Like a radiant spring flower, a brilliant young singer/songwriter blossomed right before the transfixed eyes of a cheerful Napa Valley Opera House audience last Saturday night.

It’s not that he hadn’t already excited a Napa audience previously. Last spring, when Spencer Day opened Rufus Wainwright’s wine country debut in the same venue a packed house gave the modern-day minstrel — a last minute addition to the program — a rip-roaring standing ovation.

But last weekend, Day was in control of the proceedings. To that end, he brought along longtime collaborator/arranger/cellist Yair Evnine and a first-class rhythm section — Jon Evans, bass, and Scott Amendola, drums) to flesh out a fascinating two-hour program showcasing a wealth of the headliner’s newest compositions, material just recorded for a new CD being readied by a major label for release next spring.

Just for good measure, the 30-year-old entertainer threw in a handful of songs written by others, ranging from a haunting rendition of a vintage Paul Simon ballad, “American Tune,” to a Chet Baker-styled version of the WWII-era Harry Warren/Mack Gordon standard, “There Will Never Be Another You.”

This audience member, for one, was impressed most with how Day’s delivery had improved, in that he was much more self-assured, certainly at ease as he joked with the crowd about his initial attire (“a newsy paperboy outfit to replicate the Depression” was how he described his newsboy cap and suspenders attire). This was from somebody whose pre-performance stage fright not all that long ago used to nauseate him.

No more, for here was Day chatting and joking with the crowd, rather than retreating as usual into the grand piano on which he accompanies himself.

Additionally, his material seemed to take on added importance, due in part to the fact that the new songs strike a chord within all of us, for this is a contemporary songwriter with a lot on his mind, one who’s able to offer salient comments on the passing scene.

With a bittersweet edge, he mourns love lost in a clever plea, “Till You Come To Me,” and laments the passage of “Summer,” which “fades as fast as a summer tan.” 

The new material includes a pop song with a country hook about delicately walking the line, “Everybody Knows,” and a hauntingly melodic comment about the battlefield of love, “Little Soldier.”

Using an autobiographical brush, Day’s painted a fascinating portrait of young man named “Joe” breaking with familial ties in order to find his own voice far from home. That search extends to another touching folk song, “Vagabond” (the title track of the forthcoming CD), in which the singer admits “anywhere the wind blows, that’s where I belong, I keep movin’ on.” Here Day brought to mind Brooklyn-based composer Craig Carnelia who mines the everyday human condition for his brilliant word pictures. To this listener, Day comes close to Carnelia in his descriptive lyrics, only wearing a bit more vulnerable heart on his sleeve. On several occasions, I felt myself thinking this is contemporary American “morna” without the wrist-slashing evocation of, say, Leonard Cohen. (Although Day did bring his Napa performance to a close with a terrific rendition of Cohen’s “Hallelujah,” the first time he’s performed that song for an audience.)

Influenced by everything from Broadway musicals to jazz, pop to gospel, country to R&B, Spencer Day brings the best of them all to play in both song and performance.

There was a taste of Appalachia with the revisionist gospel feel of “Ophelia,” and the great Richard Rodgers showed up in “Something Good,” a song the composer added to the film score of “The Sound of Music” following the death of Oscar Hammerstein II.

But it’s Day’s songs that stick in mind now, long after the final notes were sung — that rainy day lament, “Out of My Hands,” the sensuality of “Close the Door” and the honesty of not fitting in demonstrated by the goings-on at “Ernie’s Hollywood Party.”

After a decade of playing small clubs, dining rooms and such from coast to coast, Spencer Day is poised for well-deserved success. When those in Saturday night’s audience see him introduced by David Letterman one night soon, all can boast of the night they saw Day launch the next stage of his career here in wine country. Those who didn’t attend the Opera House show, well, they can enjoy the televised moment and just imagine what might have been.

But it’s not too late. Day is appearing in the Rrazz Room of San Francisco’s Hotel Nikko, 222 Mason St., through Sunday. For tickets and information, call (866) 468-3399.