textproduct: Raleigh

WHAT HAS CHANGED

* Potential for meaningful measurable rain now focusing on Friday with the potential for a rather unsettled day, especially during the afternoon and evening.

* Raised low temperatures for Thursday night.

KEY MESSAGES

As of 240 PM Tuesday...

1) An increase in deep layer moisture combined with a series of disturbances aloft and eventually a cold front will result in an increasing chance of showers for late Wednesday into Thursday that maximizes on Friday.

2) Well above normal temperatures on Wednesday and especially Thursday with muggy conditions will fall to near levels seasonable by Sunday and Monday.

DISCUSSION

As of 240 PM Tuesday...

KEY MESSAGE 1... An increase in deep layer moisture combined with a series of disturbances aloft and eventually a cold front will result in an increasing chance of showers for late Wednesday into Thursday that maximizes on Friday.

A rather active mid and upper level pattern across the CONUS for the rest of the work week features a weakening short wave trough that lifts across the Deep South into the southern Appalachians on Wednesday night with trailing energy that moves across NC early Thursday. A stronger short wave moves across the OH Valley on Friday and then into the mid-Atlantic on Friday night. While the best forcing for ascent tracks north of the Carolinas, ascent will be sufficient and supplemental by an advancing cold front the briefly stalls across the western Carolinas on Thursday night and is then nudged eastward by the mid/upper trough with the front crossing the Carolinas on Friday afternoon and Friday night. It's worth highlighting that precipitable water values across central NC range between 1.5 and 2.0 inches which is from 225 to 250% of normal! There is the potential that rainfall amounts may be enhanced by convection although limited instability and modest lapse rates will likely preclude the ability of deep convection to utilize the 30-60 kts of deep shear for severe storms.

Despite all of the ingredients for rain, the main players in this event have evolved considerably as the event has drawn closer and the forecast still contains a greater than typical amount of uncertainty. Rainfall totals from Wednesday night through Friday night in the quarter to half inch range appear reasonable. As noted in the previous discussion, the possible ranges of QPF are large. for instance the latest EC ENS ensemble has the 10th percentile ranging from 0.10-0.25" and the 90th ranging from to 1-1.5 inches. There is growing confidence that a very large portion of this rainfall will occur on Friday, especially Friday afternoon across eastern areas.

KEY MESSAGE 2... Well above normal temperatures on Wednesday and especially Thursday with muggy conditions will fall to near levels seasonable by Sunday and Monday.

A warm airmass will spread into central NC this work week with low level thickness values climbing into the 1380s m on Thursday morning. This will support highs in the upper 70s to lower 80s, warmest on Thursday when highs will be 13 to 17 degrees above average. Clouds and a southerly flow on Wednesday and Thursday night will result in a warm and muggy night. A common pattern recognition technique is that the night before a cold frontal passage is often quite warm given the clouds and nocturnal southerly wind. Lows on Friday morning should range in the lower and mid 60s which is 20 to 26 degrees above average!

Temperatures will cool down to near average early next week with highs in the lower to mid 60s for Sunday and Monday.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

As of 120 AM Wednesday...

Patchy fog has begun to develop across parts of central NC, and it is likely to get more widespread overnight before lifting by mid- morning. Some MVFR stratus is also possible this morning, especially in the west, before VFR returns everywhere in the afternoon. Winds will be mostly calm tonight, increasing to 5-10 kts during the day and veering to the S/SE.

Outlook: Increasing moisture combined with a series of upper level disturbances and a cold front will result in in increasing chances of showers and possibly a thunderstorm Wednesday night into Thursday and especially on Friday which may result in adverse aviation conditions. Improving conditions are expected for Saturday and Sunday.

CLIMATE

Record High Temperatures:

November 4: KGSO: 83/1946 KRDU: 84/1946 KFAY: 86/1974

November 5: KGSO: 82/1914 KRDU: 85/2003 KFAY: 86/2003

Record High Minimum Temperatures:

November 5: KGSO: 65/2003 KRDU: 66/1977 KFAY: 67/2003

RAH WATCHES/WARNINGS/ADVISORIES

None.