textproduct: Raleigh

WHAT HAS CHANGED

As of 250 PM Wednesday...

* Nothing appreciable

KEY MESSAGES

As of 300 PM Wednesday...

1) A front, and focus for rain, will strengthen and become quasi- stationary near the border of NC and VA late tonight through Fri morning, with continued unseasonably mild/warm conditions to its south and throughout most of cntl NC.

2) Varying chances of rain late week into the weekend, with near- record temperatures possible Friday.

3) Below normal temperatures return early next week.

DISCUSSION

As of 300 PM Wednesday...

KEY MESSAGE 1... A front, and focus for rain, will strengthen and become quasi-stationary near the border of NC and VA late tonight through Fri morning, with continued unseasonably mild/warm conditions to its south and throughout most of cntl NC.

Low amplitude disturbances, within an energetic srn branch jet extending from the sern Pacific and srn Plains to the srn Middle Atlantic, will stream across and offshore VA/NC through Thu. Within that regime, a band of mid/upr-level-generated rain evident in regional radar data from TX to Middle TN to the srn Middle Atlantic, will edge sewd and across cntl NC with mostly Trace amounts tonight. Meanwhile, a backdoor front will develop and strengthen near the NC/VA border and become a focus for both low overcast and more substantial rain along and to its north on Thu, including a tenth to quarter inch amounts likely across the far nrn Piedmont and nrn Coastal Plain of NC (and higher amounts nwd into VA). The front will also separate continued unseasonably mild/warm temperatures to its south from much cooler ones to its north. In fact, forecast low temperatures the next couple of nights in cntl NC will be at or above the average high temperature for mid Feb, and the 60s-70s over cntl NC on Thu will likely be starkly contrasted by 40s-50s over VA.

KEY MESSAGE 2... Varying chances of rain late week into the weekend, with near-record temperatures possible Friday.

Overview: Aloft, the mid-level anti-cyclone will track ewd across the Gulf and Caribbean Thu-Sun, with cntl NC on the nrn periphery under generally swly-wly flow. A series of shortwaves will break off of the parent cyclone over wrn Canada, with a couple eventually tracking ewd across the region. As one s/w low lifts nwd from the upper MS Valley into wrn Ontario, another s/w will track ewd across the n-cntl Plains Thu and close off as it lifts enewd across the upper MS Valley and into the Great Lakes Thu night/Fri, while another s/w moves across the Intermountain West. The low over the Great Lakes will continue ewd across the Northeast Fri night/Sat, while the other s/w tracks ewd across the Rockies and Plains. The latter s/w will continue ewd across the MS Valley as yet another s/w could drop swd out of Canada and across the Plains Sat/Sat night. The details surrounding the subsequent evolution of these shortwaves vary amongst the available model guidance, but generally expect both to move across the Appalachians and mid-Atlantic through Sun night/Mon.

At the surface, as the initial occluded low weakens over the upper MS Valley on Thu, another low will emerge off the cntl Rockies and move ewd across the cntl Plains and into the mid-MS Valley. This now dominant low will then lift nnewd into the wrn Great Lakes Thu night/Fri, deepening as it absorbs the remnants of the initial low, while the attendant cold front moves quickly ewd across the OH and TN Valley regions Thu night. This low will then also occlude over the wrn Great Lakes on Fri, while the cold front continues ewd across the Appalachians and into the mid-Atlantic/Carolinas on Fri. A triple point low may develop as the front moves across the the mid- Atlantic, then continue offshore while the front slides ssewd across the area Fri/Fri night. The front should become quasi-stationary and generally W-E oriented across the Southeast US/Carolinas Sat. While timing and location vary amongst the medium-range guidance, another low may develop along the front over the lower MS Valley/Deep South Sat/Sat night, then track enewd along the front across the Southeast US/Carolinas and offshore Sat night/early Sun. This low is expected to deepen, potentially rapidly, thereafter. However, the track and strength of it Sun/Mon remains uncertain, resulting in continued low confidence in forecast details during that time. 3) Below normal temperatures return early next week.

Sensible Weather: Low temperatures Thursday night will be close to typical mid-February high temperatures. There will be the potential for record high overnight low temperatures on Friday, depending on how quickly temperatures drop Friday night. Have pulled back on the NBM chances of rain Friday, which still has a 60% chance of rain generally to the north of US-64 with 30-50% chances south of US-64. If the NBM is in fact overdoing the amount of precipitation, then temperatures could creep even higher on Friday, threatening record highs with values in the 70s and lower 80s. Low temperatures Friday night will be lower than Thursday night, but still well above normal. Saturday will be a bit of a transition day with the front across the area, so some cooler air will move into the region and the best chance of rain will be from US-64 to the south. Temperatures may drop below normal on Sunday as a surface low potentially develops off the Carolinas coast and rain continues across the eastern half of the area.

KEY MESSAGE 3... Below normal temperatures return early next week.

Much of the forecast for next week, especially wrt precipitation and winds Mon/Mon night, will depend on the evolution of the surface low along/off the mid-Atlantic/Carolina coast and the trough aloft. There is still a good amount of model variability and thus forecast uncertainty, however there is relatively high confidence temperatures will be below normal Mon and Tue, with nwly flow in the wake of the front/low and high pressure building swd across the Plains then progressing ewd. Temperatures could rise back to near- above normal by mid-week while the high gradually modifies as it tracks ewd across and out of the region.

AVIATION /00Z THURSDAY THROUGH MONDAY/

As of 655 PM Wednesday...

A band of light, mid-level-generated rain and associated minimal restriction to surface visibility, will overspread the nrn half of cntl NC overnight. A backdoor front will move to near the NC/VA border late tonight. An area of IFR-MVFR ceilings will develop mainly just to our north, along and north of that boundary, as will additional areas of rain, and persist into the first half of the day Thu (to around the end of the 18Z TAF period). FAY, where VFR conditions are forecast, should meanwhile remain well south of the front and focus for rain and flight restrictions through Thu.

Outlook: The front, and focus for rain and flight restrictions, will probably retreat nwd to near or north of the VA border Thu afternoon- evening, then settle swd and into the nrn NC Piedmont once again later Thu night-Fri morning. A chance of showers will accompany a trailing cold front across the region later Fri. That front and focus for the development of a couple of areas of low pressure will then stall over the Southeast and support periods of rain and additional flight restrictions over cntl NC this weekend.

RAH WATCHES/WARNINGS/ADVISORIES

None.

CLIMATE

Record High Temperatures:

February 19: KGSO: 74/1939 KRDU: 76/1939

February 20: KGSO: 74/1922 KRDU: 75/1939 KFAY: 82/2014

Record High Minimum Temperatures:

February 18: KGSO: 54/1981

February 19: KGSO: 55/1961 KRDU: 62/1938 KFAY: 62/1938

February 20: KGSO: 56/1939 KRDU: 62/1939 KFAY: 60/1939