textproduct: Raleigh

SYNOPSIS

High pressure will build across and offshore the Middle Atlantic through tonight, ahead of a warm front that will retreat northward and across NC on Friday. A strong cold front will sweep through the region Saturday night, followed by a reinforcing one on Sunday.

NEAR TERM /TODAY AND TONIGHT/

As of 115 AM Thursday...

* Lower highs but still well above seasonal averages

* Fog/stratus possible late tonight to early Fri

High pressure near the Delmarva region will bring a "cooler" day compared to Wed. The cold front is forecast to reach portions of upstate SC this morning and afternoon. An ENE to ESE flow will be favored today with the high to the northeast. While we say it will be cooler, we mean that only in a relative sense from what we experienced Wed. Highs will still be some 15 to 20 degrees above normal in the low/mid 60s central/north to upper 60s to near 70 across the south.

Tonight, the surface high will shift off to near New England. The front to our south is then forecast to slowly migrate north as a warm front. Meanwhile, low pressure tracking into WI and low-level ridging off the SE US will promote increasing WAA and isentropic ascent atop the slow-moving frontal zone. This should favor the development of fog/stratus, especially across the Piedmont, Triad, and Sandhills. Some guidance, such as the HRRR/HREF, suggest the potential fog even in the Coastal Plain. Some patchy light rain/drizzle is also possible over the Triad early Fri within a 3-4 kft saturated layer. Low temperatures should dip into the mid to upper 40s, except low 40s NE.

SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/

As of 115 AM Thursday...

* Weak in-situ CAD regime possible across NW Piedmont with early morning drizzle

* Rain chances increasing, with best potential over the western Piedmont late Fri and Fri night

A surface high off New England to start Fri will shift off into the North Atlantic. Meanwhile, a southward moving frontal zone from the Central Plains into the Upper Great Lakes is forecast to reach the lower MS valley region as a secondary low pressure tracks into the TN valley by Sat morning.

A period of weak in-situ CAD could develop to start Fri over the Triad and far NW Piedmont as WAA atop the retreating frontal zone brings light rain/drizzle. Most CAM solutions bring this light precipitation during the early to late morning hours, although the Canadian regional RDPS keeps that chance in until the afternoon. That said, highs across the NW could be cooler than presently advertised. The MET/MAV show 61-62 versus 65-67 in the NBM. Elsewhere, fog/stratus are favored to start the day, though confidence on exactly how extensive is still not certain. It would appear the best chance would be across the Sandhills, central Piedmont and western Piedmont, though HREF/HRRR suggest all of central NC. Regardless, once the frontal zone lifts north, most of the area should be in the warm sector with southerly flow taking over once the stratus can erode. With anomalous ridging still in place, highs should rebound from Thu to the low/mid 70s east of the Triad.

As for rain chances, the first half of the day should be largely dry, outside of some patchy light rain/drizzle in the NW. A better chance of rain may come Fri night to early Sat as the aforementioned low pressure brings increasing moisture transport into the region ahead of the Midwest frontal zone. The highest probabilities for rain are over the west and northwest Piedmont, in conjunction with better forcing and moisture. Rainfall amounts up to a quarter inch may be possible in the NW by early Sat, with only trace amounts to the east and southeast. Record lows may exist Fri night with upper 50s to low 60s.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

As of 115 AM Thursday...

Low pressure will be over Tennessee Saturday morning, with a warm front extending east across the mid-Atlantic states and a cold front extending south towards the Gulf coast. As the low moves northeast, this will keep likely pops around the Triangle and to the north and west, but showers should remain isolated to scattered to the southeast during the daytime hours. As the cold front finally passes over the Appalachians Saturday night, this should bring widespread rain to all locations overnight. With the primary cold front along the Atlantic coastline by Sunday morning, the bulk of the rain should come to an end by then, although a secondary cold front will keep an isolated shower in the forecast for much of Sunday. Wind gusts up to 30 mph will be possible both Saturday and Sunday afternoon. High pressure will then move across the southern United States, resulting in a dry forecast for Monday and Tuesday. Models are showing some differences in the potential for a coastal low developing on Wednesday, but have included a slight chance of a shower in the forecast Wednesday afternoon.

All stations will have a chance to break the record high on Saturday, with highs in the 70s and even pushing 80 in some locations (see the climate section below for more information). Record warm minimum temperatures will also be possible on Saturday. Once the cold front comes through, Sunday will be a transition day, with highs back into the 50s and low 60s, then highs tumble into the 40s on Monday before easing back into the 50s on Tuesday and Wednesday. Sunday night and Monday night will be the widespread nights with lows below freezing.

AVIATION /12Z THURSDAY THROUGH MONDAY/

As of 608 AM Thursday...

A backdoor front have moved south of the terminals this morning. In its wake, winds will shift out of the ENE at 5 to 8 kt. Tonight, moisture builds back north as return flow sets in. Moist upglide in the low-levels atop the stable frontal zone will favor stratus and fog over central NC early Fri morning. Right now, guidance is not in the best agreement on location of stratus and low visibilities so overall confidence is not too high. However, from a pattern perspective, it would appear the best chance of mainly low stratus, MVFR to LIFR, would be at GSO/INT, where there is a deeper saturation centered around 925-mb. Conversely, it would appear a mix of stratus and possible fog is more favored at the eastern sites of RDU, FAY, and RWI, where the 925-mb layer is not as deeply saturated, favoring potential fog. For now, given the uncertainty, opted for prevailing MVFR at GSO, INT, RDU, and RWI, with tempo groups for IFR at RDU and LIFR at FAY/RWI, mainly between 08-12z Fri.

Outlook: Areas of light rain are possible Fri and Fri night, mainly over the Triad terminals. Areas of fog/stratus are again possible Sat morning. A cold front moving through Sun will favor increasing rain chances Sat into Sun, along with potential sub-VFR conditions and gusty/shifting winds, which may cause mechanical turbulence.

CLIMATE

Record High Temperatures:

January 9: KRDU: 73/2008 KFAY: 77/1930

January 10: KGSO: 73/1949 KRDU: 75/1930 KFAY: 79/1930

Record High Minimum Temperatures:

January 10: KGSO: 58/1937 KRDU: 63/1937 KFAY: 59/1937

RAH WATCHES/WARNINGS/ADVISORIES

None.