textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 12Z TAF issuance.

KEY MESSAGES

- 1. Above normal temperatures likely into this weekend.

- 2. Rain chances increase late week onward, but drought conditions to persist.

DISCUSSION

Key Message 1: Above normal temperatures likely into this weekend.

Amplified east coast ridging and offshore surface high pressure this week lead to high confidence in above normal temperatures through the end of this week. Mid-May normals generally fall in the mid-80s, while blended guidance through Thursday yields highs in the low to mid 90s with small (less than 3 degree F) interquartile ranges. Temperatures may decrease just slightly into the upper 80s Friday into this weekend with a bit more moisture around, but should still remain above climatology. This is mainly in response to the upper ridge translating slightly eastward and better rain chances across the area, but more on that in Key Message #2. It should be noted that early season heat can contribute to an increased risk of heat- related illness, and much of the area will be in a Moderate Heat Risk through Thursday, with the threat decreasing Friday into the weekend.

Key Message 2: Rain chances increase late week onward, but drought conditions to persist.

Overall deterministic and ensemble guidance keep the Rex block in place off the east coast this week, but a slight shift eastward is expected in the second half of the forecast period. This should lead to increasing moisture over the Southeast from Thursday through Memorial Day as southwest flow strengthens aloft. Coupled with persistent low level southeast flow around the Bermuda high, PWAT values rise to just above normal, with GEFS mean values of 125-150%. The result should be increased chances for daily afternoon showers and thunderstorms, particularly given the expected strong heating and above normal temperatures previously mentioned. Additionally, some enhancement may occur across the northern and western portions of the forecast area closer to where the best moisture transport is, and where there is a higher likelihood of a few shortwaves moving through the flow. We're still a bit too far out to be talking about specific rainfall amounts, but the GEFS 50th percentile QPF through Saturday night ranges from only a few hundredths across the southeast Midlands to just under 0.75" in the western and northern Midlands with a gradient in between. As such, it appears that any rain we do get at least through Saturday will not have much impact on our ongoing drought conditions.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

VFR conditions are expected through majority of the TAF period, another round of patchy stratus and/or fog possible Wednesday morning.

Patchy fog is clearing AGS/OGB this morning, giving way to VFR conditions. The remainder of the day may see FEW cumulus and some passing cirrus as south to south-southeasterly winds pick up to 6-9 kts. These winds likely become light and variable again tonight and through the end of the TAF period. Early Wednesday morning, guidance indicates patchy stratus or fog could be possible mainly toward AGS/OGB, but some cirrus may be moving in as well which may limit this.

EXTENDED AVIATION OUTLOOK...Increased moisture may result in brief restrictions at the terminals due to low clouds and/or fog each day this week. Rain chances increase Thursday and into this weekend.

CAE WATCHES/WARNINGS/ADVISORIES

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