fri night/ Saturday time frame, but how much above/beyond that remains a mystery for now.
Conditions should steadily dry out through the remainder of the period, but some degree of moisture (and PoP) lingers into early next week. Temps should remain below normal throughout.