textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated forecast for 12z TAFs.

KEY MESSAGES

1. Patchy fog possible this morning followed by another day of warm temperatures and dry weather. 2. Rain returns by the end of the week, and a pattern change may be in store for the weekend.

DISCUSSION

Key message 1: Patchy fog possible this morning followed by another day of warm temperatures and dry weather.

Heights will continue to rise across the region as shortwave ridging slides from the Mississippi Valley into the Appalachians in advance of an upstream trough digging down the west coast. At the surface, high pressure will remain centered over the eastern Carolinas with light to calm winds overnight. This will promote fairly efficient radiational cooling with lows falling into the mid to upper 30s. Traditional cool drainage locations that are able to cool to or below the crossover temperature will have the potential to see patchy fog, some of which could be locally dense. The greatest coverage of fog is expected to remain south of the area, however. High clouds will stream across the area this afternoon with temperatures climbing back into the low to upper 60s.

Key message 2: Rain returns by the end of the week, and a pattern change may be in store for the weekend.

Guidance continues to signal a regime change by next weekend. Long-range ensembles are in broad agreement on the persistence of quasi-zonal flow aloft Wednesday through early Friday, but with steadily increasing synoptic forcing at the low- and mid-levels. The surface pattern during this time honestly bears a striking resemblance to the Bermuda High setup we typically see during late summer...with broad high pressure established over the western Atlantic, and no strong dynamical features aloft, at least over the Southeast CONUS.

By Thursday, the upper pattern across the Midwest should begin to amplify. Guidance doesn't have a great handle on it yet, but a pre-existing upper low centered over the upper Midwest is depicted interacting with a weaker developing trough axis, originating over the Rocky Mountain front range but rapidly ejecting across the southern Great Plains and winding up somewhere over the eastern Great Lakes or upper Ohio Valley by Friday afternoon. That this feature will result in surface cyclogenesis is virtually a given based on the latest round of global ensembles; where that will happen is unclear, but ultimately unimportant: for the Carolinas, we'll essentially find ourselves in a massive warm sector either way, and the resultant moisture flux should result in widespread rainfall Thursday through Friday. QPF response looks limited at this time - with even the 95th percentile of rainfall totals for this period likely being too low for serious hydro concerns.

What happens after that is anyone's guess. Ensembles sort of agree that the cyclone will begin to occlude over the Ohio Valley (or the southern Great Lakes, or the Alleghenies), after which the attendant cold front will become oriented parallel to the upper flow and wash out somewhere over the Carolinas early next weekend. Some guidance then reactivates the boundary as a warm front on Sunday, or even depicts cyclogenesis directly over the Carolinas, resulting in another round of rainfall in the D6-7 timeframe. Other guidance (primarily the EC ensembles and ) keeps the front more progressive, resulting in drier and markedly cooler weather Sunday night and beyond. The details are not yet clear; confidence will only improve with time.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

At KCLT and elsewhere: VFR conditions will prevail through the TAF period at all terminals. A few isolated instances of patchy fog cannot be ruled out through sunrise, but coverage is expected to remain isolated and best and generally confined to cool drainage locations. Otherwise, high clouds will continue to stream across the area today with no operational impacts. Light to calm winds this morning will increase to 6-10kts through this afternoon out of the south/southwest. Winds should remain high enough tonight to limit fog development.

Outlook: Nocturnal fog/stratus can't be ruled out near daybreak Thursday. Otherwise VFR through midweek. Rain may return to the area by Thursday or Friday.

CLIMATE

STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 76 1927 8 1958 57 1891 -3 1958 KCLT 79 1927 20 1958 62 1883 7 1958 KGSP 75 1976 25 1958 58 1976 1 1958 1927

RECORDS FOR 02-18

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 72 1897 15 1958 55 1891 0 1958 KCLT 78 2011 25 1979 62 1891 5 1958 1891 KGSP 78 2011 26 1979 55 1975 2 1958

RECORDS FOR 02-19

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 72 2014 16 2015 54 1951 3 2015 KCLT 76 2014 26 2015 55 1961 8 1958 1939 KGSP 75 2014 30 2015 55 1961 9 1958 1916 1900 1900 1911

RECORDS FOR 02-20

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 75 1939 26 1908 54 2018 4 2015 KCLT 77 2014 31 2015 59 1939 7 2015 1890 KGSP 75 2014 33 2015 57 1939 9 2015 1986

RECORDS FOR 02-21

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 77 1986 12 1896 60 2018 8 1896 KCLT 80 2018 32 1896 61 2018 6 1896 KGSP 77 2023 35 1978 62 2018 9 1896 2018 1902

RECORDS FOR 02-22

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 77 2018 27 1939 58 2018 2 1963 KCLT 80 2018 33 1963 62 2018 12 1963 1897 KGSP 78 2023 35 1969 60 2018 10 1963 2018 1963

RECORDS FOR 02-23

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 76 1982 29 1989 54 1922 10 1939 KCLT 80 2023 29 1901 66 2023 19 2009 1978 1963 KGSP 79 2023 36 1966 64 2023 15 1963 1939

RECORDS FOR 02-24

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 77 1930 26 1947 54 2018 6 1967 KCLT 80 2018 26 1889 56 2018 16 1967 1982 1992 1930 KGSP 80 2018 33 1901 57 1909 15 1967 1901

GSP WATCHES/WARNINGS/ADVISORIES

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