Area Forecast Discussion

WHAT HAS CHANGED

* Decreased chances for showers and storms today, with mainly dry conditions expected.

KEY MESSAGES

As of 245 PM Saturday...

1) An isolated shower or storm can't be ruled out in the south this afternoon, but much of the area should stay dry.

2) Scattered to numerous showers are expected Monday and Tuesday. Strong to severe thunderstorms are possible Monday, along with locally excessive rainfall both days.

3) Cold-air damming is likely to result in well below normal temperatures through the second half of the week, bringing much more fall-like weather.

DISCUSSION

As of 245 PM Saturday...

KEY MESSAGE 1... An isolated shower or storm can't be ruled out in the south this afternoon, but much of the area should stay dry.

Weak high pressure is currently building into the area from the NE, as a backdoor cold front sinks into central SC. This front is farther south than anticipated, which is keeping any deep convection well to our south as well. Even the sea breeze convection is staying pinned to far SE NC. CAMS have trended drier for today as well. So while a stray shower or storm can't be ruled out this afternoon over our southern zones where 1000-2000 J/kg of MLCAPE is currently in place according to SPC mesoanalysis, no severe weather is anticipated, and much of the area will stay dry. Thus lowered POPs to mainly slight chance, ending by 00z. Otherwise, enough low-level moisture should still be in place for some patchy fog and low stratus early Sunday morning.

KEY MESSAGE 2... Scattered to numerous showers are expected Monday and Tuesday. Strong to severe thunderstorms are possible Monday, along with locally excessive rainfall both days.

A cold front will parallel the Virginia/North Carolina border Monday morning and will slowly sink south into North Carolina on Monday. Depending on how long it takes for the front to sink south, the western half of North Carolina could remain on the warm side of the front long enough to realize some instability and have some strong to severe thunderstorms develop. However, the greater threat is likely to come from strong rainfall considering storm motion is expected to be slow along the front. The Weather Prediction Center continues to have all of central NC in a Marginal Risk (level 1 of 4) for excessive rainfall both days. Monday appears to be the last hot day for some time across the area - while highs will range from the mid 80s to the low 90s on Monday, highs will range from the mid 70s to the mid 80s on Tuesday.

KEY MESSAGE 3... Cold-air damming is likely to result in well below normal temperatures through the second half of the week, bringing much more fall-like weather.

High pressure over Canada will drift east, currently in Manitoba, but eventually sliding to Quebec by Wednesday and then remaining stationary through the rest of the week. The models still have not come into much agreement as to whether a surface low will develop along the Atlantic coastline and move north towards New England, but either way, a ridge of high pressure should extend south from Canada as far south as Georgia at least on Wednesday and Thursday, if not longer. This should keep the weather cool. The current forecast high for Greensboro on Wednesday is 69 degrees, and the last time Greensboro had a high temperature below 70 degrees was May 23. A few locations could even drop into the upper 40s by Saturday morning. All locations will have a chance for scattered showers or drizzle on Wednesday and Thursday, with Friday and Saturday looking drier.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

As of 225 PM Saturday...

Ceilings have scattered and lifted to VFR across central NC early this afternoon. The backdoor cold front has settled well to our south over SC, with NE flow advecting in drier air behind it. Thus while a stray shower or storm can't be ruled out across the south with weak instability in place and the sea breeze, the vast majority of locations will stay dry. Areas of low stratus and fog with associated MVFR/IFR conditions are once again expected to develop late tonight and early Sunday morning. Can't rule out isolated LIFR as well. The threat may be more low stratus over the NW Piedmont (including INT and GSO) and fog over the Sandhills and Coastal Plain (including RWI and FAY), with a relative minimum in either threat in between (including RDU). VFR should prevail everywhere by late morning. Winds initially out of the NE will turn more southerly tomorrow, remaining light (around 7 kts or less).

Outlook: An upper disturbance may bring some showers and storms to mainly the NW Piedmont on Sunday afternoon and evening. A cold front approaching Monday will bring a better chance of showers and storms to the entire area. Unsettled weather may persist under a CAD-regime developing Tuesday-Wednesday, where periods of sub-VFR stratus and fog may exist into late week.

RAH WATCHES / WARNINGS / ADVISORIES

None.