textproduct: Columbia

WHAT HAS CHANGED

Rain chances for late this week and this weekend continue and should generally favor the western and northern Midlands. Aviation discussion updated for 06Z 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 /06Z TUESDAY THROUGH SATURDAY/

Brief restrictions possible near sunrise, especially at OGB and AGS but otherwise mostly VFR.

VFR conditions in place at all terminals currently with clear skies and generally light and variable winds. The overall synoptic pattern remains similar to yesterday with high pressure offshore and a relatively weak southerly to southeasterly low level jet. This should support relatively similar conditions early this morning to yesterday morning. While widespread restrictions are unlikely and not supported by guidance, brief restrictions remain possible at all terminals, although confidence is the highest at fog-prone AGS and OGB which also experienced restrictions yesterday morning. Any low clouds or fog will mix out relatively soon after sunrise with cumulus clouds developing around 5kft and SSE winds around 5 to 10 knots.

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 towards the end of the week.

CAE WATCHES/WARNINGS/ADVISORIES

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