textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated for the new Aviation Discussion.

KEY MESSAGES

1. Our late-Spring-like weather pattern will continue with near-record warm temperatures today. A few thunderstorms will be possible this afternoon and evening, but the risk of severe weather is low through tonight. 2. Very warm with mainly diurnal convection Saturday through at least the middle of next week.

DISCUSSION

Key message 1: Our late-Spring-like weather pattern will continue with near-record warm temperatures today. A few thunderstorms will be possible this afternoon and evening, but the risk of severe weather is low through tonight.

The overall weather pattern continues to resemble something more typical of late spring, with an upper anticyclone and sfc high off the Southeast Coast and a deep trof over the Rockies through tonight supporting a gradually improving southerly flow across the region. The warm temperatures will be the main story, with mild overnight lows, and highs typical of mid-May. The records for Friday look to be on the low side...not quite outliers...but breakable considering what we have in the forecast. Meanwhile, it stands to reason that the longer this pattern persists, eventually we are going to be able to develop spring-like instability in the afternoon. The new NBM raises the dewpoint Friday afternoon another few degrees, perhaps enough to overcome weak capping. The latest RAP shows mixed-layer CAPE upwards of 1500 J/kg which would support the development of a few thunderstorms around peak heating, though the CAMs are still not particularly keen to develop much more than isolated/scattered showers across the Blue Ridge. If we manage a storm or two, the risk for severe weather remains low.

Key message 2: Very warm with mainly diurnal convection Saturday through at least the middle of next week.

A high-amplitude upper pattern over the weekend...characterized by a deep trough across the West, and a ridge along the East Coast...will evolve into a split flow regime early next week, as an upper low closes off over Baja, and northern stream height falls progress across the Great Lakes into New England. These height falls are expected to drag a weakening frontal zone into our CWA for Sunday. In the interim, a warm sector regime will remain firmly in place Saturday/Sat night, with unseasonably warm (15+ degrees above climo) and humid conditions expected to support scattered deep convective potential within broad warm advection regime Saturday. Buoyancy will certainly be robust considering the time of year...sbCAPE AOA 1000 J/kg Sat afternoon, but modest deep layer shear of 20-30 kts will be very marginal for an organized/severe storm potential. PoPs for showers ramp up to likely on Sunday as the front enters the picture, with scattered thunderstorms also expected. Enhanced cloud cover is expected to somewhat limit the instability Sun afternoon, but shear is also expected to increase to 30-40 kts. This may slightly increase the prospect of a few severe storms developing Sun afternoon.

Little air mass change is anticipated in the wake of the weak front early next week, as the flow aloft flattens with height falls expected to impact areas to our west and north. In fact, a humid and very warm...warm sector regime is expected to return no later than Tuesday and persist through the end of the forecast period. Near-record max temps are expected in the Tue/Wed time frame, with isolated-to-widely scattered, mostly diurnal showers and some thunderstorms in the forecast Monday through Wednesday. Forecast shear/buoyancy parameters are unimpressive in terms of any severe storm potential. PoPs increase and temps decrease a bit Wed night/Thursday, when southern stream upper low may begin to impact the region.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

At KCLT and elsewhere: Much like yesterday morning, another round of low stratus is currently advancing northward from CAE's fcst area. KCLT and KAND appear to have the best chance of seeing re- strictions again this morning, but it's looking more likely that they will remain VFR. The warming boundary layer should lift any lower clouds by late morning. Sct convection may develop over the fcst area this afternoon/evening, but the CAMs have been trending towards less coverage with the past few runs. Thus, I removed the PROB30s for -TSRA for our taf sites except at KAND, where PoPs are a bit higher later tonight into early Saturday. Otherwise, winds will be light and VRB to calm thru most of the morning. They will pick up from the S/SW during the afternoon and remain S/SW thru the evening. It's looking more likely that we'll see more widespread restrictions Saturday morning. So, I have MVFR to IFR cigs and MVFR visby at all our taf sites beginning around 09z on Saturday.

Outlook: The spring-like weather pattern will persist over the next several days with patchy fog/low stratus expected each morning. A stalling front will likely bring showers and associated flight re- strictions over the weekend.

CLIMATE

RECORDS FOR 03-06

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 78 1908 28 1960 58 1961 5 1960 KCLT 80 2022 33 1901 62 1961 10 1960 KGSP 79 1974 37 1948 63 1961 16 1960 1915 1901

RECORDS FOR 03-07

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 82 1974 23 1920 61 1956 15 1960 KCLT 85 1974 30 1899 63 2022 14 1899 1956 KGSP 83 1974 36 1920 62 1961 13 1901 1901 1956

RECORDS FOR 03-08

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 81 1974 23 1996 57 1921 8 1920 KCLT 84 1974 36 1989 59 1946 16 1920 KGSP 84 1974 35 1899 56 1921 14 1901 1899

RECORDS FOR 03-09

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 80 1974 22 1932 57 1964 8 1996 KCLT 83 2009 30 1960 62 1925 16 1996 1974 1921 1925 KGSP 85 2009 29 1960 60 2009 16 1996 1921

RECORDS FOR 03-10

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 76 1974 29 1932 58 1903 10 1996 1932 KCLT 82 1974 36 1924 59 1903 17 1932 KGSP 84 1974 39 1924 58 2009 17 1932 1997

RECORDS FOR 03-11

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 79 1967 29 1924 55 2016 14 1934 1925 KCLT 83 2015 37 1960 60 1986 22 1969 2009 1934 1990 KGSP 84 2009 34 1960 60 1986 17 1969

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...None. SC...None.