textproduct: Raleigh

WHAT HAS CHANGED

* A backdoor front will bring low clouds and patchy fog Wednesday morning.

* The chance of rain remains Sunday into Monday, but confidence remains low.

KEY MESSAGES

As of 218 PM Tuesday...

1) Patchy fog and low stratus will build over the region early Wednesday, slowly lifting during the afternoon hours tomorrow.

2) High pressure will keep dry and near to above normal temperatures through Saturday. A chance of rain remains Sunday into Monday.

DISCUSSION

As of 218 PM Tuesday...

KEY MESSAGE 1... Patchy fog and low stratus will build over the region early Wednesday, slowly lifting during the afternoon hours tomorrow.

A backdoor cold front is presently located to our north in the Delmarva area and off the northern Mid-Atlantic coast. This front is forecast to approach overnight tonight and early tomorrow morning. While the actual front is not likely to move through, it will lead to pooling of moisture in the low-levels. The northeast moist low- level flow will lead to increasing surface dewpoints into the 50s along and east of the Triangle by sunrise Wednesday.

Guidance is pretty consistent on a layer of low stratus spreading west from the Coastal Plain into the Piedmont during the overnight and early morning hours. With dewpoints also increasing, patchy fog will also be possible, especially in outlying areas where winds go calm. This layer of low stratus is expected to gradually lift and disperse during the mid to late afternoon Wednesday. Highs tomorrow will be a touch cooler than today as a result of the cloud cover and slightly lower thicknesses, generally upper 60s west to low/mid 70s in the east.

KEY MESSAGE 2... High pressure will keep dry and near to above normal temperatures through Saturday. A chance of rain remains Sunday into Monday.

High pressure ridging will continue to bring seasonal to above average temperatures through Saturday. Our warmest day is expected to be Friday, ahead of another backdoor front that slides through early Saturday. Highs on Friday could be some 10-12 degrees above normal in the upper 70s to around the low 80s.

The backdoor front is forecast in much of the guidance to move through early Saturday, with cool 1030 to 1034-mb high pressure extending down into the region into early next week. This should favor highs generally in the upper 60s to middle 70s.

We continue to monitor the chance of rain late Sunday afternoon into midday Monday, with perhaps another chance by the middle to latter part of next week. But focusing on the Sun-Mon period, there remains still a bit of ensemble spread. Specifically, the machine-learning ensemble guidance continues to be on the dry side, as a result of a more flat and muted mid-level shortwave, thereby limiting isentropic ascent. Some wetter ensemble solutions show a more developed wave tracking through and thus better rain chances. But even given that, the spread in rainfall is still large, ranging from just a trace to three quarters of an inch. Thus, confidence remains low on expected rainfall, if any, at this stage.

AVIATION /18Z TUESDAY THROUGH SATURDAY/

As of 155 PM Tuesday...

TAF period: High confidence that VFR and fair weather will continue across central NC into the early evening hours tonight. After 04Z, an area of IFR to LIFR stratus an some fog will develop across the Coastal Plain of NC and expand and shift west. There is high confidence that stratus with CIGS around and then below 1kft will develop at KRWI between 04Z and 06Z and KFAY between 06Z and O8Z and persist through the daybreak hours with the potential for periods of IFR fog as well. At KRDU, confidence is a little lower but there's a good probability of stratus and some fog developing 06Z and O8Z. Further west, confidence is lower at KGSO and KINT but still sufficient to include prevailing IFR CIGS beginning between 10Z and 13Z. Restrictions should be slow to improve area wide with the stratus gradually lifting and fog burning off during the late morning hours with most locations becoming VFR between 15Z and 18Z.

Light winds are expected through the period with northeast winds at 4 to 8kts this afternoon, very light northeast winds at 5kts or less tonight and northeast winds at 6 to 10kts on Wednesday afternoon.

Outlook: Restrictions should dissipate areawide by mid afternoon Wednesday. Additional rounds of CIG and VSBY restrictions are possible with decreasing confidence and degree on Wednesday night and Thursday night. Otherwise, dry VFR conditions are expected into the weekend.

RAH WATCHES/WARNINGS/ADVISORIES

None.