Western Digital Corporation (NASDAQ: WDC) ended Thursday, December 18, 2025, with a sharp rally that extended—modestly—into after-hours trading, keeping the AI-infrastructure “storage trade” firmly in the spotlight heading into Friday’s session.
By the closing bell, WDC finished at $175.01, up 5.26%, after trading in a wide range between $174.43 and $181.49 on heavy volume (about 9.15 million shares). [1]
After the close, shares ticked higher to roughly $176.30 (+0.74%) in late evening trading, with after-hours volume reported near 944.8K shares. [2]
The big question for investors now: was Thursday’s move a one-day sympathy surge—or another leg in a broader, catalyst-driven run that still has room to run into year-end and beyond?
WDC after the bell: the numbers that matter
Here’s the quick snapshot of Western Digital stock performance after the bell on Dec. 18, 2025:
- Regular session close: $175.01 (+5.26%) [3]
- Day’s high / low: $181.49 / $174.43 [4]
- After-hours quote: about $176.30 (+0.74%) as of the late update [5]
- After-hours volume: ~944.8K [6]
This matters because it shows two things simultaneously:
- Momentum is still strong (the stock held gains into extended trading), and
- Volatility is not going away (the intraday range was large, and Friday brings its own potential volatility catalysts).
Why Western Digital stock surged Thursday: the “storage + AI” trade got a fresh jolt
Western Digital didn’t report earnings Thursday—but it benefited from a powerful combination of sector and macro tailwinds that dominated market coverage on Dec. 18.
1) Micron’s blowout outlook reignited AI-linked chip enthusiasm—and pulled storage names higher
The dominant catalyst across markets Thursday was Micron Technology’s upbeat forecast, framed by many outlets as a sign that AI-driven demand (and supply tightness in parts of memory) remains strong. [7]
That matters for WDC because investors often treat the broader data-center buildout as a single theme spanning chips, memory, networking, servers—and storage. On Thursday, that renewed confidence helped lift AI and related tech names, supporting a rebound in the Nasdaq. [8]
2) Softer inflation data improved the “rates backdrop” for tech
Markets also reacted to a cooler inflation update. The AP’s recap noted that stocks gained after an encouraging inflation report, and Micron’s results helped “AI stocks stop their slide.” [9]
For high-beta tech names like WDC, a friendlier interest-rate narrative can amplify risk-on positioning—especially when the market already has a strong thematic story (AI infrastructure) to buy.
3) Western Digital has become one of 2025’s standout winners—momentum investors are paying attention
A Reuters analysis of 2025 S&P 500 performance highlighted that Western Digital and Seagate have been among the year’s biggest gainers, tying the move to continued AI infrastructure spending by hyperscalers and rising demand for high-capacity storage.
Momentum tends to feed on itself late in the year—especially when index events and options-market dynamics are also in play.
The structural story: Western Digital is now a pure-play HDD company after the SanDisk split
Investors evaluating WDC in late 2025 are not looking at the same corporate structure they knew a few years ago.
Western Digital completed the planned separation of its Flash business in February 2025. [10]
The spun company, SanDisk, began trading as an independent public company on Nasdaq under the ticker “SNDK.” [11]
This matters because it sharpened WDC’s identity: a concentrated bet on hard disk drives (HDDs) and high-capacity storage demand—areas increasingly framed as essential infrastructure for AI-era data growth.
In its February 2025 Investor Day materials, Western Digital emphasized its AI-driven storage opportunity and noted it was testing HAMR technology with hyperscale customers—a key point because HAMR is often viewed as a next-generation path to higher HDD capacity. [12]
A near-term catalyst still ahead: Nasdaq-100 inclusion and the “index effect”
Even though Thursday’s move was largely about sector momentum, there’s another date investors have circled:
Western Digital is slated to be added to the Nasdaq-100 as part of annual index changes effective December 22, 2025, per Nasdaq’s official announcement. [13]
Why that matters heading into Friday’s open:
- Index additions can create forced buying from funds and products that track the Nasdaq-100 (directly or indirectly).
- The effect can show up in the days before the rebalance, depending on how passive and active managers choose to position.
It doesn’t guarantee upside—but it can influence flows, volume, and volatility into next week.
Analyst forecasts: where Wall Street thinks WDC could go next
After a year like 2025, forecasts start to diverge: some analysts see more upside from structural AI storage demand; others worry about how much good news is already in the price.
One widely followed snapshot (compiled from multiple analysts) shows:
- Average 12-month price target: ~$186.96
- High / low targets: $250 / $135
- Consensus skew: predominantly Buy (with a smaller hold camp) [14]
That same compilation lists recent research actions around mid-December, including maintained Buy ratings and notable targets from major firms. [15]
The takeaway going into Friday: even after the surge, the Street’s “base case” in that dataset still implies some upside from Thursday’s close—while acknowledging a wide range of outcomes.
What to know before the stock market opens Friday, Dec. 19, 2025
Thursday’s close is only half the story. Friday morning has multiple catalysts—some WDC-specific (positioning, flows), others marketwide (macro, central banks).
1) Key U.S. economic events on Friday morning
According to MarketWatch’s calendar, the top scheduled U.S. items include:
- 8:30 a.m. ET: New York Fed President John Williams TV appearance
- 10:00 a.m. ET:Existing home sales (Nov.)
- 10:00 a.m. ET:University of Michigan consumer sentiment (final) (Dec.) [16]
For the two 10:00 a.m. releases, Investing.com’s calendar shows expectations such as:
- Existing home sales forecast:4.15M vs 4.10M prior [17]
- Michigan sentiment forecast:53.5 vs 53.3 prior [18]
Why WDC investors should care: housing and sentiment aren’t directly tied to HDDs, but they can move rates, the dollar, and risk appetite—which often matter for high-momentum tech.
2) Friday is a quarterly “triple/quadruple witching” expiration—expect heavier volume and sharper swings
Dec. 19, 2025 is one of the quarterly expiration Fridays commonly called triple witching / quadruple witching, when multiple major derivatives contracts expire and can amplify trading volume and volatility. [19]
For a stock like WDC—already volatile, already heavily traded, and sitting near major round-number levels—expiration dynamics can exaggerate intraday moves, particularly into the close.
3) Watch Micron follow-through and the “AI complex” tone
Because Thursday’s rally was tightly linked to renewed enthusiasm around AI-related semiconductors and infrastructure, a key “tell” on Friday will be whether the market continues to buy that theme—or fades it.
If chip leaders extend gains, storage names can continue to ride the wave. If the AI complex sells off (profit-taking, rate jitters, or expiration effects), WDC can feel it even without company-specific headlines.
4) Levels investors are likely watching after Thursday’s spike
Using Thursday’s tape as a reference:
- $175 (the close) is an immediate “line in the sand” in the very short term. [20]
- The $181–$182 area (Thursday’s high zone) is the near-term breakout test. [21]
- The after-hours $176 area suggests dip buyers were still active post-close. [22]
These aren’t guarantees—just the obvious spots where traders often anchor.
5) The bigger setup into next week: Nasdaq-100 effective date is Monday
Friday is the final session before the Nasdaq-100 reconstitution becomes effective Monday (Dec. 22). [23]
That can keep attention on WDC even if Friday itself turns choppy.
Bottom line for Friday’s open
Western Digital stock enters Friday, Dec. 19, 2025 with:
- Strong upside momentum from Thursday’s surge,
- A small but notable after-hours extension, and
- A dense calendar of macro catalysts plus quarterly options expiration dynamics, which can add volatility even when the fundamental story remains intact.
If the market keeps treating AI infrastructure as the dominant theme—and if index-related positioning stays supportive—WDC could remain in focus into next week. If macro headlines or expiration flows hit risk appetite, expect bigger intraday swings than usual.
References
1. www.investing.com, 2. www.marketwatch.com, 3. www.investing.com, 4. www.investing.com, 5. www.marketwatch.com, 6. www.marketwatch.com, 7. www.reuters.com, 8. apnews.com, 9. apnews.com, 10. www.westerndigital.com, 11. www.sandisk.com, 12. www.westerndigital.com, 13. www.nasdaq.com, 14. www.investing.com, 15. www.investing.com, 16. www.marketwatch.com, 17. www.investing.com, 18. www.investing.com, 19. www.investopedia.com, 20. www.investing.com, 21. www.investing.com, 22. www.marketwatch.com, 23. www.nasdaq.com
