textproduct: Raleigh

WHAT HAS CHANGED

As of 235 PM Thursday...

* Slight upward adjustment to high temperatures on Fri and downward adjustment to minimum temperatures Sun morning.

* Winds and wind gusts were increased on Fri, especially behind the frontal passage.

KEY MESSAGES

As of 235 PM Thursday...

1) A strong cold front will bring light to moderate rain, seasonably gusty winds, and a sharp drop in temperatures Friday into Saturday.

2) Adverse fire weather conditions possible Friday and again on Saturday.

3) Widespread frost conditions likely with localized freeze possible Sun morning.

4) Dry weather is expected to return for the weekend through at least mid week resulting in a prolonged period of below average precipitation exasperating drought conditions and sustaining or prolonging the abundance of pollen in the air.

DISCUSSION

As of 235 PM Thursday...

KEY MESSAGE 1... A strong cold front will bring light to moderate rain, seasonably gusty winds, and a sharp drop in temperatures Friday into Saturday.

A stationary cold front draped across the Midwest this afternoon will sharpen and then progress southeast into the Mid-Atlantic Fri morning. Although guidance varies slightly on the exact timing the cold front will enter central NC Fri afternoon, the general consensus is that the front will traverse our region in backdoor fashion (from VA as opposed to from the northwest). Ahead of the front, warm southwesterly flow will increase and support unseasonably warm and likely record breaking temperatures at RDU and FAY (see climate section below for daily records).

Although boundary layer moisture will be rather meager for air temperatures in the mid 80s to around 90, an EML over the central CONUS and Midwest will advect eastward and over the Carolinas by Fri morning, although weakening and modifying slightly. This will help support the development of weak instability on the order of 100-500 J/kg of SBCAPE over the Carolinas ahead of the front. With the overall lack of synoptic mid/upper level forcing through the afternoon, the primary forcing mechanisms will come from the front itself, and/or convective outflow outpacing the front and result in mostly anafrontal convective processes (elevated convection). This will greatly limit any strong to severe storms, although seasonably strong winds will certainly be possible with the passage of the front (30-40 kts). Weakly elevated instability and perturbations rippling through the seasonably moist band of moisture behind the front will provide our main precipitation for this event. Hi-res guidance is coming in wetter than global models and suggest within larger areas of 0.1 to 0.3", localized 0.5 to +0.75" will be possible, but entirely dependent on deeper convection developing behind the front.

KEY MESSAGE 2... Adverse fire weather conditions possible Friday and again on Saturday.

Although meteorological conditions will likely not overlap to result in typical fire weather concerns, the combination of unseasonably warm and record breaking temperatures, relative humidity values in the 30s, seasonably breezy southwesterly winds, and bordering on historic dryness within 100-hr fuels, may provide for an atypically hazardous fire weather day on Fri. This will be further complicated and especially hazardous around any ongoing fires by an abrupt wind shift from the front, or convective outflow, as it shifts south through the forecast area late Fri afternoon into the evening.

Dependent on the areal footprint of a wetting rain that occurs late Fri afternoon into Fri night, Saturday may also feature a typically unfavorable pattern for fire weather concerns with a northeast wind. However, gusty winds and widespread minimum RH values less than 25%, and possibly as low as the teens in the western Piedmont, will likely enhance fire weather concerns.

KEY MESSAGE 3... Widespread frost conditions likely with localized freeze possible Sun morning.

A chilly 1037mb Canadian high pressure system will shift southeast into our region and setup across NC and VA around daybreak Sunday morning. Low level thickness values will modify from Saturday and range between 1305 to 1315m on Sunday morning thanks to warming in the top of the layer but with the surface high overhead, favorable radiational cooling conditions will result in chilly temperatures. We adjusted lows downward a bit into the 28 to 34 range. These temperatures would be especially hazardous to any early budding plants/vegetation that are sensitive to the cold. The Frost/Freeze program for central NC will begin the morning of April 1st, at which time we will resume the issuance of Frost Advisories, Freeze Watches/Warnings. Until then, will continue to highlight this risk in the HWO and gridded weather forecast.

KEY MESSAGE 4... Dry weather is expected to return for the weekend through at least mid week resulting in a prolonged period of below average precipitation exasperating drought conditions and sustaining or prolonging the abundance of pollen in the air.

Dry weather is expected for the weekend through at least mid week with the next chance of rain arriving late in the work week and especially toward the weekend. This will likely mean the only measurable rain from March 17th through April 1st will be the limited QPF event on Friday.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

As of 125 PM Thursday...

There is reasonably high confidence in VFR through the 24-hour TAF period. Winds out of the southwest this afternoon will gust upwards of 18 kt. Some early afternoon MVFR ceilings are possible at FAY/RWI, but these lower ceilings should scatter out by 18-19z. LLWS is again expected tonight at all terminals, slowest and shortest at FAY, as a LLJ strengthens overhead. We cannot rule out a stray MVFR ceiling early Fri morning, but VFR should otherwise prevail. After some weakening of the winds tonight, gusts will pick back up Fri between 18-22 kt, especially Fri afternoon.

Outlook: A cold front will bring scattered showers and a few isolated storms Fri night, along with IFR-MVFR restrictions in post- frontal rain. NE winds behind the front will be gusty in the 20-30 kt range into early Sat. VFR should prevail through Tue.

CLIMATE

Record High Temperatures:

March 27: KGSO: 86/1921 KRDU: 87/2007 KFAY: 87/1946

Record High Minimum Temperatures:

March 27: KGSO: 60/2007 KRDU: 65/1949 KFAY: 65/1949

RAH WATCHES/WARNINGS/ADVISORIES

None.